“…In the first and second short periods, and in the series arsenic -» bromine in the third period, the liquid phase in Groups V, VI, and VII almost vanishes, owing to the formation of very stable molecules in the gaseous state and sometimes also of molecular crystals of the solid. 6. In Groups III B and IV B indium, tin, thallium, and lead have low melting points, owing to incomplete ionization in the solid state, as shown by the interatomic distances.…”