<span> the atmosphere holds about 21 per cent oxygen. Over the Earth’s 4.6 billion year history, oxygen did not appear in the atmosphere until perhaps about 2.5 billion years ago. Since then, oxygen levels have fluctuated in tandem with global geological and biological events, such as mass extinctions.</span>
Answer:
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Explanation:
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They become more stable because they achieve a full outer shell of valence electrons with the magic number of 8.
Answer:
There would be three Lithium atoms per one Nitrogen atom.
3:1
Li3N (Lithium Nitride)
Explanation:
Group 15 elements usually have 5 valence electrons, and every atom wants to have a full valence shell of valence electrons. So, nitrogen can get three electrons from each Lithium atom in order to get a full octet.
