Isotope l The average atomic mass of each element uses the masses of the various isotopes of an element l An isotope of an element is the same element with the same # of p +, but a varying number of neutrons and thus a varying atomic mass l NOT all elements contain isotopes

Isotope Determination ex. H There are 3 isotopes of Hydrogen atomic mass atomic # #p + #n H H H The average atomic mass of H =

Isotope Determination There are three isotopes of Carbon 12 CCarbon CCarbon CCarbon 14

Groups - # valence e - Periods - Size of atom Noble gases Group VIII Halogens Group VII Alkalli Metals Group I Metals Nonmetals Metalloids Alkali Earth Metals Group II

Formula Weights H2H2 N2N2 O2O2 F2F2 Cl 2 Br 2 I2I2

Chemical Equations Sodium + Diatomic Chlorine > Sodium Chloride Reactant(s) yields -----> Product(s) Na + Cl > NaCl Equations must be balanced due to the Law of Conservation of Matter

Chemical Equations Bookkeep the Atoms Count the individual atoms of reactants and products line up under each atom in separate rows: Na + Cl 2 NaCl 1 Na 2 Cl 1 Cl Use whole number multipliers to equalize the atoms of reactants and products. Place these whole number prefixes before the element or the compound

Chemical Equations Bookkeep the Atoms Na + Cl 2 NaCl 1 Na 1 Na 2 Cl 1 Cl

Chemical Equations 2Na + Cl 2 2NaCl 2 Sodium atoms react with 1 chlorine molecule to form 2 “Molecules” of Sodium Chloride

Chemical Equations 1. (NH 4 )SO 4 H 2 SO 4 + NH 3 5. Fe + H 2 O Fe 3 O 4 + H 2 TRY in groups #6 and #9

% of an Element in a Compound (Elemental Analysis) l Mass of Element x 100 FW of Compound l % H in H 2 O 2H x 100 =2.00 amu x 100 = 11.1% H 2 O18.00 amu l % O in H 2 O O x 100 = amu x 100 = 88.89% H 2 O amu

Group Work l Determine the Elemental Analysis of: »C 6 H 12 O 6 »NH 3 »CO 2

Definition l Mole (mol or n) »1 mole contain the same number of entities (atoms, molecules, ions, particles) as there are in exactly grams of Carbon and a mole contains x number of entities. This number is called Avogadro’s Number.

1.00 g H g C 18.00g H 2 O g Cl g C 6 H 12 O x10 23 atoms x10 23 atoms x10 23 molecules x10 23 ions x10 23 molecules

Analogy l 1 pair = 2 l 1 trio = 3 l 1 dozen = 12 l 1 mol = x 10 23

Molar Mass (MM) To Determine the Molar Mass (MM): For an element - it’s the atomic weight in grams For a compound - it’s the formula weight in grams A mole contains Avogadro’s Number (6.022 x ) particles (atoms, ions, molecules).

Working with Moles l Formula given grams of a compound or element, determine the number of moles l Moles = grams MM OR l Dimensional Analysis

Working with Moles l Formula given moles of a compound or element, determine the number of grams moles (MM) = grams OR l Dimensional Analysis

Multiply by Avogadro’s #, Divide by Molar Mass Multiply by Molar Mass, Divide by Avogadro’s # Number of Moles Number of atoms, ions, molecules Mass in grams