Periodic Trends

Periodic law states that elements are arranged by

their atomic numbers with similar properties

occuring at regular intervals.

Definition: Half of the distance between nuclei in covalently bonded diatomic molecule Radius decreases across a period more p+ and e- for stronger magnetism.

Radius increases down a group Each row on the periodic table adds a “shell” or energy level to the atom

Atomic Radius

Table of Atomic

Radii

Period Trend:Atomic Radius

Tends to increase across a period As radius decreases across a period, the electron you are removing is closer to the nucleus and harder to remove

Tends to decrease down a group Outer electrons are farther from the nucleus and easier to remove

Ionization Energy

Definition: the energy required to remove an electron from an atom

Periodic Trend:Ionization

Energy

Electronegativity

Definition: A measure of the ability of an atom in a chemical compound to attract electrons

o Electronegativity tends to increase across a periodo As radius decreases, electrons get closer to the bonding atom’s nucleus

o Electronegativity tends to decrease down a group or remain the sameo As radius increases, electrons are farther from the bonding atom’s nucleus

Periodic Table of Electronegativities

Periodic Trend:Electronegativi

ty

Electron Affinity

Definition: the amount of energy released when an electron is added to a neutral atom or molecule in the gaseous state to form a negative ion.

o Electron affinity tends to increase across a periodo The closer to the nobel gases the closer to being happy.

o Electron affinity tends to decrease down a group. If you add electrons as you go down you have more shells and it is farther away from the nucleus.

Periodic Trend:Electron Affinity

Summary of Periodic Trends