| A | B |
|---|
| alkali metals | most reactive; soft; one valence electron |
| alkaline earth metals | hard; very reactive; two valence electrons |
| transition metals | good conductors; react slowly with air and water |
| lanthanides | part of period 6; form alloys |
| actinides | part of period 7; radioactive; artificially made |
| halogens | nonmetals; dangerous to humans; seven valence electrons |
| noble gases | rarely form compounds; eight valence electrons |
| hydrogen | lightest, simplest element; flammable |
| sodium, potassium, calcium | important to people's diets |
| lithium | used in batteries |
| uranium | used as nuclear fuel |
| aluminum | used to make cans and airplane parts |
| silicon & germanium | used as semiconductors |
| carbon | found in all living things; forms proteins, fats, & carbohydrates |
| tin | used to coat steel cans |
| nitrogen | 80% of the air; used to make fertilizers |
| oxygen | animals breathe it; one kind protects earth from UV rays |
| fluorine | nonstick cookware; prevents tooth decay |
| chlorine | disinfects; a part of salt (NaCl) |
| helium | used in balloons and blimps |
| neon | glows orange in signs |
| hydrogen | 90% of atoms in the universe; part of water; make up stars |
