Periodic Table

Periodic Law

The principle that chemical and physical properties of elements recur periodically when arranged by atomic weights or atomic numbers.

Periods

The rows in the periodic table that indicate the number of energy shells in elements.

Similar Properties

Every element in the periodic table shares similar properties with others in the same group.

Atomic Number

The number of protons in an element's nucleus, which determines the arrangement of the periodic table.

Number of Periods

There are 7 periods in the periodic table.

Main Elements (A)

One of the two groups in the periodic table, where the number of valence electrons is more predictable.

Transitional Elements (B)

The second group in the periodic table, where the number of valence electrons is less predictable.

Valence Electrons

The electrons in the outermost shell of an atom, which determine its chemical properties.

Column/Group

The vertical sections of the periodic table that indicate the number of valence electrons.

Row/Period

The horizontal sections of the periodic table that indicate the number of energy shells.

Alkali Metals

A family in the periodic table known for being highly reactive and having one valence electron.

Alkaline Earth Metals

A family in the periodic table characterized by having two valence electrons and moderate reactivity.

Metals

Elements that are typically good conductors of heat and electricity, found on the left side of the periodic table.

Nonmetals

Elements that are generally poor conductors of heat and electricity, found on the right side of the periodic table.

Metalloids

Elements that have properties intermediate between metals and nonmetals.

Inner Transition Metals

A group of elements that includes the lanthanides and actinides, typically found at the bottom of the periodic table.

Noble Gases

A family of elements known for their lack of reactivity due to having a full valence shell.