7. which main group in the periodic table of elements contains only nonmetals?

a. 1a
b. 6a
c. 8a
d. 2a

C. 8A

Explanation:

Elements in the periodic table are classified as either metal, non-metals or metalloids. Metals are elements in the periodic table that are characterized by being good conductors of heat and electricity. Additionally, they react by forming cations to attain an octet configuration.Examples are elements in groups 1A. 2A, 3A and transition metals.Non-metals are elements that react by forming anions to attain an octet configuration. They are characterized by being poor conductors of heat and electricity and mostly exist as gases or liquids.Examples are elements in group 6A, 7A, and 8A. However, group 6A contains non-metals and a metal element polonium, unlike group 8A which only contains non-metals.Metalloids, on the other hand, are elements that have both the characteristics of metals and non-metals.

1.from liquid state to gaseous state is evaporation 3.solid to liquid is melting 5. solid to gaseous state is sublimation 6. gas to solid state is decomposition 7. a change of state is known as the states of matters