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Where Do The Chemical Elements Come From?

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Where Do The Chemical Elements Come From?

Hydrogen is the most common element in the universe.

The theory of evolution of the stars shows how heavy elements can be formed from lighter ones and it helps to explain the way elements are distributed throughout the universe

        The theory was developed through observation of a range of starts at different stages of their development.

Although hydrogen is the most common element in the universe, its atoms are few and far between, so there is little chance that two hydrogen atoms will come together to form a hydrogen molecule.

There are some regions between stars where molecules do form, these are called dense gas clouds but they aren’t very dense by earth standards The clouds are made up of a mixture of atoms and molecules, mainly hydrogen with a ‘dust’ of solid material from the break up of stars.

The temperature of the clouds varies from 10K to 100K.

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1 H + 21 H 32 He + γ

21 H + 31 H 42 He + 10 n

The nuclear reaction also generate hot wind which drives away some of the dust and gas, leaving behind a new star. This is often surrounded by planets which have condensed out of the remaining dust.

Heavyweight stars

What happens to a star next depends on its mass. The process of nuclear fusion occurs quicker in heavier stars because their centres are denser and therefore hotter. The temperatures get so high that further fusion can occur and make even heavier elements.

Layers of elements form within the star, with the heaviest elements near the centre where it is hottest.

When the core of a heavyweight star contains mainly iron it becomes unstable and explodes. Because when iron nuclei fuse together they absorb energy.

These explosions are called supernovae. As a result of this the elements in the star are dispersed as clouds of dust and gas, and the cycle begins again.

The Sun

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Even further out is the corona here the temp is so high that the atoms have lost many of their electrons.

Emission spectra

When the atoms, molecules and ions around the stars absorb electromagnetic radiation they are raised to higher energy states. The particles can lose their extra energy by emitting radiation. This can be detected on earth.

During a solar eclipse the glow of the suns photosphere id blocked out and we can only detect the light from the chromosphere.

Our Solar system

Our solar system condensed from huge gas clouds with gradually contracted under the force of gravity. As rings of dust and gas condensed around the run, the planets were formed. This material originated from a supernova so contained a range of elements. The non-volatile elements condensed near to the sun (the rocky planets). more volatile elements condensed away from the sun (the giant fluid planets).

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