AP chemistry unit 1

molar mass

g/mole (values from periodic table)

molecular mass

amu (values from periodic table)

formula unit

the lowest whole-number ratio of ions in an ionic compound

mass number

sum of protons and neutrons in the atoms

isotope

atoms of the same element that have different numbers of neutrons

atomic number

number of protons in the atom

average atomic mass

the average mass of all the atoms of an element calculated as a weighted average of all isotopes

mass spectrometer

used to analyze the relative abundance of isotopes in a sample

law of constant composition/definite proportions

different samples of a chemical compound always have the same percent composition of elements

atomic theory

1) all elements are composed of atoms 2) atoms cannot be created or destroyed in a chemical reaction 3) all compounds have a fixed ratio of atoms of elements

empirical formula

shows the lowest ratio of elements in a compound

molecular formula

shows the actual ratio of elements in a compound

what are the two types of matter?

pure substances and mixtures

what are the two types of pure substances?

elements and compounds

what are the two types of mixtures?

homogenous (ex: solution) and heterogenous (non-uniform)

how do you determine the purity of a compound in a mixture?

perform an elemental analysis on the sample

coulombs law

electric force between charged objects depends on 1) the distance between the objects 2) the magnitude of the charges (trumps #1 in impact!!)

aufbau principle

electrons are added to sublevels in a specific order of increasing energy

hund's rule

no electron can be paried until every orbital in the sublevel has been occupied

2p and 3s are examples of

sublevels

electron "shells" 1 and 2 are examples of

energy levels

pauli exclusion principle

no two electrons in an atom can have the same quantum states so they must spin in opposite directions

paramagnetic atom

has one or more unpaired electrons

diamagnetic atom

has no unpaired electrons

orbital

a region of space where you are most likely to find an electron

isoelectronic

same electron configuration

first ionization energy

energy required to remove the outermost electron in an atom in its gaseous form

effective nuclear charge

a measure of the protons' pull on the electrons in the electron cloud

where on the periodic table are atomic radii bigger/smaller?

bigger in the bottom left, smaller in the top right

anion

a negatively charged atom

cation

a positively charged ion

are cations or anions smaller?

cations

electronegativity

a measure of how well an atom can attract an electron

valence electrons

electrons located in the outermost occupied energy level of an atom

core electron

electrons located in the inner energy levels of an atom

elements in the same group are usually

chemically very similar