Oxidation number of sodium in sodium amalgam is: (A) +2 (B)+1 (0-2 (D) zero

Key Concepts to Recall

1. Oxidation Number (O.N.)
   • It is a bookkeeping tool that tells us how many electrons an atom has gained or lost formally in a compound.
   • Element in its native or elemental form always has $\text{O.N.} = 0$.

2. Amalgam
   • An amalgam is an alloy of mercury with another metal.
   • In alloys, metals are mixed physically; they are not present as ions that have transferred electrons completely.
   • Hence, each metal behaves like the free element inside the alloy.

Logical Chain a Student Should Follow

1. Identify the Chemical Environment — Sodium amalgam is an alloy (a physical mixture) and not an ionic compound.
2. Recall the Rule — Elements in their elemental/metallic state carry an oxidation number of zero.
3. Apply the Rule — Since sodium hasn’t donated or accepted electrons formally inside the amalgam, assign $0$ to its oxidation number.
4. Select the Option — Choose the option that says zero.

Imagine a Friend Group

Think of sodium (Na) and mercury (Hg) as two friends playing together in a playground. When sodium is alone, it can give away one of its toys (an electron) and become Na⁺. But in a sodium-mercury mix (called an amalgam), sodium does not give away or take any toys. They are just standing side-by-side, still holding their own toys.

Because sodium hasn’t lost or gained any toy (electron), we say its score (oxidation number) is zero.

Step-by-Step Calculation

1. Recognise Nature of Substance
   Sodium amalgam is an alloy, not an ionic compound.

2. Apply Oxidation Number Rule for Elements
   In an alloy, each metallic element is essentially in its elemental form. Therefore,

   $\text{Oxidation number of Na in Na–Hg amalgam} = 0$

3. Choose the Correct Option
   • Option (D) zero is the right answer.

[ \boxed{\text{Option (D): zero}} ]