What is the mass of Potassium in 5.2g of KBr?

14.5%.

Explanation:

The idea here is that you need to determine how many grams of potassium bromide will be present for every 100. g of this is.

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.