Chem Unit 1

review notes, labs, handouts

atomic structure

protons and neutrons form nucleus, electrons orbit the nucleus

atomic number

the number of protons

atomic mass

the number of protons and neutrons in the nucleus

average atomic mass

the average atomic mass of all known atoms of that element; most stable with a mass of the nearest whole number

unit for atomic mass

amu

ion

atom with a charge (# electrons ≠ # protons)

cation

positively charged ion (more protons than electrons)

anion

negatively charged ion (more electrons than protons)

isotope

atoms that have the same number of protons, but have a different number of neutrons

nuclear notation

mass number on top left, atomic number on bottom left, element symbol on the right

how to calculate average atomic mass

add (percent abundance) * (mass) for each isotope

Schrodinger

developed quantum wave equation

Bohr

found that electrons move in specific orbits around the nucleus

Chadwick

discovered neutrons

Dalton

created dalton atomic theory

Rutherford

gold foil experiment; proposed protons & neutrons are in the nucleus of an atom

Thomson

plum pudding model; discovered electrons

nuclear fission

splitting of nucleus into smaller fragments, releasing energy

example of nuclear fission

nuclear power plants

nuclear fusion

light mass nuclei combine together and releases more energy than fission

example of nuclear fusion

hydrogen bomb, sun

nuclear half life

time required for half the atoms of a particular radioisotope to decay into another isotope

alpha decay

emits helium

beta decay

emits an electron

gamma decay

emits energy with no charge or mass

positron/beta plus decay

emits positron (positive electron)

neutron emission

neutron emitted

band of stability

line showing where elements are most stable (neutrons vs protons)

where do you undergo beta decay

elements above the band of stability

where do you undergo positron decay

elements below the band of stability

when do you undergo alpha decay

when the element has more than 82 protons

electromagnetic spectrum

range of all types of radiation

what type of radiation has the longest wavelength and lowest frequency

radio

what type of radiation has the shortest wavelength and highest frequency

gamma

what happens when the electrons of an element is heated up?

the electrons get excited and jump up an energy level, when they fall back down light is produced

what are the orbitals and how many electrons can they hold

s (2 electrons), p (6 electrons), d (10 electrons), f (14 electrons)

aufbau principle

electrons enter lowest energy orbitals first

pauli exclusion principle

atomic orbital may have up to 2 electrons, spins must be paired in opposite directions

hund's rule

fill orbitals halfway first, then pair electrons

what are exceptions to electron configuration?

silver and chromium have the s and d swapped at the end

atomic radius

how large the radius of an atom is (how big the atom is)

atomic radius trend

increases as you go down, decreases as you go across

proton pulling

as protons increase, they pull the electrons closer to the nucleus

ionization energy

the amount of energy required to remove a valence electron

electron shielding

outer electrons have less of an attraction to the nucleus because the inner electrons “shield” them

ionization energy trend

decreases as you go down, increases as you go across

electronegativity

ability of an atom to attract an electron

electronegativity trend

decreases as you go down, increases as you go across, noble gases have an electronegativity of 0

what element is the most electronegative?

fluorine