In a metallic bond, the free electrons that are responsible for electrical conductivity originate from
- AThe innermost electron shells.
- BThe valence electron cloud.Correct
- CThe interstitial spaces between atoms.
- DThe covalent bond formation.
Solution
Concept
In a metal, outer (valence) electrons are free and form an electron cloud. This cloud carries electric current.
Step-by-step solution
1. In a metallic bond, atoms give their outer (valence) electrons. 2. These electrons are not fixed to one atom. 3. They form a cloud (sea) of free electrons around positive metal ions. 4. When voltage is applied, this cloud moves and gives electrical conductivity. 5. So the free electrons come from the valence electron cloud. Answer is B.
Explanation
In metals, the outer valence electrons become free and move through the whole lattice. This electron cloud holds the ions together and also carries current. Inner shell electrons stay tightly bound to the nucleus.
Why the other options are wrong
A: Inner shell electrons are tightly held by the nucleus, so they are not free. C: Interstitial spaces are empty gaps, they do not produce electrons. D: Covalent bonds share electrons between two atoms, so they are localised, not free.
Shortcut
Metallic bond = sea of valence electrons.
Common mistake
Thinking free electrons come from covalent bonds or from inner shells.
Correct answer: B) The valence electron cloud.