atoms: building blocks of matter chapter-3 1. atoms: building blocks of matter main concepts 1)...
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Atoms: Building Blocks of MatterChapter-3
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Atoms: Building Blocks of Matter
Main Concepts 1) Development of Modern Atomic Theory
Famous Dead Guys
2) Structure of the Atom
3) Compounds, Elements, Atoms, Ions, and Isotopes
4) Atomic Mass and the Mole
5) Introduction to stoichiometry: Calculations involving mass, moles,
particles, and volume2
Early Atomic Theory (450 - 380 BC)Who did it? • Aristotle , Socrates, Plato, Empedokles, et al.
What did they do?• Established four elements that make up all the
structures in the world: fire, air, water, earth (Empedokles) and the four basic properties that make up all matter, there were four basic properties: hot, cold, wet, and dry.
• Developed the continuous theory of matter: “all matter can be divided and subdivided into smaller and smaller pieces without limit.”
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Early Atomic Theory (450 - 380 BC)
How did they do it?
Thought about it and talked about.
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The Four Elements
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Early Atomic Theory (450 - 380 BC)
Who did it?• Democritus
What did he do?• Proposed the Discontinuous Theory of Matter
“matter was discontinuous, like a clump of grapes, it could be divided in half repeatedly until eventually only one grape was left that could not be divided.”
• Democritus called this smallest particle of matter an atom (from the Greek atomos, meaning indivisible).
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Early Atomic Theory (450 - 380 BC)
How did he do it?• Thought about it and talked about
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Discontinuous Theory of Matter
Major points: 1. All matter is composed of atoms, which are
tiny bits of matter too small to be seen. These atoms cannot be further split into smaller portions.
2. There is a void, which is empty space between atoms.
3. Atoms are completely solid.4. Atoms are homogeneous,
with no internal structure.5. Atoms are different in their size,
shape, and weight (later added by Epicurus). 8
Development of Modern Atomic Theory
• The Continuous Theory of Matter held by Aristotle and Plato was the prevailing theory of the time.
• Because Democritus had no proof for his theory of the atom, the idea of the atom was strongly opposed by these men and would not reappear until the 18th century nearly 2000 years later.
• Democritus’ Model of the Atom
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Roger Bacon (1214-1294)
Who did it? • Roger Bacon: 13th century English
philosopher and scientist.
What did he do?• was the first to formulate and advocate the use
of the scientific method converting science from a philosophical to an experimental study of the world.
How did he do it?• through experiments on optics, hydraulics, light,
and the manufacture of gunpowder.10
Alchemists (1400 – 1650)
Who? Alchemists
What? Developed many experimental methods and equipment and built an extensive body of chemical data.
How? While attempting chemical transmutation (turning base metals into gold); other goals of alchemists were to find a universal solvent, and the elixir of life.
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Antoine Lavoisier 1744
Who? Antoine Lavoisier
What? Law of the Conservation of Matter/Mass “matter can not be created or destroyed in ordinary chemical or physical changes”.
How? By taking careful weights of reactants and products during reactions of gases, water, and combustion
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Joseph Proust (1799)
Who? Joseph Proust
What? Law of Definite Composition/Proportions a chemical compound contains the same elements in exactly the same proportions (ratios) by mass regardless of the size of the sample or source of the compound.
How? Through studies of copper carbonate, the oxides of tin, and the iron sulfides: comparing the compounds produced in the lab to natural occurring compounds. 13
John Dalton (1803 )
Who? John Dalton
What? Developed Dalton’s Atomic Theory: the start of modern atomic theory.
How? Through experiments on the properties of gases and his law of multiple proportions.
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John Dalton
Law of Multiple Proportions: “when the same two elements combine to make two different compounds, and if the masses of one of the elements in the two compounds are the same, then the ratio of the masses of the other element in those compounds will be a ratio of small whole numbers.”
• CO and CO2
• NO3 and N2O3,
• FeCl2 and FeCl3
• N2O3 and N2O4
• NO3 and N2O2
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Law of Multiple Proportions
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Dalton's Atomic Theory:
Dalton's Atomic Theory:
1) All matter is composed of extremely small particles called atoms.
2) Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties.
3) Atoms cannot be subdivided, created, or destroyed.
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John Dalton
4) Atoms of different elements can combine in simple, whole number ratios to form chemical compounds.
5) In chemical reactions, atoms are either combined, separated, or rearranged.
a) Combination: A + B AB
b) Separation: AB A + B
c) Rearrangement: AB + CD AD + CB
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John Dalton
Dalton’s Atomic Model Dalton’s model of the atom was accepted because it was based on the Laws of Conservation of Mass, Definite Composition, and Multiple Proportions.
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John Dalton
• Dalton’s atomic theory is still used as the basis for modern atomic theory even though some of his statements are not true today.
Disproved:
2) Atoms of a give element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties.
3) Atoms cannot be subdivided, created, or destroyed.
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William Crookes 1877
Who? William Crookes
What? Discovered “cathode rays”, the first evidence of electrons.
How? Experiments with gases using a vacuum tube now called “Crookes Tube” or “Cathode Ray Tube.” Observed different gases glowed with different colors, cast shadows opposite the cathode, and were deflected by magnetic and electric fields.
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William Crookes 1877
Conclusions:
1) Observed radiation originated at the cathode, acted like light, and traveled in a straight line unless deflected by a magnetic or negative electric field (negative charge). Crookes called this radiation, “cathode rays”.
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J. J. Thomson 1898
Who? J. J. Thomson
What? - Discovered the electron: the first subatomic particle)
-Calculated the charge to mass ratio of the electron
How? Experiments using a modified Crookes Tube.
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Thomson’s Experiment
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J. J. Thomson
Thomson’s Experiment:1) confirmed Crookes’ experimental results
2) proved that “cathode rays” were actually negatively charged particles called electrons
3) calculated the charge to mass ratio of the electron (1.76 x 108 coulombs/g) by measuring the amount of deflection and the energy.
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J. J. Thomson
4) determined that this ratio was always constant regardless of the type of metal or gas used.
5) concluded that cathode rays were actually negatively charged particles and proved that the atom is not indestructible but made up of smaller particles called electrons and an equal amount of positive material.
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Thomson’s Atomic Model
• The atom was not homogeneous but consisted of negatively charged particles called electrons and an equal amount of positive material.
• Plum pudding model. 27
Max Planck 1900
Who? Max Planck
What? Determined energy is quantized, founder of quantum theory,
How? Trying to invent a better lightbulb through experiments with hot metals by maximizing the amount of light while minimizing the amount of energy (heat).
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Max Planck
• When solid objects are heated, they emit
radiation as seen in the red glow of an electric stove burner or the bright white light of a tungsten light bulb.
• Classical physics could not account for different metal objects glowing with the same color at the same temperature.
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Max Planck
• Planck solved the problem by assuming that electromagnetic energy could be emitted only in quantized form: ie, energy (light) has particle - like properties and therefore can behave like matter.
• Energy can be either released or absorbed by atoms only in discrete “bundles” of some minimum size called quantum (fixed amount). A “quanta” of radiation (a single particle of light) was the smallest quantity of energy that can be emitted or absorbed as electromagnetic radiation.
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Max Planck
• The energy of one quanta of radiation is given by: E = h, where: E = energy h = 6.6 x 10-34 J/hertz (Planck’s constant) = is the frequency of the radiation.
• Since c = and E = h, then E = hc/
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Heated Iron Bar
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Pour of Molten Steel
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Albert Einstein 1905
Who? Albert Einstein
What? Explained the photoelectric effect
How? Used Planck's equation in his study of light, E = h
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Albert Einstein
• Photoelectric Effect: When a metallic surface is exposed to light above a threshold frequency (energy) that is specific to the surface of the material, the light is absorbed and electrons are ejected producing electric current.
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The Photoelectric Effect
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Albert Einstein
• Proved that the energy of ejected electrons was dependent upon the frequency of the light as described in the Planck’s equation E = h. One electron was ejected for each quanta of light absorbed.
• Proved that light energy was only emitted and absorbed by electrons in discrete amounts or quanta. This quanta of light energy soon became known as the 'photon' (i.e. discrete like a particle) and led to the paradox that light behaved both as a wave as well as a particle.
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Albert Einstein
• In 1921, Einstein was awarded the Nobel Prize for this discovery, though he never believed in light as particles.
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Robert Millikan 1909
Who? Robert Millikan
What? Calculated the charge and mass of an electron
How? Millikan’s Oil Drop Experiment and Thomson’s charge-to-mass ratio
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Results: Oil Drop Experiment
Millikan measured the charge of his oil droplets and found that they were all whole number multiples of the same minimum charge.
This minimum charge (1.6 x 10-19 coulombs) was the charge of the electron.
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Results: Oil Drop Experiment
• Using Thomson’s charge/mass ratio, Millikan also determined the mass of an electron
(9.1 x 10-28 g).
• Since atoms are neutral, they must contain a positive charge to balance the charge of the electron.
• Because electrons are so small in mass, atoms must contain additional particles that account for most of their mass.
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Ernest Rutherford 1911
Who? Ernest Rutherford
What? Discovered the nucleus
How? Gold Foil Experiment
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Ernest Rutherford
• Rutherford shot a stream of alpha particles (positively charged helium atoms) at a thin layer of gold foil expecting them to pass through undeflected as predicted by Thomson’s model.
• Most alpha particles did pass through undeflected, but some were partially deflected, and a very few (1 in 8,000) were greatly deflected nearly 180 degrees.
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Ernest Rutherford
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Ernest Rutherford’s Atomic Model
A very small densely packed nucleus containing all of the positive charge with electrons moving around the nucleus.
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Ernest Rutherford’s Atomic Model
Problems:• why electrons did not fall into the
nucleus as they moved around the atom as classical physics predicts.
• why only certain colors were produced by atoms when heated and cooled instead of all colors.
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Henry Moseley 1911
Who? Henry Moseley
What? Discovered that the positive charge of the nucleus increases by one unit from one element to the next.
How? By studying how light is diffracted in crystals, he found a systematic relationship between wavelength and atomic number.
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Henry Moseley
• Moseley proposes that the elements in the periodic table be arranged in order of increasing atomic number instead of atomic mass.
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Niels Bohr 1913 Who? Niels Bohr
What? Developed the planetary model of the atom.
How? Bohr made the connection between the wavelength of light an
element emits and its atomic structure. Bohr’s model was based upon the work done by Planck and Einstein and used it to modify Rutherford’s model.
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Niels Bohr
• “An expert is a man who has made all the mistakes which can be made, in a very narrow field.”
–Niels Bohr (1885-1962)
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Bohr’s Planetary Model
1) Electrons move around the atom’s nucleus in circular paths called orbits.
2) These orbits are definite distances from the nucleus and represent specific energy levels. Electrons can not exist in any position outside these designated energy levels (orbits) .
(1, 2, 3,.. or E1, E2, E3,.. or K, L, M, N,…)
3) Electrons orbiting closest to the nucleus have the lowest energy; those farthest from the nucleus have the highest energies. The lowest energy state is the ground state. A higher energy state is an excited state.
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Bohr’s Planetary Model
4) If electrons absorb energy, they move to higher energy levels (excited state).
When they drop back down to lower energy levels they release energy (as light). This energy (electromagnetic radiation) is seen as spectral lines and is given by: E = h, where: E = energy h = 6.6 x 10-34 J/hertz (Planck’s constant) = is the frequency of the radiation.
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Bohr’s Planetary Model
5) Energy is absorbed and given off in definite amounts called quanta which depends on the energy levels involved E = h where:
E = Ehigher(final) – Elower (initial) = h
• The energy “E” represents the energy of one photon (one quanta) of radiation (light).
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Bohr’s Planetary Model
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Bohr’s Planetary Model
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Summary of the Bohr Model
• Electrons travel in certain fixed orbits (each orbit having an associated energy) around the nucleus.
• Electrons are treated as particles and energy is quantized.
• An orbit is a place of fixed energy where an electron can be found, similar to the orbits of the planets around the sun.
• Bohr’s model of the atom worked well for the hydrogen but not for any other elements.
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Problems with Bohr’s Model
• The model is only valid for the hydrogen atom which has one electron.
• The assumption concerning stationary orbits violates the laws of classical mechanical physics.
• The assumption of quantized energy violates the Heisenberg uncertainty principle.
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Rutherford - 1919
Who? Rutherford
What? discovers the proton
How? Through his work with radioactivity
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Rutherford’s Atomic Model
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Louis de Broglie - 1924
Who? Louis de Broglie
What? Proposes the concept of the wave-particle duality of matter.
Matter (particles) can behave like a wave.
How? In his PhD thesis based on the work of Albert Einstein and Max Planck on light.
“Any moving particle or object has an associated wave.” 62
Louis de Broglie
• If waves (light) can have particle - like properties as proposed by Planck and Einstein, then matter can have wave like properties.
• De Broglie thus created a new field in physics, wave mechanics (quantum mechanics), uniting the physics of light and matter.
• De Broglie Wavelength: = h ∕ mv
• A 155 pound person running at 10 mph would have ≈ 2 x 10-33 m.
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Erwin Schrodinger - 1926
Who? Erwin Schrodinger
What? Developed his wave equations Viewed electrons as continuous clouds
How? Using de Broglie’s theory.
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Erwin Schrodinger
Treats the electron moving around the nucleus as wave. Applies to all atoms unlike Bohr’s model for hydrogen. Replaces two dimension orbits with three-dimensional orbitals.
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Quantum Mechanical Model Wave Mechanical Model Electron Cloud Model
• The electron is treated mathematically as a wave.
• The electron can be very close to the nucleus or very far away. However, the probability of the electron being a certain distance from the nucleus most of the time is high 90% (0.529 angstroms for the hydrogen 1s electron).
• Angstrom: A unit of length equal to 10-8 cm
(A = 10-8 cm) 66
Quantum Mechanical Model
• The energy is described in terms of the probability of locating the electron in a region of space outside the nucleus.
• Energy levels are not considered to be fixed orbits at specific distances from the nucleus. Instead, the energy levels are thought of as clouds surrounding the nucleus.
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Quantum Mechanical Model
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Electron Cloud Model
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Orbitals
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Werner Heisenberg - 1927
Who? Heisenberg
What? Heisenberg’s Uncertainty Principle: “it is not possible to know both the velocity and the position of a particle
at the same time.”
How? Theoretical physics and mathematical modeling of quantum mechanics.
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Heisenberg
The act of observing alters the reality being observed at least at the subatomic level.
To measure the properties of a particle such as an electron, you need to use a measuring device, usually light or radiation.
But, the energy in this radiation affects the particle being observed.
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James Chadwick 1931
Who? James Chadwick
What? Discovers the neutron, an elementary particle devoid of any electrical charge.
How? Working with Rutherford bombarding light elements with alpha particles (helium nuclei)
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James Chadwick
• Chadwick’s discovery paved the way towards the fission of uranium 235 and the creation of the atomic bomb.
From 1943 to 1946 he worked in the United States as Head of the British Mission attached to the Manhattan Project for the development of the atomic bomb.
• [Summary] Development of Atomic Theory
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Atomic Models
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Atomic Models
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Atomic Structure
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Atomic Structure
Atomic number (Z):• number of protons.
Also the number of electrons in a neutral atom. Z = 6
Mass number (A):• number of protons and
neutrons. A = 12
Average atomic mass:• the weighted average of
all the naturally occurring isotopes.
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Atomic Structure
Isotope: • atoms of the same element but having
different masses due to different numbers of neutrons.
Na-22; Na-23 Ga–69; Ga-71
Nuclides: • refers to the nucleus of an atom which
includes protons and neutrons.
Ion: • an atom or group of atoms that have a positive
or negative charge. 79
Atomic Structure
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Cations: • an atom or group of atoms having a positive
charge. Typically all metals form cations (Mg+2, Al+3, NH4
+). Anions: • an atom or group of atoms having a negative
charge. Typically all non-metals form anions (F-,SO4
2-). • The difference between the number of protons
and electrons in an atom determines the charge of its ion.
Average Atomic Mass Calculation
1) Hydrogen consists of three isotopes:
protium (H-1), deuterium (H-2 ), and tritium (H-3).
Calculate the average atomic mass of hydrogen if the relative abundance of H-1 is 99.2 %, H-2 is 0.8%, with only trace amounts of H-3.
1(.992) + 2(0.008) = 0.992 + 0.016 = 1.008 amu
• amu = atomic mass units = mass of one atom of hydrogen
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Average Atomic Mass Calculation
2) There are three isotopes of Carbon: C-12, C-13, and C-14 with relative abundances of 98.9%, 1.1% respectively, and only trace amounts of C-14. Calculate the average atomic mass of carbon.
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Average Atomic Mass Calculation
3) There are two isotopes of gallium. If the average atomic mass of gallium is 69.72 amu and the relative abundance of Ga-69 is 64%, calculate the mass number of the second isotope of Ga.
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Average Atomic Mass Calculation
4) There are two isotopes of lead. Pb-202 having a relative abundance of 24.6% and Pb-209. Calculate the average atomic mass of Pb.
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Atomic Particles Mass
Particle Charge Number amu
Electron (e-) -1 0 0.0005486
Proton (p+) +1 1 1.007276
Neutron (n) 0 1 1.008665
mass (g) Electron 9.11 x 10-28
Proton 1.673 x 10-24 Neutron 1.675 x 10-24
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Isotopes of HydrogenIsotope Protons Neutrons Abundance
Protium (H-1) 1 0 99.985%
Deuterium (H-2) 1 1 0.015%
Tritium (H-3) 1 2 Trace
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Isotopes of Hydrogen
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Protons, Neutrons, Electrons
1) How many protons and neutrons in Cd-110?
2) How many protons and electrons in Pt-200?
3) How many protons, neutrons, and electrons
in Sb+5-122?
4) How many protons, neutrons, and electrons
in P-3-34?
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Chemical Symbols, Formulas, and Equations
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Chemical Symbols, Formulas, and Equations Chemical Symbols:
The symbol for an element as represented in the periodic table.
Copper (Cu); Gold (Au); Hydrogen (H)
Chemical Formulas:
a shorthand notation for a substance (element, molecule, or compound) which indicates the type and number (subscript) of each element.
Hydrogen (H2); Water (H2O); Chlorine (Cl2);
Sulfuric acid (H2SO4); Glucose (C6H12O6);
Lead nitrate Pb(NO3)2 90
Chemical Equations
Chemical Equations: • indicate the types and numbers of elements,
molecules, and compounds taking part in a chemical reaction.
Reactants Products
2H2(g) + O2(g) 2H2O(g)
2Li(s) + F2(g) 2LiF(s)
2K(s) + 2H2O(l) H2(g) + 2KOH(aq)
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Chemical EquationsCoefficients:
represent the number of molecules, moles, or volume (gases only) of reactants and products.
2H2(g) + O2(g) 2H2O(g)
2 molecules H2 plus 1 molecule of O2 yields 2 molecules H2O
2 moles H2 plus 1 mole of O2 yields 2 moles H2O
2 liters H2 plus 1 liter of O2 yields 2 liters H2O
Mole ratio: the ratio of any substance to another in a chemical equation.
Ratio of O2:H2 = 1:2 Ratio of H2O:H2 = 1:1 9292
The Mole
The mole (symbol: mol) is an SI base unit and the measure of the amount of a substance (how many) not how much (mass).
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The Mole• The mole is defined as the number of particles
(atoms, molecules, ions, electrons, etc.) that are contained in 12 g of carbon-12. Therefore:
• one mole of iron contains the same number of atoms as one mole of gold.
• one mole of benzene contains the same number of molecules as one mole of water.
• the number of atoms in one mole of iron is equal to the number of molecules in one mole of water.
• one mole of desks is equal to one mole of grains of sand.
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• The mole is simply a shorthand way of referring to a large number.
602,000,000,000,000,000,000,000
6.02 x 1023
The mole is a convenient method used to count really, really small particles.
Avogadro’s Number
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How Big is a Mole?
• One mole of marbles, each 2 cm in diameter, would form a mountain 116 times higher than Mount Everest. The base of the marble mountain would be slightly larger than the area of the USA.
• One mole of marshmallows would cover the USA to a depth of 6500 miles.
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How Big is a Mole?
• If one mole of particles the size of sand grains were released by the eruption of Mount St. Helens, they would cover the entire state of Washington to the depth of a ten-story building.
• Avogadro's number (6.02 x 1023) is the approximate number of milliliters of water in the Pacific Ocean 7 x 1023 mL.
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How Big is a Mole?• Water flows over Niagara Falls at about
172,500,000 gallons per minute. At this rate it would take 134,000 years for one mole of water droplets (6.02 x 1023 drops) to flow over Niagara Falls.
• One mole of moles (animal), placed head to tail, would stretch 11 million light years and weigh 9/10 as much as the moon. Speed of light = 3.0 x 108 m/s. Mass of the moon = 6.7 x 1022 kg.
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How Big is a Mole?• One mole of unpopped popcorn kernels would
cover the entire United States to a depth of nine miles.
• One guacamole is the amount of taco chip dip that can be made from an Avogadro number of avocados, plus appropriate quantities of tomatoes, onions, and chili. A train stretching to the North Star and back 2-1/2 times would be required to transport one guacamole. NOTE: The North Star is 680 light years away. 99
Moles and Molar Masses
• Atomic Mass Unit (amu): a unit of mass equal to one-twelfth the mass of a carbon-12 atom.
• Gram atomic mass, formula mass, molecular weight, molecular mass, and molar mass are all terms normally used to describe the mass (in grams) of one mole of a substance (6.02 x 1023) atoms or molecules).
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Moles and Molar Masses
• The atomic mass of boron (B) is 10.811 amu (the mass of one boron atom).
• The actual mass of one atom of boron is 10.811 amu = 1.796 x 10-23 g.
6.02 x 1023
• The molar mass of boron (mass of one mole = 6.02 x 1023 atoms of boron) = 10.811 g.
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Moles and Molar Masses
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Calculating Molar Mass
• The molar mass of an element or a compound is the total mass of one mole of the element or compound.
• The molar mass is equal to the sum of the individual atomic masses of each atom in the molecule.
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Calculating Molar MassSteps to calculate molar mass:
1)Determine the formula if not given
2)Using the periodic table, determine the atomic mass of each element in the molecule or compound.
3)Multiply each element's atomic mass by the number of atoms of that element in the compound. The number of atoms is given by the subscript on the right next to the element symbol in the formula.
4)Add all of these masses together. The total will be the molar mass of the compound.
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Moles and Molar Masses
• The molar mass of sodium (Na) = 22.99 g.
• The molar mass of water (H2O) = 18.015 g
H: 2(1.008 g) = 2.016 g
O: 1(15.999 g) = 15.999 g
18.015 g/mol
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Calculation of Molar Mass
1) Calculate the molar mass of carbon tetrachloride CCl4.
2) Calculate the molar mass of boron triiodide BI3.
3) Calculate the molar mass of cesium carbonate Cs2CO3.
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[Stoichiometry]
Mole DiagramVolume A
M oles A
Atoms,M olecules,Particles A
M ass A
M ole Diagram
X
X
X
22 .4 L (22 .4 d m 3)
(a t STP)
÷
÷
6 .02 x 10 23
÷ M ola r M ass A
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Calculation of Molar Mass1) Determine the number of moles in 368 grams
of H2SO4.
368g = 98.09g/mole
2) Calculate the number of molecules in 63 g of nitric acid (HNO3).
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Calculation of Molar Mass
3) Calculate the volume of 22 g carbon dioxide (CO2).
4) Calculate the mass and volume of 3.75 mol CO2.
5) Calculate the mass of 18 L oxygen.
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Calculation of Molar Mass
6) Calculate the volume occupied by 3.75 g CO2.
A hydrate (with water) is a compound with water physically bound to it. The water can be removed by heating (anhydrous, without water).
To calculate the molar mass of a hydrate, add the total mass of the compound to the total mass of the water
Calculate the molar mass of BaSO4∙3H2O
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Calculation of Molar Mass
7) Calculate the molar mass, the number of moles, and the number of molecules in 62 g of the hydrate: LiNO3∙2H2O:
a)Molar mass =
b)# of mols =
c)# of molecules =
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Calculation of Molar Mass
8) Calculate the molar mass of the following hydrates:
MgSO4·2H2O
Fe(NO3)2·4H2O
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Calculation of Molar Mass
9) For the hydrate, MgSO4·2H2O:
How many oxygen atoms per molecule?
Total number of atoms per molecule?
Total number of moles of hydrogen per mole of compound?
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Calculation of Molar Mass
10) For the hydrate, Fe(HCO3)3·3H2O:
Total number of atoms per molecule of hydrate?
Total number of hydrogen atoms per molecule of hydrate?
Total number of oxygen atoms per molecule of hydrate?
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Calculation of Molar Mass
11) For the hydrate, Fe(HCO3)3·3H2O:
Calculate the total number of hydrogen atoms per mole of hydrate?
The total number of atoms per mole of hydrate?
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Calculations
Calculate:
1. The number of moles in 150 g sulfur.
2. The mass of 4.214 x 1023 atoms of lead.
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Calculations
3. What is the volume occupied by 1.08 x 104 g Rn at STP?
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Calculations
4. What equivalent mass of xenon is equal to 2.408 x 1015 atoms of Cr?
• [atoms Cr → mol Cr = mol Xe → mass Xe]
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Calculations
5) If you have 186 g sodium, calculate the equivalent mass of barium.
6) In the reaction between copper and selenium, 25.4 g of copper will react with what equivalent mass of selenium? How much CuSe will be produced? Cu + Se → CuSe
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Calculations
7) Iron has a density of 9.8 g/cm3. Calculate the number of atoms of iron in 144 cm3.
[density Fe → mass Fe → mol Fe → atoms Fe] D = m/V m = DV
120
Calculations
8) The density of lead is 11.35 g/cm3.
Calculate the number of moles and atoms contained in 3.6 cm3.
D = m/V
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Calculations
9) 20 g of HCl is equal to what equivalent mass of NaOH?
10) 40 g CuSO4 is equal to what equivalent mass of Pb3(PO4)4?
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Calculations
11) Calculate the heat of fusion in joules/gram if 52 g of an unknown metal melts after absorbing 6240 joules of heat.
12) If the molar mass of the metal above is 198.6 g/mol, calculate the molar heat of fusion in kJ/mol.
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Calculations
13) A substance has a molar mass of 226 g/mol. If 42 g of this substance absorbs 5.206 kJ when it melts, calculate:
The number of moles in the sample
The molar heat of fusion in J/mol
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Calculations14) In the reaction:
Ca + Se → CaSe, 4.2 g Ca will react with what equivalent mass of Se?
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