Question

II. VERY SHORT-ANSWER QUESTIONS
1. Explain why He and H are not considered isotopes.
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Answer 1

Answer:

The atoms of 1,3 hydrogen atom and helium 1,3 atoms are not considered pair of isotopes.An isotopic pair have same atomic number and different mass due to different number of electrons. But in this case the atomic mass is same but atomic number is different.

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Answer 2

Answer:

Because they have same atomic masses but different atomic number.

Explanation:

An isotope have same atomic number and different atomic masses but in this case hydrogen atoms are 1,3 and and helium have 1,3.