Periodic Table Trends

Atomic Radius

The distance from the center of an atom's nucleus to its outermost orbital.

Ionic Radius

The radius of an atom after becoming an ion by losing or gaining electrons.

Ionization Energy

The amount of energy an isolated gaseous atom must absorb to lose its outermost valence electron.

Electronegativity

An atom's ability to attract shared electrons toward itself to form a chemical bond.

Electron Affinity

The change in energy in a neutral gaseous atom when an electron is added to make a negative ion.

Effective Nuclear Charge

The attraction or pull an electron feels from the nucleus of an atom.

Coulomb's Law

The attraction between oppositely charged particles is directly related to the amount of charge and inversely proportional to the distance between them.

Atomic Radius Trend Down a Group

Generally increases.

Atomic Radius Trend Across a Period

Generally decreases from left to right.

Ionic Radius Trend Down a Group

Generally increases.

Ionic Radius Trend Across a Period

Generally decreases from left to right, then jumps at the nonmetals.

Ionization Energy Trend Down a Group

Generally decreases.

Ionization Energy Trend Across a Period

Generally increases from left to right.

Electronegativity Trend Down a Group

Generally decreases. Excludes noble gases.

Electronegativity Trend Across a Period

Generally increases from left to right. Excludes noble gases.

Electron Affinity Trend Down a Group

Generally decreases. Excludes noble gases.

Electron Affinity Trend Across a Period

Generally increases from left to right. Excludes noble gases.

Why do elements in the same family have similar properties?

They have the same number of valence electrons.

Why does atomic radius increase down a group?

According to Coulomb's Law, electrons farther from the nucleus are less attracted to it, making the atom larger.

Why does atomic radius decrease across a period?

Effective nuclear charge increases from left to right, causing a stronger pull on electrons and decreasing atomic size.

Which trends exclude noble gases?

Electronegativity and electron affinity.

Why are noble gases excluded from electronegativity and electron affinity trends?

They generally do not want additional electrons.

What happens to atomic radius as you move down a group?

It increases.

What happens to atomic radius as you move left to right across a period?

It decreases.

What happens to ionization energy as you move down a group?

It decreases.

What happens to ionization energy as you move left to right across a period?

It increases.

What happens to electronegativity as you move down a group?

It decreases.

What happens to electronegativity as you move left to right across a period?

It increases.

What happens to electron affinity as you move down a group?

It decreases.

What happens to electron affinity as you move left to right across a period?

It increases.