Question

The atomic mass of two elements is same. There are 27 protons in first element and 30 protons in second element. If 30 neutrons are present in first element then neutron in second element will be

• A. 27
• B. 30
• C. 29
• D. 28

Answer 1

Answer: (A)

Both element have same atomic mass hence they are isobar. Number of protons in first element =27 Number of protons in second element = 30 Number of neutrons in first element = 30 Atomic mass of first element
= $p+n$
$=27+30$
$=57$
Hence, the atomic mass of second element is also 30. Number of neutrons in second element = atomic mass - number of protons
$=57-30=27$