— periods → rows ⇒ number of electron shells

— groups → columns ⇒ number of valence electrons

— left of zig-zag line → metals

— right of zig-zag line → non-metals

Group I: Alkali Metals

— good conductor of heat and electricity (like all metals)

— a softer metal

— less dense

— lower melting + boiling points ⇒ because metallic bonds = bonds between valence electrons and nucleus ⇒ only one valence electron

Trends

— Li, Na, K, Rb, Cs, Fr

— ↓ density increases

— ↓ softness increases

— ↓ melting points decrease

— ↓ reactivity increases

— reacts vigorously with water, chlorine and oxygen

— reacts similarly because same valence number

— reactive because only has one valence → strong drive to give away and form compounds (ionic)

Group VII: Halogens