Question

The total number of electrons, protons and neutrons present in the three isotopes of hydrogen is

• A. 3
• B. 5
• C. 6
• D. 9

Hint:

When counting subatomic particles, remember that isotopes differ only in neutron count; the proton and electron counts remain constant for all neutral isotopes of the same element.

Answer 1

The Correct Option is D

Step 1: Recall the three hydrogen isotopes.
They are protium $^1H$, deuterium $^2H$ and tritium $^3H$. They all have 1 proton and 1 electron but different numbers of neutrons.
Step 2: Count particles in protium.
1 proton, 1 electron, and neutrons $=1-1=0$. Total $=1+1+0=2$.
Step 3: Count particles in deuterium.
1 proton, 1 electron, and neutrons $=2-1=1$. Total $=1+1+1=3$.
Step 4: Count particles in tritium.
1 proton, 1 electron, and neutrons $=3-1=2$. Total $=1+1+2=4$.
Step 5: Add all three totals.
\[ 2+3+4=9 \]
Step 6: State the answer.
So all electrons, protons and neutrons across the three isotopes add to 9. \[ \boxed{9} \]