Final answer:
Nitrogen is the most abundant element in the air with an atomic number of 7, making up about 78% of Earth's atmosphere by volume.
Step-by-step explanation:
The most abundant element in the air with an atomic number of 7 is Nitrogen. Nitrogen forms three chemical bonds and plays a crucial role in the formation of diverse molecular species necessary for life. In contrast to Hydrogen, which is the most common element in the universe, or Oxygen, which is the most abundant on Earth's crust, Nitrogen constitutes the majority of Earth's atmosphere, approximately 78% by volume.
Oxygen, with an atomic number of 8, forms about 20% of the Earth's atmosphere. Carbon and Hydrogen, though abundant in the universe and in compounds on Earth, are not as prevalent in Earth's atmosphere because light gases like Hydrogen can escape into space due to their higher speeds.