• Find image for trends of ionic charges.

Early Atomic Experiments

Plum Pudding Model

A large cloud of positive charge with small chocolate chips of negative charges.

Used cathode ray tube to tell us that atoms have negative charges.

Rutherford's Gold Foil Accepted Atomic Model

Most particles moved through gold foil.

• Some reflected, fewer bounced back.

Told us that atoms are largely empty space with small, dense center of positive charge.

Subatomic Model

• Most mass in center of atom, consisting of protons and neutrons.
• Has a larger electron cloud with negative electrons, mostly empty space.

Nucleus

Dense center consisting of protons and neutrons.

Protons

Exists in the nucleus.

Mass = 1.673E-27kg

p+ = +1 charge, positive charge, 1.602E-19 C.

Equal but opposite charge of electron.

Neutrons

No charge

Helps protons pack tightly together w/o repelling.

Slightly heavier mass than protons.

N0 = 0 charge

Atomic Number

Number of protons in an atom.

The atomic number is unique to an element.

Changing electrons or neutrons give us ions and isotopes, respectively.

Mass Number (A) Atomic Mass

Number at the bottom of the periodic table.

$$A \frac{g}{mol} = \text{protons} + \text{neutrons}$$

Isotopes

Different number of neutrons.

Can write mass number before element symbol like ^(10)B and ^(11)B for different isotopes of Boron.

• Boron always has 5 protons, may have 5 or 6 neutrons.

• Isotopes can be written out - Boron-12 or Boron-11

Molar mass is the weighted average of different abundances of isotopes. Molar mass = (abundance of isotope A in decimal)(molar mass of isotope A) + (abundance of isotope B in decimal)(molar mass of isotope B)

Electrons

e- = -1 charge

Electrons don't affect the molar mass because they are 1800 times smaller than a proton.

Changing the number of electrons gives us ions.

Removing electrons = positive ion = cation = Mg2+

Adding electrons = negative ion = anion = F-

Combustion Analysis

• Allows us to determine the chemical formulas from mass percentages of individual elements.
• Reveals relative percentages of each atom, % can fine molar ratios.

Molecular Formula

C6H12O6

Empirical Formula

Tells us the simplest whole number ratio of atoms in a chemical formula.

CH2O

Ionic

Gives us our whole chemical formula.

Molecular

Only know that we have ratios.

When calculating empirical formulas, round numbers close to whole numbers. If the decimal is ambiguous, then multiple to give us a whole number ratio.