— 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
— 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
— 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)