atomic number (Z)

# of protons

atomic mass / mass #

# of protons + neutrons (in amu)

atomic weight

weighted average of isotopes

Plank's quantum theory

energy emitted as EM radiation from matter exists in discrete bundles called quanta (E=hf)

Bohr's model of a hydrogen atom

possible values for the angular momentum of an electron orbiting a hydrogen nucleus depends on n (principle quantum number)

- angular momentum of an electron changes only in discrete amouns with respect to n

Energy of the electron

E is directly proportional to n

E=-RH/n^2

- energy of electron changes in discrete amounts with respect to the quantum number
- energy increases the farther out from the nucleus is

applications of Bohr model

as electrons go from lower energy to hgiher energy level, they get **AHED**:

- Abosrb light
- Higher potential
- Exctied
- Distant

Atomic emission spectra

electrons in an atom can be excited to different energy levels... but when electrons return to their ground states, they emit a photon with a wavelength characteristic of the specific energy transition it undergoes

E=hc/wavelength

Lyman series

group of hydrogen emission lines corresponding to transitions betwen upper levels n>1 to n=1

- larger energy transitions so shorter photon wavelenghts in the UV region of the EM spectrum

Balmer series

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

Paschen series

transitions from n>3 to n=3

- smaller energy transition so longer photon wavelenghts in the visible region

Atomic Absorption Spectra

when an electron is excited to a higher energy level, it absorbs exactly the right amount of energy to make that transition

Heisenberg uncertainty principle

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

principle quantum number (n)

shell

- the larger the integer of n, the higher the energy level and radius of the electron's shell
- max # of electrons within a shell 2n^2

angular momentum quantum number (l)

refers to the shape and number of subshells within a given pricnipal energy level

- l=0 to n-1
- s: l=0
- p: l=1
- d: l=2
- f: l=3
- max # electrons within a subshell=4l+2

magnetic quantum number (m_{l})

specifies particular orbital within a subshell where an electron is most likely to be found at a given moment in time

- m
_{l }is an integer between -l and l

spin quantum (m_{s})

spin orientation

- +1/2 or -1/2

n+l rule

the lower the values for the first 2 quantum numbers (n+l), the lower the energy of the subshell

anions & cations

anions fill the same way, but for cations start with neutral atom and remove elctrons from the subshells with the highest value for n first

Hund's rule

within orbitals, parallel spins filled first... half-filled and fully-filled orbitals have lower energy energies (higher stability)... 2 exceptions:

- Chromium: [Ar]4s
^{1}3d^{5}rather than [Ar]4s^{2}3d^{4}^{ }because of stability - Copper: [Ar]4s
^{1}3d^{10}rather than [Ar]4s^{2}3d^{9 }because of stability

paramagnetic

unapired electrons... magnetic attraction

diamagnetic

only paired electrons so slightly repelled by a magnetic field