Physical Science Moles

Atomic number- number of protons in that atom  Represented by “Z” Ex) Z=11 Mass number- number of protons and neutrons  Represented by “A” Ex) A=19

Calculating # of neutrons Mass number (A) : - Atomic number (Z): ______________________ Number of neutrons:

Average atomic mass An element’s average atomic mass is a weighted average of the masses of its naturally occurring isotopes.  Unit : amu

Properties of Metals Shiny, malleable, ductile, good conductors of heat and electricity  Alkali metals-react violently with water (very reactive b/c has 1 valence electron Na + )  Alkaline earth metals- (reactive usually 2 valence electrons Mg 2+)  Transition metals- not as reactive Au, Ag will form cations (ex. Au 3+ )  Semiconductor can conduct under certain conditions

Properties of Nonmetals All except for hydrogen are found on the right side of the periodic table. Can be solids, liquids, gases  solids are usually dull, brittle and poor conductors of electricity and heat.

Nonmetals Halogens – very reactive, generally accept electrons Cl -, F -, I - Noble Gases- exist as single atoms instead of molecules. Generally do not react because s and p orbitals are full.  Ex) Ne, Ar, He

Moles Return to the metric system!!! Mole-abbreviated mol  A collection of a very large number of particles about =??? Avagadro’s constant- the number of particles in 1 mol of a pure substance

Why 6.022x10 23 ? The mole is defined as the number of atoms in g of carbon-12.  Experiments show that 6.022x10 23 is the number of carbon-12 atoms in 12.00g of carbon-12  One mole of carbon consists of 6.022x10 23 carbon atoms with an average atomic mass of amu

Molar mass The mass in grams of 1 mol of a substance.  1 mol of carbon-12 atoms has a molar mass of 12.00g.  But a mole of an element will usually include atoms of several isotopes.  So the molar mass of an element is the same as its average atomic mass in amu.  Carbon is 12.01amu, one mole of carbon has a mass of 12.01g

Conversion factors A ratio derived from the equality of two different units and that can be used to convert from one unit to another Amount (mol)  Mass g amount (mol)x molar mass of element 1 mol of element Mass g  Amount (mol)

Examples What is the mass of 5.50 mol of iron?  Using periodic table, find iron  Average atomic mass = amu  So molar mass = g/mol Fe  Now, set up problem 5.50mol Fe x g Fe = 307 g Fe 1 mol Fe