Question

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

Answer 1

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

Step-by-step explanation:

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

Atomic number of At(astatine ) =85

That means it has --- 85protons.

Its mass number A=210

Hence, the number of neutrons in At are:

`n=A-Z\\=>n=210-85\\=>n=125`

Second option:

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