Chemistry: Atomic Structure, Electron Configuration, and Periodic Trends

Atomic number (Z)

Number of protons in an atom; also equals number of electrons in a neutral atom

Mass number (A)

Total number of protons plus neutrons in an atom

Isotopes

Atoms of the same element (same number of protons) with different numbers of neutrons

Formula for neutrons

Neutrons = Mass number (A) minus Atomic number (Z)

Formula for ion charge

Charge = number of protons minus number of electrons

Cation

A positively charged ion; has fewer electrons than protons

Anion

A negatively charged ion; has more electrons than protons

Isoelectronic

Atoms or ions that have the same number of electrons as each other

Speed of light (c)

3.00 x 10^8 m/s

Planck's constant (h)

6.63 x 10^-34 J·s

E = hv

Equation relating a photon's energy to its frequency

c = (lambda)(v)

Equation relating speed of light to wavelength and frequency

E = hc / (lambda)

Equation relating a photon's energy directly to its wavelength

Relationship between wavelength and energy

Shorter wavelength means higher frequency and higher energy

Order of visible light by energy (low to high)

Red, orange, yellow, green, blue, violet

Why elements have unique line spectra

Each element has a fixed, unique set of allowed electron energy levels, so it emits only specific photon energies

s orbital shape

Sphere

p orbital shape

Dumbbell shape with two lobes

d orbital shape

Mostly four lobed cloverleaf shape

Electrons in an s subshell

Maximum of 2

Electrons in a p subshell

Maximum of 6

Electrons in a d subshell

Maximum of 10

Electrons in an f subshell

Maximum of 14

Order of orbital filling

1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d

Valence electrons

Electrons in the outermost occupied shell of an atom

Paramagnetic

An atom or ion with at least one unpaired electron; weakly attracted to a magnetic field

Diamagnetic

An atom or ion with all electrons paired; not attracted to a magnetic field

Atomic radius trend across a period

Decreases going left to right across a period

Atomic radius trend down a group

Increases going down a group

Radius trend for isoelectronic species

The ion or atom with the fewest protons has the largest radius

Ionization energy trend

Generally increases left to right across a period and decreases down a group

Electron affinity trend

Generally increases left to right across a period and decreases down a group

Electron affinity of halogens

Very high, because they need only one more electron to complete a noble gas configuration

Density formula

Density equals mass divided by volume

Sig fig rule for multiplication and division

Answer has the same number of significant figures as the factor with the fewest significant figures

Sig fig rule for addition and subtraction

Answer has the same number of decimal places as the number with the fewest decimal places

Metric prefix kilo

10^3, symbol k

Metric prefix centi

10^-2, symbol c

Metric prefix milli

10^-3, symbol m

Metric prefix micro

10^-6, symbol (mu)

Metric prefix nano

10^-9, symbol n

Metric prefix pico

10^-12, symbol p

Nuclide symbol notation

Mass number written on top left, atomic number written on bottom left, of the element symbol

Noble gas shorthand electron configuration

Start with the nearest preceding noble gas in brackets, then continue filling orbitals from there