<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>
<u>Answer:</u> The energy released in the given nuclear reaction is 1.3106 MeV.
<u>Explanation:</u>
For the given nuclear reaction:
We are given:
Mass of 
= 39.963998 u
Mass of 
= 39.962591 u
To calculate the mass defect, we use the equation:
Putting values in above equation, we get:
To calculate the energy released, we use the equation:
(Conversion factor: 
)
Hence, the energy released in the given nuclear reaction is 1.3106 MeV.
Answer:
The combination of nuclei to form a bigger and heavier nucleus is known as Fussion. The consequence of fusion is the absorption or release of energy.
Explanation: Sodium is a metal with a low electronegativity it will form an ionic bond with a non metal with a high electronegativity.
Both Florine and Sulfur are non metals with high electronegativity.
Neon is a noble gas family VIII A and normally doesn't form any bonds at all.
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Water flows under the ground
