Chapter 20

Metals, Non-metals and Metalloids

Section 2--Nonmetals

• Most of your body’s mass is made of oxygen, carbon, hydrogen and nitrogen

• Calcium makes up the remaining 4% of body mass

• Nonmetals—are elements that usually are gases or brittle solids at room temp.– Usually gases or brittle solids at room

temp– They are not malleable or ductile– They are not good conductors

• All nonmetals except hydrogen are found at the right of the stair-step line.

• Noble gases—group 18—make up the only group of elements that are all nonmetals.

• Most nonmetals can form ionic and covalent compounds

• Hydrogen—90% of Earth’s atoms– Most hydrogen on Earth is part of water– When water breaks down into elements,

hydrogen becomes diatomic

Halogens

• Halogens—Group 17—are very reactive• Form compounds that have many uses

—toothpaste, disinfectants, etc.• If a halogen gains an electron from a

metal, an ionic compound called salt is formed

• In the gaseous state, halogens form reactive diatomic covalent molecules

• Halogens are ID’d by their distinctive colors

Uses of Halogens—check pg. 619

• Noble gases—noble gases exist as isolated atoms

• They are stable because their outermost energy levels are full

• No naturally occurring noble gas compounds are known

• The stability of noble gases makes them useful

• Ex: balloons, neon lights, electric lightbulbs, etc.

Section 3 Notes—Mixed Groups