Final answer:
The Sun mostly consists of gases, specifically hydrogen and helium, with hydrogen being the most abundant element. Heavier elements make up a smaller percentage of the Sun's mass, and stars vary in composition based on their spectra and the fusion processes taking place in their cores.
Step-by-step explanation:
The Sun is composed mostly of gases, primarily hydrogen and helium. These two elements make up about 99% of the Sun's total mass with hydrogen being the most abundant at roughly 70-75%, followed by helium. The remaining 1-4% consists of heavier elements.
Stars, including our Sun, are analyzed based on their spectra, showing that hydrogen and helium dominate their compositions. The Sun functions through fusion reactions, where hydrogen atoms at the core combine to form helium, releasing enormous amounts of energy. These elements, especially hydrogen, are fundamental to the process that enables stars, including the Sun, to shine and support life on Earth.
In larger stars, the fusion process goes beyond forming helium, creating various other heavier elements like carbon, nitrogen, and even heavier ones like calcium and silicon. The abundance and composition of these heavier elements can vary among different stars, with some older population II stars having much less than what is found in younger, population I stars like the Sun.