Melting point and boiling point

The melting point and boiling point are measures of the attractive forces between atoms or molecules. Elements, such as metals, that have strong attractive forces have higher melting points and boiling points than nonmetals, which have very weak forces of attraction.

Periodic Trend

Halogens

The physical states of the halogens at room temperature varies from gas to liquid to solid as one moves down the group. As a result, the melting points and boiling points increase as one moves down the group.

Halogens	Melting Point (K)	Boiling Point (K)	Physical State at Room Temperature
Fluorine	53	85	Gas
Chlorine	173	239	Gas
Bromine	266	332	Liquid
Iodine	387	458	Solid

Alkali Metals

The alkali metals show a decrease in melting points and boiling points due to the weaker metallic bonds between atoms as their size increase down the group.

Alkali Metals	Melting Point (K)	Boiling Point (K)	Physical State at Room Temperature
Lithium	454	1615	Solid
Sodium	371	1156	Solid
Potassium	336	1032	Solid
Rubidium	312	961	Solid
Cesium	301	944	Solid

Content suitability

BCIT courses: CHEM 0011