Group 1: lithium, sodium and potassium

Lithium, sodium and potassium are relatively soft, low-density metals. Their melting points decrease down this sequence, while their reactions with cold water become more vigorous. Low density is a shared property; do not assume density follows a perfectly steady trend.

For sodium: 2Na(s) + 2H₂O(l) -> 2NaOH(aq) + H₂(g). The resulting solution is alkaline because it contains hydroxide ions. The shared outer electron explains the common product pattern. Use observed trends to predict an unfamiliar group-1 element, while treating predicted observations as predictions rather than measured facts.