What is the first element of the periodic table, also the most abundant element in the universe?

• A. Hydrogen
• B. Helium
• C. Oxygen
• D. Nitrogen

Answer: (A)

Hydrogen fits both ideas being tested: it is the element with atomic number one, and it is the most abundant element in the universe. It’s the simplest atom, with one proton and one electron, and it formed in the early moments after the Big Bang. Because of that origin, hydrogen remains the main building block of stars and the gas that fills much of the cosmos. In the universe, about three-quarters of ordinary matter is hydrogen, with helium making up most of the rest and heavier elements like oxygen and nitrogen contributing only a small fraction. So hydrogen is the best answer because it is first on the periodic table and overwhelmingly the most abundant element in the cosmos.