Explain why hydrogen is a light gas whilst iron is a heavy solid ?

Due to the atomic mass, different for every element, hydrogen is the lightest element and it's a gas at room temperature due to its properties like point of  ebollition. iron is a heavy solid because it has a high atomic mass and a high point of fusion(temperature needed to melt it).

The Sun is the major source of energy

pls mark brainliest. thank you