A pure substance is one that a. Has been filtered
b. is an element or compound
c. If found in nature
d. Has been cleaned

sodium (na), for example, has one electron in its valence shell. this is an unstable state because that valence shell needs eight electrons to be full. in order to fill its valence shell, find a way to add seven electrons to its valence shell

d.) the average kinetic energy of the gas particles is greater in container b because its particles move faster.

oxygen, selenium, tellurium, and polonium.

they're all from the same group as sulfur (group 16).

elements make up everything, and they combine to make compounds.

the answer is c