Chemistry/Physics MCAT

molecules with an even distribution of electrons are….

nonpolar

molecules with an uneven distribution of electrons are….

polar

From where are electrons taken or added?

the valence shell 

equation for energy of a photon

E=hc/wavelength

h is planck’s constant = 6.63 × 10⁻³⁴

c is the speed of light = 3.0 × 10⁸ m/s

what does electronegativity do for electron distribution?

a less electronegative atom will have a more even electron distribution

principle quantum number

The main energy level or shell the electron occupies. It determines the primary energy and size of the orbital; it is the highest numbered shell currently occupied in its ground state

Higher values mean the electron is farther from the nucleus, has higher energy, and is in a larger orbital 

angular momentum quantum number

the subshell and the shape of the orbital within a given shell n. 

l=0 corresponds to the s subshell 

l=1 corresponds to the p subshell 

l=2 corresponds to the d subshell 

l=3 corresponds to the f subshell 

magnetic quantum number

The orientation of the orbital in 3D space. It determines the number of orbitals within a subshell (l)

if l=0 (s subshell), m1 can only be 0

if l=1 (p subshell), m1 can be -1, 0, and +1, meaning there are three p orbitals all of which can be occupied by at most 2 electrons

if l=2 (d subshell), m1 can be -2, -1, 0, +1, and +2, meaning there are 5 d orbitals all of which can be occupied by at most 2 electrons

spin quantum number

the intrinsic angular momentum of the electron, referred to as its spin, creating a small magnetic field

only two possible values: +1/2 and -1/2

bohr’s model

a model of the atom that explains the stability of electrons and the origin of atomic emission spectra. 

1. quantized orbits 

2. quantized angular momentum 

3. no energy change within an orbit 

4. transitions (absorption and emission) - an atom absorbs a photon with energy E=hv; an atom emits a photon when an electron falls from a higher-energy orbit to a lower-energy orbit 

Aufbau principle

a set of rules used to determine the electron configuration of an atom in its ground state.

Core idea: electrons first occupy the lowest energy orbitals available before filling higher energy orbitals and they are filled in the order of increasing energy

quantized nature of electronic transitions

This concept states that an electron in an atom can only exist in discrete, specific energy levels and not in the spaces between them.

Core idea: energy is not continuous but exists in tiny indivisible packets called quanta

heisenberg uncertainty principle

A principle essentially stating that it is impossible to simultaneously know the exact position and the exact momentum of a particle with perfect accuracy.