Question

The numbers of protons, electrons and neutrons in a molecule of heavy water are respectively:

• A. 8, 10, 11
• B. 10, 10, 10
• C. 10, 11, 10
• D. 11, 10, 10

Answer 1

The correct option is B 10, 10, 10

Heavy water is $D_{2}O$
Deuterium contains 1 proton, 1 neutron and 1 electron.
Oxygen contains 8 protons, 8 neutrons and 8 electrons.

Hence, for $D_{2}O$
Number of electrons =2+8=10
Number of protons =10
Molecular mass of $D_{2}O$ =4+16=20
hence,
$\text{Number of neutron = Molecular mass - number of protons}$
$=20-10=10$

Hence, option (b) is correct.