Question

1. use electron dot diagrams to represent the sharing of electrons in one molecule of each of the following substances: (a) water, h₂o (b) oxygen, o₂ (c) nitrogen, n₂ (d) carbon dioxide, co₂ (e) methane, ch₄ (f) hydrogen bromide, hbr

Explanation:

Step1: Determine valence electrons

For water ($H_2O$), oxygen has 6 valence electrons and each hydrogen has 1 valence - electron. For oxygen ($O_2$), each oxygen atom has 6 valence electrons. For nitrogen ($N_2$), each nitrogen atom has 5 valence electrons. For carbon dioxide ($CO_2$), carbon has 4 valence electrons and each oxygen has 6 valence electrons. For methane ($CH_4$), carbon has 4 valence electrons and each hydrogen has 1 valence electron. For hydrogen bromide ($HBr$), hydrogen has 1 valence electron and bromine has 7 valence electrons.

Step2: Draw electron - dot diagrams

(a) Water ($H_2O$)

Oxygen is the central atom. It shares one electron with each hydrogen atom. The electron - dot diagram shows oxygen with 4 non - bonding electrons (2 lone pairs) and 2 bonding pairs (shared with hydrogen atoms).

(b) Oxygen ($O_2$)

Each oxygen atom shares 2 electrons with the other oxygen atom to form a double bond. Each oxygen also has 2 lone pairs of electrons.

(c) Nitrogen ($N_2$)

Each nitrogen atom shares 3 electrons with the other nitrogen atom to form a triple bond. Each nitrogen also has 1 lone pair of electrons.

(d) Carbon dioxide ($CO_2$)

Carbon is the central atom. It shares 2 pairs of electrons with each oxygen atom, forming two double bonds. Each oxygen has 2 lone pairs of electrons.

(e) Methane ($CH_4$)

Carbon is the central atom. It shares 1 electron with each of the 4 hydrogen atoms.

(f) Hydrogen bromide ($HBr$)

Hydrogen shares 1 electron with bromine. Bromine has 3 lone pairs of electrons.

Answer:

(a) For $H_2O$: O is central, with two H atoms bonded to it. O has 2 lone pairs.
(b) For $O_2$: Two O atoms with a double - bond between them and 2 lone pairs on each O.
(c) For $N_2$: Two N atoms with a triple - bond between them and 1 lone pair on each N.
(d) For $CO_2$: C is central, with two double - bonds to two O atoms. Each O has 2 lone pairs.
(e) For $CH_4$: C is central, with single bonds to 4 H atoms.
(f) For $HBr$: H and Br with a single bond, and Br has 3 lone pairs.