What is the valency of oxygen in H2O?

Correct option is B

The correct answer is (B) 2

Explanation:
• Valency is the combining capacity of an element. It is determined by the number of electrons in the outermost shell (valence electrons) and how many are needed to complete the octet.
• Oxygen has an atomic number of 8. Its electronic configuration is 2, 6.
• It has 6 electrons in its outermost valence shell. To achieve a stable noble gas configuration (an octet of 8), it needs to gain or share 2 more electrons.
• In a water molecule (H2O), one oxygen atom shares electrons with two hydrogen atoms (each providing 1 electron), forming two single covalent bonds. Thus, its valency is 2.

Information Booster:
• Hydrogen's Valency: Hydrogen has an atomic number of 1. It needs 1 electron to complete its duplet shell (like Helium), so its valency is 1.
• Oxidation State vs Valency: While valency is just a number showing combining capacity without a sign, the oxidation state of oxygen in water is -2, representing the charge it conceptually holds based on electronegativity.

Additional Knowledge:
• Option A (0): Noble gases like Neon or Argon have a valency of 0 because their outermost shells are naturally full.
• Option C (1): Elements in Group 1 (Alkali metals like Sodium) and Group 17 (Halogens like Chlorine) typically have a valency of 1.
• Option D (3): Elements in Group 13 (like Aluminum) or Group 15 (like Nitrogen) typically exhibit a valency of 3.