Periodic Table Trends and Properties: Atomic Size, Ionization, Electronegativity

Periodicity

Repeating pattern of properties across periods and groups.

Periods

Horizontal rows in the periodic table, arranged from left to right.

Groups

Vertical columns in the periodic table, arranged from top to bottom.

Periodic Law

Principle that when elements are arranged by increasing atomic number, their physical and chemical properties show a repeating pattern.

Ionization Energy

Amount of energy required to remove an electron from an atom or ion in the gaseous state.

Ionization Energy Trend

Increases across a period and decreases down a group.

First Ionization Energy (IE₁)

Energy needed to remove the first electron from a neutral atom.

Second Ionization Energy (IE₂)

Energy required to remove a second electron from the +1 ion.

Third Ionization Energy (IE₃)

Energy needed to remove a third electron from the +2 ion.

Atomic Radius

Distance from the nucleus to the outer electron.

Atomic Radius Trend

Decreases across a period and increases down a group.

Cations

Ions that are smaller than their neutral atoms.

Anions

Ions that are larger than their neutral atoms.

Halogens

Reactive nonmetals located in Group 17.

Alkali Metals

Very reactive, soft metals located in Group 1.

Alkaline Earth Metals

Reactive metals, less reactive than Group 1, located in Group 2.

Metalloids

Elements with mixed properties located on the 'staircase' of the periodic table.

Noble Gases

Colorless, odorless, nonmetallic elements located in Group 18.

Effective Nuclear Charge

Net positive charge felt by outer electrons.

Electron Affinity

Amount of energy released or absorbed when an atom gains an electron to form an anion.

Electronegativity

Tendency of an atom to attract electrons toward itself in a chemical bond.

Electronegativity Trend

Increases across a period and decreases down a group.

Ionic Trends

Trends in size and properties of ions formed from atoms.

Cation Formation

Cations are formed by losing electrons, usually metals.

Anion Formation

Anions are formed by gaining electrons, usually nonmetals.

General Periodic Trends

Metals tend to form cations and nonmetals tend to form anions.