Which sample is a pure substance?

Explanation:

Matter is generally classified as either pure or impure substances.

 Pure substances are distinct substances with the following characteristics;

Any substance that is an element or a compound is pure substance.

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.