NONMETALS AND METALLOIDS

What is a nonmetal?

Elements that lack most of the properties of metals.

Located to the right of the zigzag line in the periodic table.

Very common elements Extremely important to all living things

on Earth

Physical Properties

Many are gases at room temperature Opposite to those that characterize the

metals Dull Break apart or easily crumble into pieces. Poor conductors of heat and electricity

Chemical Properties

Readily form compounds; however, group 18 rarely ever do

Compounds of Nonmetals

When nonmetals and metals react – valence electrons move from the metal atom to the nonmetal atom. Na + Cl = NaCl

Nonmetals can form compounds with other nonmetals too. Atoms share electrons Many even form molecules of two identical

atoms – diatomic molecules (O₂ , N₂, H₂)

Families of Nonmetals

Carbon Family Nitrogen Family Oxygen Family Halogen Family Noble Gases Hydrogen

Carbon Family

Group 14 Each element has atoms with 4 valence

electrons Only one element is a nonmetal – Carbon Two are metalloids – silicon and

germanium Two are metals – tin and lead

Nitrogen Family

Group 15 Contain 5 valence electrons Two nonmetals – nitrogen and

phosphorus

Oxygen Family

Group 16 Six valence electrons Three nonmetals – oxygen, sulfur,

selenium The oxygen we read is a diatomic

molecule Ozone is a triatomic molecule Oxygen is very reactive and can

combine with almost any element.

Halogen Family

Group 17 Fluorine, chlorine, bromine, iodine and

astatine All are nonmetals except astatine 7 valence electrons All are very reactive, most are

dangerous to humans

Noble Gases

Group 18 Do not ordinarily form compounds with

other elements Do not gain, lose or share their valence

electrons Generally very stable and unreactive All exist in Earth’s atmosphere in small

amounts

Hydrogen

Hydrogen has chemical properties very different from other elements in family.

Makes up more that 90% of the atoms in the universe

1% of mass of Earth’s crust, oceans, and atmosphere

Rarely found on Earth as a pure element

Metalloids

Have some of the characteristics of metals and some of nonmetals

Seven metalloids Most common is silicon Most useful property is their varying

ability to conduct electricity. Some are used to make semiconductors