atoms all matter is made of them

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Atoms are very small, and they are made up of even smaller subatomic particles.


  • AtomsAll matter is made of themIdea came from Greek philosopher Democritus400 B.CGreek word atomos not to be cutDid not use scientific methodNo experiments to support idea

  • Atoms are very small, and they are made up of even smaller subatomic particles.

  • Parts of AtomsAtoms can be broken.There are many different particlesWe will learn about the three most important to chemistryProton positively charged, big massElectron negatively charged, very small massNeutron no charge, about the same mass as a proton

  • Parts of AtomsProton and neutron are about 2000 times heavier than the electronProtons and neutrons are located in the nucleusElectrons outside the nucleusAn atom is mostly emptyIf the atom were the size of a baseball stadium, the nucleus would be the size of a marble

  • What is the difference between protons, neutrons, and electrons?

    The three main subatomic particles are distinguished by mass, charge, and location in the atom.

  • Draw Diagram

  • Each element has a unique number of protons.

    Unreacted atoms have no overall charge.Because there is an equal number of protons and electrons, the charges cancel out.

    The electric force holds the atom together.Positive protons are attracted to negative electrons by the electric force. This force holds the atom together.

  • Counting the piecesAtomic Number- the number of protonsDetermines the type of atom and elementMass number- number of protons and neutronsAll the heavy piecesElectrons are the same as protons if neutral.If an ion, it gained or lost electrons

  • The Mass of AtomsVery, very smallCant use gramsUse the Atomic Mass Unit (amu)One twelfth the mass of a carbon-12 atomSince carbon-12 has 6 protons and 6 neutrons makes the mass of a proton or neutron 1.0 amu

  • Atomic MassMass of the average atomSince there are isotopes of atoms two things affect the averageThe mass of the isotopesHow much of each isotope there isThese are the decimal numbers on the periodic table

  • Atomic Number and Mass NumberWhat do atoms of an element have in common with other atoms of the same element?

    Atoms of each element have the same number of protons, but they can have different numbers of neutrons.

  • The atomic number equals the number of protons.

    atomic number: the number of protons in the nucleus of an atom

    The mass number equals the total number of subatomic particles in the nucleus.

    mass number: the sum of the numbers of protons and neutrons in the nucleus of an atom

  • Atomic MassesWhat unit is used to express atomic mass?

    Because working with such tiny masses is difficult, atomic masses are usually expressed in unified atomic mass units.

    unified atomic mass unit: a unit of mass that describes the mass of an atom or molecule; it is exactly 1/12 the mass of a carbon atom with mass number 12 (symbol, u)

  • Average atomic mass is a weighted average.Isotope abundance determines the average atomic mass.Example: Chlorine-35 is more abundant than chlorine-37, so chlorines average atomic mass (35.453 u) is closer to 35 than to 37.

  • Atomic MassTwo isotopes of copper 72% copper-6328% copper-65Makes the average 63.56 amu

  • IsotopesAtoms of the same type can have different numbers of neutronsThese are isotopesThey behave identicallyThey just weigh different amountsMass number is written after the nameHydrogen 1Hydrogen 2

  • Atomic Number and Mass Number, continued

  • IsotopesWhy do isotopes of the same element have different atomic masses?

    Isotopes of an element vary in mass because their numbers of neutrons differ.

  • Isotopes, continued

  • Some isotopes are more common than others.radioisotopes: unstable isotopes that emit radiation and decay into other isotopes

    The number of neutrons can be calculated.number of neutrons = mass number atomic number

  • The mole is useful for counting small particles.

    mole: the SI base unit used to measure the amount of a substance whose number of particles is the same as the number of atoms of carbon in exactly 12 g of carbon-12 (abbreviation, mol)

    1 mol = 602, 213, 670, 000, 000, 000, 000, 000 particles

    This number, usually written as 6.022 1023, is called Avogadros number.

  • Moles and grams are related.

    molar mass = the mass in grams of one mole of a substanceExample: 1 mol of carbon-12 atoms has a mass of 12.00 g, so the molar mass of carbon-12 is 12.00 g/mol

    You can convert between moles and grams.

  • Math SkillsConverting Moles to GramsDetermine the mass in grams of 5.50 mol of iron.

    1. List the given and unknown values.

    Given: amount of iron = 5.50 mol Femolar mass of iron = 55.84 g/mol Fe*Unknown:mass of iron = ? g Fe

    *Use the periodic table to find molar masses. The average atomic mass of an element is equal to the molar mass of the element. This book rounds values to the hundredths place.

  • Math Skills, continued2. Write down the conversion factor that converts moles to grams.The conversion factor you choose should have what you are trying to find (grams of Fe) in the numerator and what you want to cancel (moles of Fe) in the denominator.

    3. Multiply the amount of iron by this conversion factor, and solve.

  • Compounds also have molar masses.

    To find the molar mass of a compound, add up the molar masses of all of the atoms in a molecule of the compound.

    Example: finding the molar mass of water, H2Omolar mass of O = 16.00 g/molmolar mass of H = 1.01 g/mol molar mass of H2O = (2 1.01 g/mol) + 16.00 g/mol = 18.02 g/mol

  • Energy LevelDescribe the path the electron takes around the nucleusFarther from nucleus is more energyGain energy they move awayLose energy they move towardOnly certain energies are allowed in each atom

  • Energy LevelsLike an elevatorit can only be on certain floorsNever in betweenEnergy levels get closer together the higher you goEach has room for a certain number of electrons

  • Current ModelTreats electrons as waves, not particlesTalks only about the probability of finding an electronRegion called the electron cloudWhere are the blades in a fan?It is impossible to know the exact location and the speed and direction of an electron

  • OrbitalsRegions where you have a chance of finding the electronThere are different types of orbitalss, p, d, fEach has its own shape or shapesEach shape has room for two electronsEach can be found in the energy levels

  • S orbitalShaped like a sphereRoom for 2 electrons

  • P orbitals3 dumbbell-shaped regionsOne on each axes of a 3-D graph

  • P orbitalsEach shape can hold two electronsTotal of 6

  • d orbitalsFive different shapesMore complexEach can hold 2 electronsTotal of 10 electrons

  • d orbitals

  • f orbitalsseven different shapesMuch more complexEach can hold 2 electronsTotal of 14 electrons

  • f orbitals

  • Valence electronsThe electrons in the outermost energy levelResponsible for most of the chemical propertiesWhen two atoms interact, the outside electrons are the ones affected

  • Elements and the Periodic Table

  • Where did the elements come from?


  • AlchemyWhat was the main objective of early alchemists?To make gold from lead.

    Why was this impossible?Add 18 protons to nucleus, present technology is only 1 and only under extreme circumstances.


  • What are synthetic elements?Elements created in the lab. Usually unstable and may be radioactive.

    How many elements are naturally occurring?93

    Where are elements created?In the center of stars.


  • What is a nuclear reaction?A reaction that changes the composition of the nucleus of an atom.


  • What is a transmutation?Changing one nucleus into another by either radioactive disintegration or bombardment of the nucleus with other particles.


  • What is a cyclotron?A device that accelerates charges particles to high energy states. Then they are collided with atomic nuclei forming atoms of a higher atomic number.


  • What is a synchrotron?A device that times the impulses of energy in a cyclotron to match the acceleration of the particle. The particles collide forming super heavy elements.

    What are super heavy elements?An element with an atomic number greater that 103.


  • The Periodic TableListed in order of increasing number of protonsWhen you do this the properties of the elements repeat.Periodic Law- when the elements are arranged in order of increasing number of protons, the properties tend to repeat in a pattern

  • What makes a group of elements?


  • What do you know about the periodic table?

    Arranged by atomic #

    Gives average atomic mass


  • How are elements different?Solids, liquids and gases.Colors

    How are elements alike?Chemical properties


  • Modern Periodic TableWhat was known in the mid 1800s?Elements had atomic massesSome elements had similar physical and chemical properties.John Newlands noticed that when the 16 known elements were placed in order of atomic mass that the elements in the same column had similar properties.


  • Dimitri Mendeleev: 187063 known elements.Used Newlands method to arrange elements according to atomic mass and properties.

    The table had gaps and some of the atomic masses were reversed.

    The gaps were undiscovered elements.


  • OrganizationElements are organized based onChemical PropertiesValence Number (the

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