Question

An element that never has a positive oxidation state in any of its compound is:
A. Boron
B. Oxygen
C. Chlorine
D. Fluorine

Answer 1

Hint: We know that oxidation state for an atom is the number of electrons that an atom loses or gains to result in a chemical bond.

Complete step-by-step answer:
A. Boron is the element of atomic number 4. Boron is found in Earth having the oxidation state of +3. So, Boron has a positive oxidation state. So, option A is not correct.
B. Oxygen is the element of atomic number 8. Oxygen possesses three oxidation states. In peroxide, oxygen atom exists in -1 oxidation state, that is , in the oxidation state of oxygen is +2 and in all other compounds, the oxidation state of oxygen is -2. So, option B is not correct.
C. Chlorine is one of the non-metal that exists in five oxidation states. The various oxidation states of chlorine in various compounds are -1, +1, +3, +5 and -7. So, a positive oxidation state is exhibited by chlorine. So, option C is incorrect.
Fluorine is the only halogen which exhibits an oxidation state of -1. So, a positive oxidation state is not exhibited by fluorine.

Hence, option D is correct.

Additional Information:
1) If a compound exists in elemental form (only one type of atoms present), the oxidation number of the element is always zero.
2) For ions, the charge indicates the oxidation number. For example, the oxidation number of chloride ions is -1.

Note: Students might think that oxygen possesses oxidation state of -1 and -2 and all the halides possess -1 oxidation state. But it is not correct. All halogens except fluorine exhibit positive oxidation state and oxygen also exhibit oxidation state of +2.