Ap chem unit 1

Isotopes

Atoms of the same element that have different numbers of neutrons

atomic number

number of protons

Mass number

# of protons + neutrons

atomic mass

the weighted average of the masses of the isotopes of an element

- calculated using isotope abundance

- avg. Mass= (mass1)(%)+(mass2)(%)

Mass Spectroscopy graph

relative abundances and masses of isotopes of an element.

- IADD ( Ionization Acceleration Deflection Detection)

- x axis is mass

- y axis is abundance (%)

Percent comp

what percent of its total mass comes from each element

empirical formula

a formula with the lowest whole-number ratio of elements in a compound

- determined form percent comp

molecular formula

show the actual molecule

- determined by (empirical to Molecular)

1. given molecular weight of substance

2. ration of molecular weight/ empirical formula - must be a whole number

3. multiply the ratio by empirical formula

Photoelectron Spectroscopy

refers to energy measurement of electrons emitted from solids, gases or liquids by the photoelectric effect, in order to determine the binding energies of electrons in a substance.

Coulomb's Law

- higher charges and smaller distance between charges create a stronger electrostatic force

- lower charges and larger distance between charges create a weak electrostatic force

- can explain to the periodic trends

Ionization energy

energry required to remove a electron from an atom

increases across a period

- increasing effective nuclear charge (the more you go the stronger elements want to keep their electrons bc they wanna be stable - more energy)

decreases down a group

- more PELs (the farther away the electron is from the nucleus the easier it is to take it - little energy)

atomic radius

distance form the nucleus to the outer most electrons

decreases across a period

- increasing effective nuclear charge

- valence electrons are drawn closer to the nucleus, decreasing the size of the atom

Increases down a group

- increases in the orbital sizes bc of principal quantum levels

ionic radius

Anions- larger than parent atom

Cation- smaller than the parent atom

Molarity

unit of concentration

electron configuation

list of shells, subshells, and orbitals electrons in an atom occupy

The Aufbau Principle

the rule that electrons occupy the orbitals of lowest energy first then occupy of increasing energy

The Pauli Exclusion principal

two electrons in the same orbital cannot have the same spin

Hund's principal

Electrons in a subshell will occupy empty obitals first then pair up

periodic trends

1. electrons attracted to the protons

- electron and nucleus close are strongly attracted

- more protons more strongly attracted the electron is

2. valence electrons don't feel the full pull of the nucleus b/c inner core push them away, they experience effective nuclear charge

3. add or subtract electrons to be stable

Electronegativity

measures how strongly an atom attracts valence electrons in covalent bonds

Increases across a period and decreases down a group

electron affinity

change in energy when a atom gains an electron

increases across a period and decreases down a group

Hydrate

ionic compound that contains water molecules in its structure

anhygdrate

substance that remains after water is removed