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Astatine is a halogen with several isotopes that all have short half-lives. Which of the following combinations of mass number and neutrons are possible as isotopes of astatine? Choose one or more:
i) A = 211, n = 127
ii) A = 210, n = 125
iii) A = 220, n = 134
iv) A = 207, n = 122
v) A = 209, n = 124

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Answer:

Astatine is a halogen with several isotopes that all have short half-lives.

Which of the following combinations of mass number and neutrons are possible as isotopes of astatine? Choose one or more:

i) A = 211, n = 127

ii) A = 210, n = 125

iii) A = 220, n = 134

iv) A = 207, n = 122

v) A = 209, n = 124

Explanation:

The mass number is the sum of the number of protons and the number of neutrons in an atom.[tex]A=no.of protons+no.of neutrons\\=>no.of neutrons=A-no.of protons\\[/tex]

Atomic number of At(astatine ) =85

That means it has --- 85protons.

Its mass number A=210

Hence, the number of neutrons in At are:

[tex]n=A-Z\\=>n=210-85\\=>n=125[/tex]

Second option:

ii) A=210 , n=125 is the answer.

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