Question

A neutral atom of an element with nuclear charge $11$ times and mass $23$ times that of hydrogen. Find the ratio of electrons to protons present in its stable ion.
A. $1:1$
B. $5:6$
C. $10:11$
D. $12:11$

Answer 1

Hint : We know that an atom consists of the three subatomic particles. These subatomic particles are protons, electrons and neutrons. Most of the mass of the atom is in its nucleus in a small dense area at the centre of the atom. All the positive charge of the atom remains in the nucleus. Electrons are negatively charged particles which are located outside of the nucleus.

Complete step by step solution:
> We can define a neutral atom as an atom which has an equal number of positive and negative particles. That means a neutral atom has an equal number of electrons and protons hence the number of electrons is equal to the atomic number. It is given in the problem statement that a neutral atom of an element with nuclear charge $11$ times and mass $23$ times that of hydrogen. Hence we know that in this condition protons in the neutral atom will be equal to the electrons in the atom.
> Number of protons in the neutral atom= nuclear charge= electrons in the neutral atom $ = 11$
> Mass of the neutral atom $ = 23$ Thus the element is sodium. Its stable ion is $N{a^ + }$ which is formed by the loss of one electron. So the number of electrons in its stable ion $ = 11 - 1 = 10$and Number of protons in the stable ion $ = 11$ . Hence the ratio of electron to proton in sodium ion will be $10:11$. Thus option C is the correct answer to this problem.

Note : We have approached this problem with the help of the concept of atomic structure where we have learned about neutral atoms that contain the same number of protons and electrons. Every atom tries to be in a stable state by donation or acceptance of electrons. Here the sodium atom donates an electron and forms a stable ion $N{a^ + }$.