How old is the sun and since its birth, how has the sun changed?

The present age of the Sun is 4.6 billion years old. It will live for about 5.4 billion years more. Initially, the Sun was majorly composed of Hydrogen. Current composition of the Sun is 70% hydrogen, 28% Helium and 2% heavier elements. Thus, the composition has changed since birth due to nuclear fusion process in the core.

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explanation:

each principal energy level above the first contains one s orbital and three p orbitals. a set of three p orbitals, called the p sublevel, can hold a maximum of six electrons. therefore, the second level can contain a maximum of eight electrons - that is, two in the s orbital and 6 in the three p orbitals.

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