Milady Esthetics State Board Practice Test

What is the lightest element known?

1. Carbon

2. Oxygen

3. Hydrogen

4. Helium

The correct answer is: Hydrogen

Hydrogen is recognized as the lightest element known, with an atomic number of one. This means that it has only one proton in its nucleus, making it the simplest and least massive of all the elements. In its natural state, hydrogen is a gas composed of diatomic molecules (H2), and because of its low atomic weight, it plays a crucial role in numerous chemical reactions and is essential for the formation of water and organic compounds. Carbon, oxygen, and helium are all heavier than hydrogen. Carbon, for example, has an atomic number of six, indicating a significantly larger mass due to the addition of five more protons. Oxygen comes with an atomic number of eight, and helium, although light compared to many other elements, has an atomic number of two, which makes it heavier than hydrogen. Understanding the relative weights and atomic structures of these elements highlights why hydrogen is classified as the lightest element.