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Q27 (CDS-II/2016) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Basic chemical principles Answer Verified

Which one of the following statements is correct?

Result
Your answer: —  Â·  Correct: D
Explanation

Hydrogen exhibits multiple oxidation states depending on its chemical environment. In its elemental form, such as the H2 molecule, the oxidation number of hydrogen is 0. When hydrogen combines with more electronegative non-metals (e.g., in H2O or HCl), it typically assumes an oxidation state of +1. However, when it reacts with less electronegative elements like alkali or alkaline earth metals to form metal hydrides (e.g., NaH or CaH2), it acts as a hydride ion (H-) with an oxidation state of -1 [2]. This variability is due to hydrogen's unique position and electronegativity, allowing it to either lose, gain, or share electrons to fill its 1s shell. Consequently, statements claiming its oxidation number is 'always' a single value are incorrect, making the fourth option the only accurate description.

Sources

  1. [1] Science , class X (NCERT 2025 ed.) > Chapter 4: Carbon and its Compounds > 4.1 BONDING IN CARBON – THE COVALENT BOND > p. 59
  2. [2] Science , class X (NCERT 2025 ed.) > Chapter 3: Metals and Non-metals > What you have learnt > p. 56
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SIMILAR QUESTIONS

NDA-I · 2014 · Q45 Relevance score: 5.76

Which of the following statements about hydrogen is /are correct? 1. Hydrogen has three isotopes of which protium is the most common. 2. Hydrogen ion (H+) exists freely in solution. 3. Dihydrogen, H2, acts as a reducing agent. Select the correct answer using the code given below.

NDA-I · 2012 · Q19 Relevance score: 5.47

Which of the following statements regarding oxidation and reduction are correct? 1. In oxidation, loss of electron takes place whereas in reduction, gain of electron takes place. 2. In oxidation, gain of electron takes place whereas in reduction, loss of electron takes place. 3. Oxidizing agent decreases the oxidation number but reducing agent increases the oxidation number. 4. Oxidizing agent increases the oxidation number but reducing agent reduces the oxidation number. Select the correct answer using the code given below ; Code:

NDA-I · 2025 · Q83 Relevance score: 5.12

Which one of the following statements regarding oxidation and reduction reactions is NOT correct ?