Question

The charge on an electron is \[4.8 \times {10^{ - 10}}\] esu. What is the value of charge on \[L{i^ + }\] ion?
A. \[4.8 \times {10^{ - 10}}\] esu
 B.\[9.6 \times {10^{ - 10}}\] esu
 C.\[1.44 \times {10^{ - 9}}\] esu
 D.\[2.4 \times {10^{ - 10}}\] esu

Answer 1

Hint: An atom has protons in its nucleus and electrons revolving around the nucleus. The charge on an electron is equal and opposite to that of a proton or vice versa i.e. the charge only differs by sign. Due to this reason, the charges cancel out each other and we get a neutral atom. But in case of ions, we get some charge on it equal to the value of electron and proton and respective charge.

Complete step-by-step answer:
We know that an atom has protons and neutrons in its nucleus, known as nucleons. There are electrons revolving around the nucleus which have a negative charge whereas protons have positive charge. The charge on an electron is equal and opposite to that of a proton or vice versa. It only differs by sign i.e. positive for proton and negative for electron.
Due to this reason, the charges cancel out each other because they are equal and opposite and we get a neutral atom. But in case of ions such as cation or anion, the atom either loses electrons or gains electrons. If it gains an electron, we call it cation and if it loses electrons, we call it an anion.
So, we get some charge on it which can be either positive when it is a cation or negative when it is an anion. In such cases, we see that the charge gets imbalanced on the atom and we lose its neutrality.
We are given \[L{i^ + }\] ion and we know that lithium atoms have atomic number three. This implies that it has three protons in its nucleus and three electrons revolving around the nucleus. But when it loses an electron, it becomes a cation. On losing an electron, three protons and two electrons are left behind in the atom. The charge on two protons gets balanced by charge on two electrons but one proton is still there with its charge as there is no electron to balance it.
Therefore, the charge on \[L{i^ + }\] ion will be equal to the charge of proton. Since charge of a proton is equal to charge of an electron , we are given that the charge on an electron is \[4.8 \times {10^{ - 10}}\] esu, so this is equal to the charge on a proton with a positive sign. Thus, we get the value of charge on \[L{i^ + }\] ion as
 \[ + 4.8 \times {10^{ - 10}}\] esu
Hence, the correct option is (A).

Note: It is not possible to form an ion such as cation or anion by removing a proton from the nucleus and thus possessing a net negative charge. Cations are smaller in size as compared to anions. In general, metals form cations and nonmetals form anions as per their electronic configuration.