6.3

the lightest and most abundant element a gas at room temperature a single valence electron in its only shell (can easily gain another e− or lose the one it has, giving it a 1− or 1+ charge) colorless, odorless, tasteless gas diatomic molecule light mass (can move at high speeds and diffuse quickly) reacts like Group 1 and Group 17 elements; therefore, it is in a group by itself can combine with various other elements to form important compounds (halides, hydrocarbons, etc.) can become unstable at high temperatures and pressures

shiny soft solids low densities good conductors (heat, electricity) very chemically reactive have one valence electron which is easily lost form cations with a 1+ charge not found in their pure form difficult to store

denser than Group 1 harder than Group 1 (but still malleable) higher melting points than Group 1 found in the earth and are slightly soluble in water reactive (but less than Group 1) have two valence electrons which are easily lost form cations with a 2+ charge

solids at room temperature (except for mercury a liquid) high density hard; strong shiny good conductors (heat, electricity) ductile; malleable reactivity varies have one or two valence electrons form cations with various charges pure solids in nature (some exceptions)

composed of lanthonoids and actinoids

a group of elements with characteristics that are between those of metals and nonmetals; also known as semiconductors characteristics: shiny luster hardness conductivity chemical reactivity

one metalloid (boron) five post-transition metals have three valence electrons can form cations with a 3+ charge

silvery, metallic luster; easily machined; highly conductive; the most common metal in the earth’s crust

a nonmetal (carbon) two metalloids three metals all: solids at room temperature

nonmetals metalloids post-transition metals all: have five valence electrons; can transfer or acquire electrons as needed

diatomic molecule; colorless, odorless, tasteless gas; 78% of the volume of the earth’s atmosphere

nonmetals one metalloid (two if Polonium is classified as a metalloid) one post-transition metal (depending on Polonium classification) one metal all: have six valence electrons; gain two electrons to form anions with a 2− charge

form salts when they bond with reactive metals are very reactive have seven valence electrons gain an additional electron to form an anion with a 1− charge

colorless, odorless, tasteless extremely low boiling points and freezing points have eight valence electrons (helium has two) have low reactivity highest ionization energies of any group form short-lived, unstable compounds when forced to combine with other elements