Answer : The correct option is, (A) 10
Explanation :
Atomic number : It is defined as the number of protons or number of electrons. That means,
Atomic number = number of protons = number of electrons
Atomic mass : It is defined as the sum of number of protons and number of neutrons.
Atomic mass = Number of neutrons + Number of protons
As we are given that,
The atomic number of an element = 10
The atomic mass of an element = 20
Now we have to determine the number of neutrons.
Atomic number = number of protons = 10
Atomic mass = Number of neutrons + Number of protons
Number of neutrons = Atomic mass - Number of protons
Number of neutrons = 20 - 10 = 10
Therefore, the number of neutrons are, 10
