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I read somewhere that atoms cannot be created. If this is true, then how did the atoms form after the Big Bang? Also, does this mean that the number of atoms in our universe has remained the same since then? Also, what happens as the universe expands? Does the atoms just scatter or are new atoms being created?

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closed as off-topic by M.A.R. ಠ_ಠ, DSinghvi, bon, Klaus-Dieter Warzecha, buckminst Jan 12 '15 at 19:43

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    $\begingroup$ It looks like your question is rather abot physics and astronomy than chemistry. $\endgroup$ – Mithoron Jan 12 '15 at 14:44
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    $\begingroup$ Simply put atoms are not created or destroyed in chemical reactions, but in nuclear they certainly are. $\endgroup$ – Mithoron Jan 12 '15 at 15:48
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    $\begingroup$ This question appears to be off-topic because it is about astrophysics more than chemistry. It surely can be dealt with better at physics.SE or astronomy.SE. $\endgroup$ – M.A.R. ಠ_ಠ Jan 12 '15 at 16:02
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    $\begingroup$ Historically, in chemistry texts it was common for there to be statements like "All the results of chemistry prove that the ultimate atoms of bodies are unchangeable and imperishable...by no natural process can material atoms be either created or destroyed" Textbook of Chemistry by Draper 1846. So historically the princple that atoms are not created or destroyed has been the foundation of chemistry and the question is relavent to chemistry in that sense, but the details of the answer are nuclear physics and astrophysics. $\endgroup$ – DavePhD Jan 12 '15 at 16:09
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    $\begingroup$ "I have been engaged in experiments which suggest that the atom can be artificially disintegrated. If it is true, it is of far greater importance than a war!" Rutherford, 1917. The belief prevailed long after Dalton. I suppose the relavence to chemistry depends upon how important one considers the history of science to science education. $\endgroup$ – DavePhD Jan 12 '15 at 16:39
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Atoms can be created and destroyed. For example, in nuclear fusion two or more atoms make one atom. In nuclear fission, one atom makes two or more atoms.

how did the atoms form after the Big Bang?

The theory of this process in known as Big Bang Nucleosynthesis

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Starting from protons and neutrons, light elements formed. Later, in stars, nuclei up to iron formed through nuclear fusion. Nuclei heavier than iron formed from supernovae by the r-process and asymptotic branch giant stars by the s-process.

Also, does this mean that the number of atoms in our universe has remained the same since then?

No. The number constantly changes due to fusion, fission, supernovae, creation of neutron stars, black holes and possibily quark stars.

Also, what happens as the universe expands? Does the atoms just scatter or are new atoms being created?

Currently, this process does not create or destroy atoms. However, according to the theory of accelerating expansion, there is a senario referred to as the "big rip" in which all atoms would be destroyed.

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