Chapter 1 - Kaplan MCAT Gen Chem Review

2025-2026

mass of 1 proton

1 amu

the number of electrons is equal to the number of

protons

protons + neutrons =

atomic mass / mass number

atomic weight

-constant

-avg of all the diff isotopes

Z

atomic number

A

mass number

hydrogen isotopes

-protium

-deuterium

-tritium

protium

hydrogen isotope with 1 proton

deuterium

hydrogen isotope with 1 proton and 1 neutron

tritium

hydrogen isotope with 1 proton and 2 neutrons

isotopes exhibit similar __ but different _

properties, mass

longer half life = more/less abundant

more

half life corresponds with

stability

avogadro’s number

6.02 × 10²³

energy of a quantum formula

E = hf

h

planks constant

planks constant

6.626 × 10^-34

f (sometimes v)

frequency of radiation

angular momentum of an electron orbiting a hydrogen nucleus formula

L = (nh)/(2π)

n

principal quantum number (any pos integer)

energy of an electron formula

E = - (R_H) / (n²)

R_H

rydberg unit of energy

rydberg unit of energy

2.18 × 10^-18

energy of an electron increases/decreases the farther from the nucleus it is

increases (n increases)

ground state of an atom

n=1

state of lowest energy

room temperature

excited state of atoms

-caused by heat or other energy

-when at least 1 electron moves to higher energy subshell

-brief

electromagnetic energy of photons formula

E = (hc) / λ

c

speed of light in a vacuum

speed of light in a vacuum

3.00 × 10^8 m/s

λ

wavelength of the radiation

line spectrum

each line on the emission spectrum corresponds to a specific electron transition

atomic emission spectrum

a fingerprint for element

(each element can have electrons excited to dif levels)

lyman series

the group of hydrogen emission lines corresponding to transitions from energy levels in n >= 2 to n=1

balmer series

the group of hydrogen emission lines corresponding to transitions from energy levels in n >= 3 to n=2

paschen series

the group of hydrogen emission lines corresponding to transitions from energy levels in n >= 4 to n=3

energy of emitted photon corresponds to dif in energy between __ and _

n_i and n_f

absorption spectrum

exciting the electrons results in energy absorption at specific wavelengths

wavelengths of absorption =

= wavelengths of emission

for electrons to move levels

must absorb exact right amount of energy

energy transition of valence electron formula

E = R_H [ (1/n_i²) - (1/n_f²) ]

energy state

the position and energy of an electron described by its quantum numbers (n, l, m_l, m_s)

values of the quantum numbers give info about the ____ of the orbitals

size, shape, and orientation

larger n =

= higher energy level and higher radius of electron’s shell

maximum number of electrons per shell formula

2n²

l

azimuthal quantum number (angular momentum)

azimuthal quantum number refers to

shape and number of subshells within a given principal energy level

azimuthal quantum number can be __ or _

0 or n-1

spectroscopic notation

l=0=s

l=1=p

l=2=d

l=3=f

l value increase =

= subshell energies increase

maximum number of electrons in a subshell formula

4l+2

M_l

magnetic quantum number

magnetic quantum number

the orbital within a subshell where an electron is found at a given moment

max electrons per M_l orbital

2

M_l can be equal to or between

-l and +l

s subshell shape

spherical

p subshell shape

dumbell

M_s

spin quantum number

the 2 spin orientations of M_s

+1/2 and -1/2

if 2 electrons are in the same orbital

spin opposite directions

if electrons in different orbitals have same M_s value

spin parallel

lower value of n+l

lower energy of subshell

if 2 subshells have same n+l value

lower n = lower energy and will fill w electrons first

s subshell max electrons

2

p subshell max electrons

6

d subshell max electrons

10

f subshell max electrons

14

anions

-negatively charged ions

-have additional electrons

cations

-positively charged ions

-remove electrons from subshells w highest n value and highest l value among these

orbitals per subshell formula

2l+1

hunds rule

within a subshell, orbitals are filled so that there are a max number of half filled orbitals

subshells may be listed in the order they fill or by

grouping same n together

half-filled and fully filled orbitals have

lower energy (more stable)

maximum number of electrons in an orbital formula

2n²

number of orbitals in a shell formula

n²

paramagnetic

-magnetic

-unpaired electrons

diamagnetic

-repels magnetic

-paired electrons

valence electrons

electrons in outermost shell of atom

most easily removed electrons

valence electrons

electrons available for bonding

valence electrons

electrons that dominate chemical behavior of atom

valence electrons

octet rule

atoms tend to have 8 valence electrons

when atoms have less than 8 valence electrons

react to become more stable

all elements in period 3 and below (octet rule)

can hold more than 8 electrons in valence shell