Atomic Structure

MCAT Prep: General Chemistry Part 1

Atomic weight

the weighted average of the masses of the naturally occurring isotopes of an element, in amu per atom

Mole

a unit used to count particles and is represented by Avogadro’s number

6.022 x 10^(23)

Avogadro’s number

mass of a sample / molar mass

Moles equation

Isotopes

for a given element, multiple species of atoms with the same number of protons (same atomic number) but different numbers of neutrons (different mass numbers)

Planck’s quantum theory

energy emitted as electromagnetic radiation from matter exists in discrete bundles called quanta

E = (-RH)/(n²)

energy of electron

E = (hc)/(lambda)

electromagnetic energy of photons

Balmer series

the group of hydrogen emission lines corresponding to transitions from upper levels n > 2 to n = 2

Lyman series

the group corresponding to transitions between upper levels n > 1 to n = 1

Absorption spectrum

characteristic energy bands where electrons absorb energy

Heisenberg uncertainty principle

it is impossible to determine with perfect accuracy the momentum and the position of an electron simultaneously

Shell

Number: 1st

Symbol: n

Value: n

Subshell

Number: 2nd

Symbol: l

Value: from zero to n-1

Orbital

Number: 3rd

Symbol: m_l

Value: between l and -l

Spin

Number: 4th

Symbol: m_s

Value: +1/2 or -1/2

Principal quantum number (n)

the larger the integer value of n, the higher the energy level and radius of the electron’s orbit

2n^2

the maximum number of electrons in energy level n

Azimuthal quantum number (l)

refers to subshells. The four subshells corresponding to l = 0, 1, 2, and 3 are known as s, p, d, and f, respectively.

s

l = 0

p

l = 1

d

l = 2

f

l = 3

4l + 2

the maximum number of electrons that can exist within a subshell is given by this equation

Magnetic quantum number (m_l)

this specifies the particular orbital within a subshell where an electron is highly likely to be found at a given point in time

Spin quantum number (m_s)

the spin of a particle is its intrinsic angular momentum and is a characteristic of the particle, like its charge

Hund’s rule

within a given subshell, orbitals are filled such that there are a maximum number of half-filled orbitals with parallel spins

Valence electrons

electrons of an atom that are in its outer energy shell and that are available for bonding