Econ AP

I. Atoms

a. Smallest unit of matter

b. Made of protons electrons and neutrons

c. Has protons and neutrons packed together in a nucleus

d. The electrons orbit around

e. Atomic number

i. Written as a subscript next to the symbol of an element

ii. Number of protons (and hence number of electrons) of a neutral element's atom

f. mass number

i. sum of protons and neutrons, written as a superscript to the left of an element's symbol

g. atomic weight

i. approximation of the total mass of an atom

h. isotopes- atoms of the same element that have a different number of neutrons and hence weigh more.

i. Can be:

1. stable

2. radioactive

a. the nucleus decays spontaneously

i. energy levels

i. energy- ability to do work

ii. different electron orbitals with different states of potential energy are energy levels

iii. electrons on outermost orbitals are valence

iv. electrons have orbitals

1. 2 electrons per orbital

2. an almost defined area in which electrons can travel

3. can be more than one orbital per shell

II. Molecules

a. Atoms connected by chemical bonds

b. Covalent bond

i. Sharing of a pair of valence electrons by two atoms

ii. More than one pair of electrons can be shared

iii. The number of covalent bonds an atom can make is called its valence

1. i.e. oxygen has a valence of 2

iv. there can be polar covalent bonds

v. electro negativity is the attraction of an atom for the covalently bonded electrons

vi. nonpolar covalent bonds have equally electronegative covalently bonded atoms

c. ionic bonds

i. where