Chemistry Regents Chemistry Regents ReviewReview

The AtomThe Atom

• Describe the atom.

• How do we “write” an atom?

Some experiments of note:Some experiments of note:

• Greeks view of nature

• J.J. Thompson’s cathode ray

• Ernest Rutherford’s gold foil experiment

• John Dalton’s Atomic Theory

Modern Atomic Theory:Modern Atomic Theory:

1. The Bohr Model of the Atoma) “Planetary” model (K,L,M,N,O,P, and Q or

1-7)

2. The Wave-Mechanical Modela) Electrons move within an orbital

b) An orbital is a region where an electron is most likely to be found.

c) Energy.

Subatomic ParticlesSubatomic Particles

1. Protons and Neutrons -24

a) 1.67 x 10 g = about 1 amu

2. Electrons

a) 1/1800 of an amu

Atomic Mass, Atomic Number, and Atomic Mass, Atomic Number, and Isotopes:Isotopes:

• Atomic mass is the number of neutrons plus the number of protons.

• Atomic number is the number of protons. This can never change for a particular element. What does that mean?

• An Isotope of an element will have different number of neutrons.

More electron stuff:More electron stuff:

• Where are electrons located?

• What are energy levels, and how do electrons move between them?

Ground vs ExcitedGround vs Excited

1. Ground state for sodium:1. Na 2-8-1

2. Excited State for sodium:1. Na 2-7-2

Bright-line spectra for some elements:Bright-line spectra for some elements:

Electon Arrangement:Electon Arrangement:

• The four Quantum Numbers describe the location of an individual electron. Think address!

• No two electrons can have the same four quantum numbers.

Electron ConfigurationElectron Configuration

• According to the Periodic Table

• If you can make a connection with the quantum numbers, electron configuration, and the Periodic Table, then you’ve got it made kid! Let’s try!

Types of MatterTypes of Matter

• Homogeneous – Uniform composition throughout.– Ex/ elements, compounds, and apple juice,.

• Heterogeneous– Different composition throughout.– Ex/ chocolate chip cookie, and rocks in water.

Pure substance vs. MixturesPure substance vs. Mixtures

• Pure substances include elements and compounds. Define them.

• Mixtures can be homogeneous or heterogeneous, are made up of two or more pure substances and can be separated by physical means. What does this mean?

Chemical SymbolsChemical Symbols

• What is a chemical symbol?

• What is it’s purpose?

• Draw the chemical symbol for your favorite element.

Diatomic MoleculesDiatomic Molecules

• Some elements exist in nature as two covalently bonded atoms.

• Make sure you always write with a subscript of 2.

• They are: O2, H2, N2, F2, Cl2, Br2, and I2.

Chemical FormulasChemical Formulas

1. Qualitative information.1. Symbols.

2. Quantitative information.1. Numbers.

More Formulas:More Formulas:

• Empirical Formula• Lowest whole number ratio. Ex/ HO is the

empirical formula for hydrogen peroxide.

• Molecular Formula• Actual chemical formula. Ex/ H2O2 is the molecular

formula for hydrogen peroxide.

Ionic ChargesIonic Charges

• Atoms and compounds are electrically neutral, but ions are not.

• A polyatomic ion is a group of atoms covalently bonded and possessing a charge.

• Many compounds form from oppositely charged ions attracting each other.

Writing Formulas and Naming Writing Formulas and Naming Compounds:Compounds:

• Stoichiometric Coefficients tell us how many there are of a certain molecule or substance. Ex/ 2H2O tells us that there are two molecules of water.

• Equalizing charges allows us to write the chemical formula of a molecule with the appropriate ratio of atoms/molecule. Ex/ Na+ and Cl- combine in a one to one ratio to make NaCl.

Naming CompoundsNaming Compounds

• Binary Ionic compounds:• Positive ion first, negative ion second with “ide”

ending. Ex/ sodium chloride.

• Binary Covalent compounds:• Metal first, then non-metal. Or, if two non-metals,

element with lower electronegativity goes first. Prefixes apply with “ide” ending. Ex/ carbon dioxide.

• The Stock System: • Metals with more than one oxidation state. Ex/

Fe2+ combined with oxygen is Iron (II) oxide.

Chemical Reactions and Equations:Chemical Reactions and Equations:

• Physical Changes-– Often phase changes. No new substance is

formed. Ex/ ice melting.

• Chemical Changes-– Represented by chemical equations.

Reactants and products formed. Ex/ combustion of gasoline. A chemical reaction.

Chemical Equations:Chemical Equations:

Types of Chemical Rxs Types of Chemical Rxs video:video:

http://www.youtube.com/watch?v=http://www.youtube.com/watch?v=tE4668aarcktE4668aarck

Heat ReactionsHeat Reactions

• Endothermic – Surrounding temperature decreases, PE of

products increases, and ΔH is positive. Ex/H2O(s) + energy → H2O(l)

• Exothermic– Surrounding temperature increases, PE of

products decreases, and ΔH is negative. Ex/Ch4 + 3O2 → CO2 + 2H2O + energy

Balancing Chemical EquationsBalancing Chemical Equations

• The Law of Conservation of Mass:– Says we need equal amounts on both product

and reactant side of a chemical equation.– We can determine an unknown within a

chemical formula based on this law.

• Example: – 2H2(g) + O2 → 2H2O(g)

Balancing Chemical Balancing Chemical Equations video:Equations video:

http://www.youtube.com/watch?v=RnGuhttp://www.youtube.com/watch?v=RnGu3xO2h74&NR=1&feature=fvwp3xO2h74&NR=1&feature=fvwp