Chemistry Honors - Unit 2 Vocab

Bohr model

simple model of an atom in which an electrons are on rings of different energies and protons and neutrons are in a very dense nucleus

proton

have a mass of 1 AMU, positive charge, located in nucleus

neutron

have a mass of ~1 AMU, neutral charge, located in nucleus

electron

have a mass of ~0 AMU, negative charge, located in electron cloud (on rings of discrete energy levels); are what drive chemistry

isotope

two or more of the same element but with different mass numbers (# of neutrons is different); both could be stable OR both could be unstable OR a mix

AZX notation

a way to summarize atomic properties with a symbol; a standard way to represent isotopes

mass number

a whole number determined by proton and neutron count added together

atomic number

the number of protons in an atom

average atomic mass

the weighted average mass of an element’s isotopes; explains why mass values on the periodic table have decimals; (% abundance of isotope A)(mass # of isotope A) + (% abundance of isotope B)(mass # of isotope B

atom

the smallest unit of an element; the number of protons, neutrons, and electrons in an atom dictate which element it is, its mass, its chemical reactivity, and atomic stability

ion

charged version of an atom

Aufbau principle

electrons will always fill lowest energy orbitals first before fillings higher energies

Hund’s rule

electrons filling the same sublevel will singly-occupy orbitals before doubling up (spin up before spin down)

Pauli-Exclusion Principle

no two electrons can have all four quantum values be the same (no orbital can have the same spin on both electrons - opposite spins)

orbital diagram

a model showing electron locations; shows their ground state

paired electrons

when two electrons are in one orbital; spin opposite

unpaired electrons

when one electron is in an orbital; spin clockwise (up)

valence electrons

all the electrons within orbitals on the highest energy level (n)

—> farthest from the nucleus

core electrons

all electrons within orbitals closer to the nucleus than the highest energy level (n); anything but valence

discrete energy levels

integer values representing fixed energy levels/rings of energy that electrons can be on (electrons cannot be in between two energy levels)

electron configuration

a faster method of orbital diagramming; leaves out some information including electron spin and the specific orbitals in a sublevel

orbital

a 3-D space with a specific quantized energy

quantized energy

energy that is not continuous, but exists in discrete packets; electrons matching this value are more likely to be found in that orbital

quantum model

described an atom by portraying electrons as wave-like entities located in probabilistic locations known as orbitals

electromagnetic radiation

energy that has wave-like behavior; contained within a photon

wavelength

the distance between successive crests/troughs of a wave (measured in nanometers or meters)

frequency

the number of wave cycles that pass a give point per unit of time (measured in Hertz)

photon

the basic particle of light; electromagnetic particle with energy

ground state

the lowest possible energy level that en electron can exist in

excited state

when an electron gains enough energy from an outside source so that it can exist in a different orbital