#5 Sodium is a metal and sulfur is a non-metal....why we classify them this way??
Physical properties
Metal conduct electricity well while non-metal is a poor conductor of electricity

Chemical properties
Sodium (2.8.1) is a metal because it will lose 1 electron to complete the valence shell.
Sulfur (2.8.6) is a non-metal because it will gain 2 electrons to complete the valence shell