Which of the following is a molecular compound?
D KI
D CC14
NaBr
0 MgCl2

it is NaBr. It is known as sodium bromide.

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.

b. examine and describe cells