Use covalent Lewis structures to explain why the compound that forms between nitrogen and hydrogen has the formula NH3 and why NH2 and NH4 are not stable.

Name: Chemistry: A Molecular Approach
Author: Tro
ISBN: 9780137832217

Verified step by step guidance

insert step 1> Identify the valence electrons for nitrogen and hydrogen. Nitrogen has 5 valence electrons, and hydrogen has 1 valence electron.

insert step 2> Determine the total number of valence electrons available for bonding in NH3. Nitrogen contributes 5 electrons, and each hydrogen contributes 1 electron, totaling 8 valence electrons.

insert step 3> Draw the Lewis structure for NH3. Place nitrogen in the center and arrange three hydrogen atoms around it. Use pairs of electrons to form single bonds between nitrogen and each hydrogen.

insert step 4> Check the stability of NH3 by ensuring that nitrogen has a complete octet (8 electrons) and each hydrogen has a complete duet (2 electrons).

insert step 5> Explain why NH2 and NH4 are not stable. NH2 would leave nitrogen with an incomplete octet, and NH4 would require nitrogen to have 9 electrons, exceeding the octet rule.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Covalent Bonding

Covalent bonding occurs when two atoms share pairs of electrons to achieve a full outer shell, leading to greater stability. In the case of nitrogen and hydrogen, nitrogen has five valence electrons and needs three more to complete its octet, while each hydrogen atom has one electron. By sharing electrons, nitrogen can form three covalent bonds with three hydrogen atoms, resulting in the stable molecule NH3 (ammonia).

Lewis Structures

Lewis structures are diagrams that represent the bonding between atoms and the lone pairs of electrons in a molecule. They help visualize how atoms share electrons to form covalent bonds. For NH3, the Lewis structure shows nitrogen at the center with three hydrogen atoms bonded to it and one lone pair of electrons, indicating a stable arrangement. In contrast, NH2 (hydrazine) lacks a full octet for nitrogen, making it less stable.

Stability of Ions and Molecules

The stability of ions and molecules is influenced by their electron configurations. NH4+ (ammonium) is stable because it has a full octet around nitrogen, but it carries a positive charge due to the extra hydrogen. NH2- (amide) is less stable because it has an incomplete octet and carries a negative charge, making it more reactive. Stability is often associated with achieving a full outer electron shell, which is not the case for NH2-.