Question

An atom consists of charged particles called electrons and protons. Each proton has a charge of +1 and each electron has a charge of –1. Remember number of electrons is equal to number of protons, while answering these questions:

1. What is the charge on an atom?
2. What will be the charge on an atom if it loses an electron?
3. What will be the charge on an atom if it gains an electron?

Answer 1

a. Let a be the number of electrons in an atom.

Number of protons in the atom, will also be equal to a.

Since, an atom has equal number of protons and electrons.

∴ Charge on one electron = (–1)

∴ Total charge in a electrons = a × (–1) = –a

∴ Charge on one proton = (+1)

∴ Total charge in a protons = a × (+1) = + a

Hence, total charge on the atom = Charge of electrons + Charge of protons

= –a + a

= 0

b. If an atom loses an electron, it will have (a – 1) electrons and a protons.

∴ Charge in one electron = (–1)

∵ Charge in (a – 1) electrons = (a – 1) × (–1) = – (a – 1) = (1 – a)

∴ Charge in one proton = (+1)

∵ Charge in a protons = (+1) × a = (+a)

Hence, total charge on the atom = Charge of electrons + Charge of protons

= 1 – a + a

= + 1

c. If an atom gains an electron, it will have (a + 1) electrons and a protons

∴ Charge in one electron = –1

∴ Charge in (a + 1) electrons = –1 × (a + 1) = –(a + 1)

∴ Charge in one proton = (+1)

∴ Charge in a protons = (+1) × a = (+ a)

Hence, total charge on the atom = Charge of electrons + Charge of protons

= a – (a + 1)

= (–1)