Why are chondrites chemically similar to the Sun except for volatile elements?

Chondrites are considered primitive, largely chemically unaltered samples of the early solar system. Because the Sun contains the vast majority of the solar system's mass, its composition is representative of the initial material from which the solar system formed.12

Chondrites, particularly the CI carbonaceous chondrites, are chemically similar to the Sun because they are composed of the original dust and mineral grains that condensed out of the cooling solar nebula. These meteorites represent the building blocks of planets, having aggregated from solid material before significant planetary differentiation occurred.12

The discrepancy regarding volatile elements—such as hydrogen and helium—exists because these substances have low freezing temperatures. In the warmer regions of the inner solar system where these meteorites formed, volatile substances could not condense into solid form and were therefore not retained in the solid grains that accreted to form chondrites. Consequently, while chondrites match the Sun's nonvolatile elemental abundances, they lack the light, gaseous elements that remained in the nebular gas or were only retained in the colder, outer reaches of the solar system.132