Earth's atmosphere is primarily composed of which gas?

Earth's atmosphere is primarily composed of which gas?

• A. Oxygen
• B. Nitrogen
• C. Carbon Dioxide
• D. Helium

Answer: (B)

Think about what the air is made of in the largest amounts. In dry air, the most abundant gas is nitrogen, making up roughly three-quarters of the atmosphere. This high abundance comes from nitrogen’s chemical stability, which means it doesn’t react easily and helps keep the atmospheric mix steady. Oxygen is the second most plentiful, but it is not the majority. Carbon dioxide exists only in trace amounts, and helium is present only in tiny quantities. So nitrogen is the primary component of Earth's atmosphere.

Think about what the air is made of in the largest amounts. In dry air, the most abundant gas is nitrogen, making up roughly three-quarters of the atmosphere. This high abundance comes from nitrogen’s chemical stability, which means it doesn’t react easily and helps keep the atmospheric mix steady. Oxygen is the second most plentiful, but it is not the majority. Carbon dioxide exists only in trace amounts, and helium is present only in tiny quantities. So nitrogen is the primary component of Earth's atmosphere.