Question

The ratio of the neutrons present in the nitrogen atom and a silicon atom is-
(Mass number of nitrogen and silicon is $14$ and $28$ respectively)
A.$7:3$
B.$3:7$
C.$1:2$
D.$2:1$

Answer 1

Atomic number of atom is equal to the number of protons present in the atom and Mass number is the sum of number of protons and number of neutrons in an atom. Hence we can use the following formula to find the number of neutrons -
The number of neutrons=Mass number-Atomic number
Then take the ratio to get the answer.

Complete step by step answer:
Given, the mass number of nitrogen is $14$
And the mass number of silicon is $28$.
We have to find the ratio of neutrons present in nitrogen atoms and a silicon atom.
Mass number of an atom is the number of protons and neutrons combined. The number of protons is always equal to the number of electrons in all atoms of an element but the number of neutrons varies.
And we know that atomic number of an atom=the protons present in an atom
So we can write,
The number of neutrons=Mass number-Atomic number-- (i)
For nitrogen,
Atomic number=$7$ and mass number=$14$
Then on using the formula (i) and putting the given values, we get-
Number of neutrons in nitrogen=$14 - 7$
On subtracting we get,
Number of neutrons in nitrogen=$7$
For silicon,
Atomic number=$14$ and mass number=$28$
Then on using the formula (i) and putting the given values, we get-
Number of neutrons in silicon=$28 - 14$
On subtracting we get,
Number of neutrons in silicon=$14$
Now the ratio of neutrons present in nitrogen and silicon atom is=$\dfrac{{{\text{Number of neutrons in nitrogen}}}}{{{\text{Number of neutrons in silicon}}}}$
On putting values we get,
Ratio=$\dfrac{7}{{14}} = \dfrac{1}{2}$
So the ratio of neutrons present in nitrogen and silicon is $1:2$

Hence, the correct option is C.

Note:
Neutron was discovered by James Chadwick in the year $1932$ and in $1935$, he was awarded the Nobel prize in physics for this discovery. Neutron has following properties-
-It is considered a neutral particle which means it has zero charge.
-Neutrons are affected by the presence of magnetic fields but are not affected by electric field.
-Neutrons play a very important role in nuclear reactions as they induce radiation.