Notes

molecule - 2 or more elements combined; elements can be the same or different (compound)

chemical bonds - the sharing or transfer of electrons to attain stable electron configurations for the bonding atoms; force that holds atoms together in compounds; lower the potential energy of the charged particles

types of chemical bonds:
a) ionic bond - bond that forms btwn a metal & nonmetal; metals lose electrons & become cations (positively charged ions) while nonmetals gain electrons & become anions (negatively charged ions); oppositely charged ions attract to form ionic compounds
b) covalent bond - bond that forms btwn two or more nonmetals; atoms share electrons, forming molecules & molecular compounds

chemical formula - symbolic representation of a compound that indicates the elements present & relative # of atoms of each
-elements usually listed in order of most metallic (positively charged) to least metallic (negatively charged)

types of chemical formulas:
a) empirical formula - shows relative # of atoms of each element in compound (HO)
b) molecular formula - shows actual # of atoms of each element in compound (H2O2)
c) structural formula - uses lines to represent covalent bonds & show how atoms are connected to e/o (H-O-O-H); singles lines - single bond (1 shared electron pair), double lines = double bond (2 shared electron pairs)

types of molecular models:
a) ball-and-stick - represents atoms as balls & chemical bonds as sticks to show how atoms are bonded & the compound's shape
b) space-filling - represents how atoms fill the space btwn e/o; estimates molecule appearance if scaled to size
c) lewis structure - chemical bonding model that uses diagrams to represent bonds btwn atoms as shared or transferred electorns; valence electrons are represented as dots
octet rule - tendency for most bonded atoms to have or share 8 electrons in their outer shell in order to obtain stable electorn configruations & lower their potential energy

ionic compounds

ionic compound formulas:
-ionic compounds always contain positive & negative ions
-in a chemical formula, the sum of the charges of the positive ions (cations) must = the sum of the charges of the negative ions (anions); compound is electrically neutral
-the formula of an ionic compound reflects the smallest whole-# ratio of ions

writing ionic compound formulas:
1. write the symbol for the metal cation & its charge followed by the symbol for the nonmetal anion & its charges; determine charges from the element's group # in the periodic table
2. adjust the subscript on each cation & anion to balance the overall charge
3. check to make sure the sum of the charges of the cations = the sum of the charges of the anions; the charges cancel

naming ionic compounds:
ionic compounds are categorized into two types:
1. the metal forms only 1 type of ion; since the charge of the metal ion is always the same, it doesn't need to be specified in the name
2. the metal forms more than 1 type of ion; the charge can differ in different compounds, so it must be specified in the name
(slide 19)

binary compounds - a compound that contains only 2 different elements
naming binary ionic compounds containing a metal the forms only 1 type of cation:
[name of cation (metal)][base name of anion (nonmetal)+-ide]
naming binary ionic compounds containing a metal the forms more than 1 type of cation:
[name of cation (metal)][(charge of cation (metal) in roman numerals in parentheses)][base name of anion (nonmetal)+-ide]
-the cation charge can be inferred from the sum of the charges of the nonmetal anions; the sum of all charges in the compound must be 0

naming ionic compounds containing polyatomic ions:
polyatomic ion - an ion composed of 2 or more atoms
-name of polyatomic ion is incorporated whenever it occurs
(slide 20)

hydrated ionic compounds
hydrates - an ionic compound that contains a speicifc # of water molecules associated /w each formula unit; formula is written /w a dot before the water molecule(s) included
naming hydrates: [anyhdrous (w/o water) compound name][prefix for the # of water molecules]["hydrate"]

molecular compounds

covalent bonding:
bonding pair - pair of electrons shared btwn 2 atoms
lone pair (nonbonding electrons) - pair of electrons assoicated /w only 1 atom

types of covalent bonds:
a) single bond - 2 atoms share 2 pair of electrons
b) double bond - 2 atoms share 2 pairs of electrons
c) triple bond - 2 atoms share 3 pairs of electrons

naming molecular compounds:
1. write name of the element /w the smallest group # first
2. if the 2 elements are in the same group, write the element /w the greatest row # first
3. the prefixes of each element indicate the # of atoms present

[prefix][name of 1st element][prefix][base name of 2nd element+-ide]

formula mass & the mole concept for compounds
mass compound -> mol of compound -> # of molecules
molar mass avogadro's #

formula mass = (# of atoms of 1st element in chemical formula * atomic mass of 1st element) + (# of atoms of 2nd element in chemical formula * atomic mass of 2nd element) +...

composition of compounds
mass percent composition - an element's % of the total mass of a compound containing the element
mass compound -> mol compound -> mol element -> mass element

mass percent of element X = (mass of element X in 1 mol of compound/mass of 1 mol of compound) *100

finding an empirical/molecular formula from data:
1. convert percentage masses to grams (if not given, assume 100 g of compound)
2. convert each mass (grams) to moles /w the molar mass for each element as a conversion factor
3. divide all the subscripts (# of moles of each element) by the smallest subscript
4. if the subscripts aren't whole #s, multiply all the subscripts by a small whole # to determine whole-# subscripts