1. elements are composed of indivisible particles-atoms. 2. atoms of the same element are alike in mass and size. 3. atoms of different elements are not alike – they have different masses and sizes. 4. compounds are union of two or more atoms of different elements. 5. compounds contain simple numerical ratios of atoms. 6. more than one compound can be formed of atoms of two elements. Dalton rules: Rutherford conclusions: 1. Atom has minuscule nucleus, smaller than the atom, containing all positive charge. 2. Electrons are negatively charged and orbit around atom nucleus. Mass of p is 1840 x mass of e- (1.67 x g). Ions are formed when an atom gains or looses electrons. Number of protons give the identity of the atom. Isotopes differ in number of neutrons and masses. U Mass # Atomic # Average atomic mass is the sum of masses of isotopes multiplied with its abundance. It is assumed that the masses of p and n are equal, and electron masses are ignored. Average mass of Cu is: ( x ) + (( x ) = Element Symbol Z mass# #p #n #e charge Bromine Br Sulfur S Z = #p. Mass# = #p + #n. charge = #p - #e.

Metal and nonmetal usually make an ionic compound. Nonmetals create covalent bonding. Metals create cations (group IA: 1+, group 2A: 2+), nonmetals produce anions (group VIA: 2-, group VIIA: 1-) as all elements tend to create electron configuration of their closest noble gas. Formula follows electronegativities of the elements. Binary, ionic compound: metal name unchanged, non- metal changes the ending to ide: Sodium chloride, NaCl. Transition metals contain charge in Roman numerals, Copper (II) oxide, CuO. Binary covalent compound: must give prefix how many atoms of each kind is in. N 2 O 5 : Dinitrogen pentoxide. Polyatomic ions: ammonium NH 4 +, carbonate, CO 3 2-, sulfate SO 4 2-, nitrate, NO 3 -, phosphate, PO The last three -ate anions have a similar –ite ion: same charge, one less oxygen atom in the formula. A compound must be neutral, so the sum of positive charges in an ionic compound must compensate the sum of negative charges. In Mg 3 (PO 4 ) 2. each Mg is 2+ charged, so the sum of positive charges is +6. Each (PO 4 ) ion is 3-, thus the sum of negative charges is 6-. Acids: If the acid contains no oxygen, make the name by prefix Hydro-, and suffix - ic acid. Hydrochloric acid, HCl. Oxyacids: If the anion ends with –ate, the acid ends with –ic. If the anion ends with –ite, the acid ends with -ous. Nitrate – nitric acid. Sulfite – sulfurous acid. Cation Anions SO 4 2- Cl - O 2- K + K 2 SO 4 KCl K 2 O H + H 2 SO 4 HCl H 2 O Zn 2+ ZnSO 4 ZnCl 2 ZnO Al 3+ Al 2 (SO 4 ) 3 AlCl 3 Al 2 O 3

Al + Fe 2 O 3  Fe + Al 2 O 3 22  (s)(s)(s)(s)(s)(s)(s)(s) Formulas (substances), coefficients and symbols (+,  ) make the core of a chemical equation. Physical state in parenthesis, conditions placed around  N 2 + H 2  NH 3 Step 2: Start balancing metal first. Continue with nonmetals other than O or H. 2 N: H: 2 2 N: H: Step 3: Balance O or H. if there is either O 2 or H 2 on the left side, balance it last. Step1: Count atoms on each side. Balancing Single-displacement reactions 2 Al(s) + Fe 2 O 3 (s)  Al 2 O 3 (s) + 2 Fe(l) Double-displacement reactionsPCl 3 (l) + 3 AgF(s)  PF 3 (g) + 3 AgCl(s) Decomposition reaction 2 HgO(s) 2 Hg(l) + O 2 (g) Heat Combination reaction H 2 (g) + I 2 (g)  2 HI(g) Single displacement reactions require that the free element is more reactive than the one in the compound. Element reactivity is found in metal activity series and halogen activity series. Double displacement reactions require that either formation of water (accompanied by heat), gas or precipitate occurs. CH 4 + 2O 2 → CO 2 + 2H 2 O kJ Energy of activation required to start a reaction. Heat is either absorbed (endothermic) or released (exothermic reaction). Heat can be placed in the equation.

s: 2 e - p: 6 e - d: 10 e - f: 14 e Period 1s 2 4s 2 4p 6 4d 10 4f 14 3s 2 3p 6 3d 10 2s 2 2p 6 Shells = periods (n= 1, 2, 3, …) Subshells = s, p, d, f Orbitals = electron pathways; each holds up to two electrons. s p d f S Fe S: 1s 2 2s 2 2p 6 3s 2 3p 4 = [Ne] 3s 2 3p 4 Fe: 1s 2 2s 2 2p 6 3s 2 3p 4 4s 2 3d 6 = [Ar] 4s 2 3d 6 Filling of the subshells: follow the periodic table 3d is filled in 4 th period 4f is filled in 6 th period 1234 Orbital diagram Electron configuration