Periodic Trends

Atomic Radius

the total distance from an atom’s nucleus to the outermost orbital of electrons

Ionic Radius

One-half the diameter of an ion (size of an atom after it becomes an ion)

First Ionization Energy

amount of energy needed to remove one electron from an atom

Electronegativity

how strongly an atom pulls electrons toward itself when it’s sharing them in a bond

Metallic Character

the tendency of an element to lose electrons and form positive ions or cations

Cation

positively charged atom (smaller=lose electrons)

Anion

negatively charged atom (bigger=gain electrons)

Trends that decrease across periods —>

Atomic Radius, Metallic Character

Trends that increase across periods —>

Electronegativity, First Ionization Energy

Trends that increase as you move down groups

Atomic Radius, Metallic Character

Trends that decrease as you move down groups

Electronegativity, First Ionization Energy

Core Electrons

electrons in the innermost energy levels

Valence Electrons

electrons in the outermost energy level

Hund’s Rule

electrons only pair within the orbitals when all are half-full

Aufbau’s Principle

certain order that electrons enter energy levels (1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s…)

Pauli Exclusion Principle

in pairs of electrons, one must spin counterclockwise while the other spins opposite (clockwise)

Ground State

state of electrons before and after their excited state

Excited State

electrons start jumping to higher energy levels and emitting photons