chapter 3 - atoms: the building blocks of matter

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Chapter 3 - Atoms: the building blocks of matter Taken from Modern Chemistry written by Davis, Metcalfe, Williams & Castka

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Chapter 3 - Atoms: the building blocks of matter. Taken from Modern Chemistry written by Davis, Metcalfe, Williams & Castka. HW – Notes on section 3.1 pgs 65-67. Section 3.1 – The Atom: from philosophical idea to scientific theory. Students will be able to : Explain the laws of - PowerPoint PPT Presentation

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Page 1: Chapter 3 - Atoms: the building blocks of matter

Chapter 3 - Atoms: the building blocks of matter

Taken from Modern Chemistry written by Davis, Metcalfe, Williams

& Castka

Page 2: Chapter 3 - Atoms: the building blocks of matter

Section 3.1 – The Atom: from philosophical idea to scientific theory

Objectives

Students will be able to :• Explain the laws of

Conservation of massDefinite proportionMultiple proportion

• Summarize the 5 essential points of Dalton’s atomic theory

• Explain the relationship between the 5 essential points and the above mentioned laws

HW – Notes on section 3.1 pgs 65-67

Page 3: Chapter 3 - Atoms: the building blocks of matter

Section 3.1 – The Atom: from philosophical idea to scientific theory

Foundations of Atomic Theory

As early as 400 B.C.E. particle theory of matter was supported – the particle was called an atom based on the Greek for “indivisible”.

Supported by DemocritusAristotle did not believe this theory

and his opinion lasted for 2 000 years. Felt all matter was continuous.

Page 4: Chapter 3 - Atoms: the building blocks of matter

Section 3.1 – The Atom: from philosophical idea to scientific theory

Foundations of Atomic Theory (continued)

By 1700s accepted idea that an element could not be broken down further. Back

The transformation of substance or substances into one or more new substances was known as a chemical reaction.

By the 1790s there was a new emphasis on quantitative analysis of chemical reactions

Page 5: Chapter 3 - Atoms: the building blocks of matter

Section 3.1 – The Atom: from philosophical idea to scientific theory

Foundations of Atomic Theory (continued)

This work lead to the discovery of several laws. . .

Law of Conservation of matter which states that mass is neither destroyed or created during ordinary chemical or physical reactions.

Antoine LavoisierBack

Page 6: Chapter 3 - Atoms: the building blocks of matter

Section 3.1 – The Atom: from philosophical idea to scientific theory

Foundations of Atomic Theory (continued)

The law of definite proportions, sometimes called Proust's Law, states that a chemical compound always contains exactly the same proportion of elements by mass.

Book example: salt is always 39.34% Na (sodium) and 60.66% Cl (Chlorine) by mass

Joseph Proust

Page 7: Chapter 3 - Atoms: the building blocks of matter

Section 3.1 – The Atom: from philosophical idea to scientific theory

Foundations of Atomic Theory (continued)

The law of multiple proportions, statement that when two elements combine with each other to form more than one compound, the weights of one element that combine with a fixed weight of the other are in a ratio of small whole numbers.

You Tube Help

Back

Rethink value of video

Page 8: Chapter 3 - Atoms: the building blocks of matter

Section 3.1 – The Atom: from philosophical idea to scientific theory

Dalton’s Atomic Theory1.All matter is made of extremely small particles called atoms. Relationship

2.All atoms of the same element are identical in size, mass & other properties. Relationship

3.Atoms cannot be subdivided, created or destroyed. Relationship

4.Atoms of different elements combine in WHOLE-number ratios to form compounds.

5.In chemical reactions atoms are combined, separated or rearranged. Relationship

Page 9: Chapter 3 - Atoms: the building blocks of matter

Section 3.1 – The Atom: from philosophical idea to scientific theory

Modern Atomic TheoryDalton turned idea’s (of ancient Greeks) into scientific theory

Today we know that atoms can be divided, but the law of conservation of matter holds true still.

Page 10: Chapter 3 - Atoms: the building blocks of matter

Section 3.1 – The Atom: from philosophical idea to scientific theory

Quiz Break

Page 11: Chapter 3 - Atoms: the building blocks of matter

Section 3.2 – The Structure of the Atom

Objectives

Students will be able to :• Summarize the observed properties of cathode rays that led to the discovery of the electron.• Summarize the experiment carried out by Rutherford and his co-workers that led to the discovery of the nucleus.• List the properties of protons, neutron and electrons•Define atom.

HW – Notes on section 3.2 pgs 70-74

Page 12: Chapter 3 - Atoms: the building blocks of matter

Section 3.2 – The Structure of the Atom

Discovery of the Electron

1st discovery of a subatomic particle resulted from investigations into the relationship between electricity and matter.

Page 13: Chapter 3 - Atoms: the building blocks of matter

Section 3.2 – The Structure of the AtomDiscovery of the Electron - Cathode Rays and Electrons

Hypothesized that the glow was caused by a stream of particles which they called a cathode ray.

Tested and found that1.An object placed between the cathode ray and the opposite end casts a shadow.2.A paddle wheel placed on rail

s rolled toward the anode from the cathode

.

Page 14: Chapter 3 - Atoms: the building blocks of matter

Section 3.2 – The Structure of the AtomDiscovery of the Electron - Cathode Rays and Electrons (continued) This supported the idea of a cathode ray. . .

Further testing found that1.Cathode rays were deflected by a magnetic field.2.Deflected away from negatively charged objects.

Thompson hypothesized that the ray was a particle, a negative one – later named electrons.

Page 15: Chapter 3 - Atoms: the building blocks of matter

Section 3.2 – The Structure of the AtomCharge and Mass of the electrons Thompson’s work showed that the electron has a very large charge for its tiny mass

R. A. Millikan (right) showed the mass to be

9.109 x 10-31 kg

Page 16: Chapter 3 - Atoms: the building blocks of matter

Section 3.2 – The Structure of the AtomCharge and Mass of the electrons – (continued) Based on that information two more inferences were made about atomic structure.

1.Atoms are electrically neutral so there must be positively charged particles to balance out the negative electron.

2.Because electrons have so much less mass than atoms, atoms must contain other particles which account for most of their mass.

Page 17: Chapter 3 - Atoms: the building blocks of matter

Section 3.2 – The Structure of the Atom

Discovery of the Atomic Nucleus

Ernest Rutherford & associates bombarded a thin gold foil with alpha particles (+ charge & 4 x mass of H atom)

Expected most particles to pass through with slight deflection – shocked to find that 1 in 8 000 were redirected back toward source.

Page 18: Chapter 3 - Atoms: the building blocks of matter

Section 3.2 – The Structure of the Atom

Discovery of the Atomic Nucleus – (continued)

Rutherford reasoned that the bounce back was from a densely packed bundle with a positively bundle he called the nucleus.

If the nucleus were the size of a marble the atom would be the size of a football field

Page 19: Chapter 3 - Atoms: the building blocks of matter

Section 3.2 – The Structure of the Atom

Composition of the Atomic Nucleus

Except for the simplest type of hydrogen all atomic nuclei are made of two types of particles, protonsprotons and neutronsneutrons.

Protons have a (+) charge which balances out the charge of the electrons.

Mass = 1.673 x 10-27 kg

Neutrons have a no charge and amass = 1.675 x 10-27 kg

Page 20: Chapter 3 - Atoms: the building blocks of matter

Section 3.2 – The Structure of the Atom

Composition of the Atomic Nucleus – (continued)

Nuclei of atoms of different elements differ in the # of protonsprotons they contain and therefore in the amount of positive charge.

Page 21: Chapter 3 - Atoms: the building blocks of matter

Section 3.2 – The Structure of the Atom

Properties Summarized

Particle SymbolsRelative electric charge

Mass number

Relative Mass (amu*)

Actual mass (kg)

Electron e-, -1 0 0.000 5486 9.109 x 10-31

Proton p+, +1 1 1.007 276 1.673 x 10-27

Neutron no, 0 1 1.008 665 1.675 x 10-27

e0-1

1 0

n

1 1

H

* 1 amu (atomic mass unit) = 1.660 540 x 10-27 kg

Page 22: Chapter 3 - Atoms: the building blocks of matter

Section 3.2 – The Structure of the AtomComposition of the Atomic Nucleus - Forces in the Nucleus

Like forces generally repel one another however when two protons are extremely close there is a strong attractions

These short-range proton-neutron, proton-proton, and neutron-neutron forces hold the particles together and a referred to as nuclear forces.nuclear forces.

Page 23: Chapter 3 - Atoms: the building blocks of matter

Section 3.2 – The Structure of the Atom

The sizes of Atoms

Atomic radii range from 40 to 270 pm (picometers)

Where as the nuclei of atoms have a much smaller radiiAbout 0.001 pm

Page 24: Chapter 3 - Atoms: the building blocks of matter

Section 3.3(A) – Counting Atoms

Objectives

Students will be able to :• Explain what isotopes are.• Define atomic number and mass number, and describe how they apply to isotopes.• Given the identity nuclide, determine its number of protons, neutrons and electrons.

HW – Notes on section 3.3 pgs 75-80

Page 25: Chapter 3 - Atoms: the building blocks of matter

Section 3.3(A) – Counting AtomsAtomic NumberThe atomic numberatomic number of an element is the number of protons in the nucleus of each atom of that element

Page 26: Chapter 3 - Atoms: the building blocks of matter

Section 3.3(A) – Counting Atoms

IsotopesIsotopes Isotopes are atoms of the same element that have different masses.

All hydrogen contain the same number of protons but may contain different number of neutrons.

Page 27: Chapter 3 - Atoms: the building blocks of matter

Section 3.3(A) – Counting Atoms

Mass Number

The mass number mass number is the total number of protons and neutrons in the nucleus of an isotope.

Mass Number 1 2 3

Page 28: Chapter 3 - Atoms: the building blocks of matter

Section 3.3(A) – Counting Atoms

Isotopes - pogil

Page 29: Chapter 3 - Atoms: the building blocks of matter

Section 3.3(A) – Counting Atoms

Isotopes – Pennium Lab

Page 30: Chapter 3 - Atoms: the building blocks of matter

Section 3.3(A) – Counting Atoms

Designating IsotopesNuclide Nuclide is a general term for any isotope of any element.

Nuclear Symbol

Sab

S = element’s symbola = protons + neutronsb = protons

3580

BrBromine has

Protons = ______

Neutrons = _______

Electrons = ________ Practice Practice Key

Page 31: Chapter 3 - Atoms: the building blocks of matter

Section 3.3(A) – Counting Atoms

Relative Atomic MassesThe standard used by scientist to govern units of atomic mass is the carbon-12 nuclide. One atomic mass atomic mass unit unit , or amu is exactly 1/12th the mass of a carbon-12 atom, or 1.660 540 x 10-27 kg

Although isotopes may have different masses, they do not differ significantly in their chemical behavior.

Page 32: Chapter 3 - Atoms: the building blocks of matter

Section 3.3(A) – Counting Atoms

Average Atomic Masses of Elements

AverageAverage atomic mass atomic mass is the weighted average of the atomic masses of the naturally occurring elements.

Example with marbles (100 total)

25 marbles x 2.00 g = 50 g75 marbles x 3.00 g = 225 g

Adding the masses gives

50 g + 225 g = 275 g

Divide this by the total number of marbles and you get an average marble mass of 2.75 g

Page 33: Chapter 3 - Atoms: the building blocks of matter

Section 3.3(A) – Counting AtomsAverage Atomic Masses of Elements –(continued)

AverageAverage atomic massatomic massHow are the masses on the periodic table determined?How are the masses on the periodic table determined?

(KEY)

Page 34: Chapter 3 - Atoms: the building blocks of matter

Section 3.3(B) – Counting Atoms

Objectives

Students will be able to :•Define mole in terms of Avogadro’s number, and define molar mass.•Solve problems involving mass in grams, amount in moles and number of atoms of an element.

HW – Notes on section 3.3 pgs 80-85

Page 35: Chapter 3 - Atoms: the building blocks of matter

Section 3.3(B) – Counting AtomsRelating Mass to Numbers of Atoms - the Mole

A mole mole (abbreviated mol)is the amount of a substance that contains as many particles as there are atoms in exactly 12 g of carbon-12.

Page 36: Chapter 3 - Atoms: the building blocks of matter

Section 3.3(B) – Counting AtomsRelating Mass to Numbers of Atoms – Avogadro’s number

The number of particles in a mole has been experimentally determined in a number of ways.

Avogadro’s number Avogadro’s number 6.011 1367 x 1023 – is the number of particles in exactly one mole of a pure substance.

For ours (and most purposes) Avogadro’s number is rounded to 6.022 x 1023

Page 37: Chapter 3 - Atoms: the building blocks of matter

Section 3.3(B) – Counting AtomsRelating Mass to Numbers of Atoms – Molar Mass

The alternative definition of mole is the amount of substance that contains avogadro’s number of particles.

The mass of one mole of a pure substance is called the molar mass molar mass of that substance. Usually written in units of g/mol.

Page 38: Chapter 3 - Atoms: the building blocks of matter

Section 3.3(B) – Counting AtomsRelating Mass to Numbers of Atoms – Gram/Mole Conversions

There are 3 mole equalities. They are:

1 mol = 6.02 x 1023 particles1 mol = g-formula-mass

(periodic table)1 mol = 22.4 L for a gas at

STP*

* STP = 0° C & 1 atm Pressure

Page 39: Chapter 3 - Atoms: the building blocks of matter

Section 3.3(B) – Counting AtomsRelating Mass to Numbers of Atoms – Conversions

There are 3 mole equalities. They are:

1 mol = 6.02 x 1023 particles1 mol = g-formula-mass (periodic table)

1 mol = 22.4 L for a gas at STP*

These become. . .

[-------------] or [-------------] 1 mol

6.02 x 1023 particles 1 mol 6.02 x 1023 particles

[-------------] or [-------------] 1 mol g-formula-mass (periodic table) 1 mol

g-formula-mass (periodic table)

[----] OR [----] 1 mol 22.4 L 1 mol

22.4 L

Page 40: Chapter 3 - Atoms: the building blocks of matter

Reference Sheet

There are 3 mole equalities. They are:

1 mol = 6.02 x 1023 particles1 mol = g-formula-mass (periodic table)

1 mol = 22.4 L for a gas at STP*

These become. . .

[-------------] or [-------------] 1 mol

6.02 x 1023 particles 1 mol 6.02 x 1023 particles

[-------------] or [-------------] 1 mol g-formula-mass (periodic table) 1 mol

g-formula-mass (periodic table)

[----] OR [----] 1 mol 22.4 L 1 mol

22.4 L

Page 41: Chapter 3 - Atoms: the building blocks of matter

Section 3.3(A) – Counting AtomsRelating Mass to Numbers of Atoms – What does it mean?

g-formula-mass (periodic table)

For a single element it is simply the atomic mass found on the periodic chart

Page 42: Chapter 3 - Atoms: the building blocks of matter

Section 3.3(A) – Counting AtomsRelating Mass to Numbers of Atoms – Examples

g-formula-mass (periodic table)

N

Ca

Ag

Ba

Page 43: Chapter 3 - Atoms: the building blocks of matter

Section 3.3(A) – Counting AtomsRelating Mass to Numbers of Atoms – What does it mean?

g-formula-mass (periodic table)

For a COMPOUNDCOMPOUND you will need to calculate using atomic mass found on the periodic chart

Page 44: Chapter 3 - Atoms: the building blocks of matter

Section 3.3(B) – Counting AtomsRelating Mass to Numbers of Atoms – EXAMPLE

g-formula-mass (periodic table)

COMPOUNDSCOMPOUNDS

Table Salt

NaCl

Water

H2O

Sugar(glucose)

C6H12O6

Page 45: Chapter 3 - Atoms: the building blocks of matter

Section 3.3(B) – Counting AtomsRelating Mass to Numbers of Atoms – EXAMPLE

g-formula-mass (periodic table)COMPOUNDSCOMPOUNDS

inorganic salt(soil fertilizer)

(NH4)2SO4

Page 46: Chapter 3 - Atoms: the building blocks of matter

Section 3.3(B) – Counting AtomsRelating Mass to Numbers of Atoms – MOLE PRACTICES

Practice 1

Practice 2 Practice 2 (Key)

Page 47: Chapter 3 - Atoms: the building blocks of matter

Section 3.3(B) – Counting AtomsRelating Mass to Numbers of Atoms – FUN WITH MOLES

Given : 2.860 m ceiling height9.630 m room depth10.620 m room width

Atmosphere composition:

Nitrogen - 78.084%Oxygen - 20.95%

1 000 L = 1 m3

How many mols of O2 and N2 are present in this room?

Page 48: Chapter 3 - Atoms: the building blocks of matter

Section 3.3(B) – Counting AtomsRelating Mass to Numbers of Atoms – FUN WITH MOLES

Atmosphere composition:

Nitrogen - 78.084%Oxygen - 20.95%

How many particles of O2 and N2 are taken in with each breath?

Average lung volumes in healthy adults[7]

VolumeValue (litres)

In men In womenInspiratory

reserve volume 3.3 1.9

Tidal volume 0.5 0.5Expiratory

reserve volume 1.0 0.7

Residual volume 1.2 1.1

Page 49: Chapter 3 - Atoms: the building blocks of matter

Section 3.3(B) – Counting AtomsRelating Mass to Numbers of Atoms – suggestions

1. Relax 2. Look for things you recognize3. Estimate size of final answer

(with this comes do I remember using any of these before)4. Set up and work out5. Double check with estimate and

your sig figs

Page 50: Chapter 3 - Atoms: the building blocks of matter

Section 3.3(B) – Counting AtomsRelating Mass to Numbers of Atoms – MORE MOLE PRACTICES

Practice 3 Practice 3 (KEY)

TAKE-HOME QUIZ (KEY)

TAKE-HOME QUIZ

Practice 4 Practice 4 (KEY)

Page 51: Chapter 3 - Atoms: the building blocks of matter

Section 3.3(B) – Counting AtomsRelating Mass to Numbers of Atoms – Q - #4

100 atoms Ar 1 x 102 atoms Ar

1 x 102 atoms Ar-------------------------

1X -------------------------

Want to get to Mols...

6.02 x 1023 particles

1 mol

0.166 x 10-21 particles , which is equal to 1.66 x 10-1 x 10-21

Or more properly written as 1.66 x 10-22 mols Ar