Unit 1: Atomic Structures & Properties

Pauli Exclusion

Atomic orbitals can hold at most 2 electrons

Coulombs

Larger charges and smaller distances result in a stronger force, while like charges repel and opposite charges attract

Aufbau principle

Electrons fill the lowest energy orbitals first

Hunds rule

When filling a subshell of orbitals with the same energy, electron will first occupy each orbital singly before any orbitals is doubly occupied. Thus minimizes electron repulsion and is more stable

Photoelectric spectroscopy

Atomic number

Number of protons

Atomic mass/ Mass number

Sum of protons and neutrons

Mass spectrum to determine Average atomic mass

Mass number × % expressed as a decimal

Pure substance

Only one type of matter (single element or compound)

Mixtures

Can be physically separated ( homogeneous & heterogeneous)

Determining moles of atoms

Divide given grams by molar mass to get moles then multiply moles by 6.02 × 10²³ atoms

Calculating mass of ions present

Given number of moles × 1 mol (ion)/1 mol (moles) × molar mass of CO3 = answer

Mass percent

Mass of desired element/ total mass of compound × 100%

Empirical/ molecular formula

Calculating empirical/molecular formula of unknown hydrocarbons

Atomic radius

Radius increase as you go down a group due to adding shells; radius decreases as you go right due to more protons pulling more protons closer to nucleus. Increase down and left

Ionic radius

Losing electrons means the protons pull on fewer electrons so the radius contracts; gaining electrons means more electron repulsion so radius expands

Isoelectronic species

Atoms/ions with same electron configuration

Ionization energy

Increases going up and right due to the energy required to remove an electron due to valence electrons being tighter and harder to pull

Electron Affinity

Energy associated with adding an electron opposite of ionization energy; increases up and right (no noble gases)

Electronegativity

How well an atom can attract electron density; more strongly attracting electron density means more electronegativity. Increases up and right (no noble gases) more nucleus can pull, more electronegative

Nonmetals

Tend to form anions, poor conductors of heat, tend to gain electrons

Metals

Tend to form cations, good conductors of heat and electricity, compounds formed between metals and non metals tend to be ionic

Group 1A: Alkali Metals (+1)

Reactions with water are exothermic, found only in compounds in nature, low densities and melting points

Group 2A: Alkaline Earth Metals (+2)

Less reactive with water than Alkali, reactivity tends to increase as you go down the group, have higher densities and melting points than Alkali

Group 6A: (Chalcogens)

Contains multiple Allotropes (different forms of the same element in the same state)

Group 7A: Halogens (-1)

Typical non metals, react directly with metals

Group 8A: Noble Gases

Large ionization energy, relatively unreactive