What is the molecular geometry of the ion?
Choose one:
A linear
B T-shaped
C seesaw
D trigonal planar
E square planar
F octahedral
G trigonal bypyramidal
H trigonal pyramidal
I square pyramidal
J tetrahedral
K bent
The correct answer and explanation is :
To determine the molecular geometry of an ion, we need to know its Lewis structure, valence shell electron pair repulsion (VSEPR) theory, and electron domain geometry. However, you haven’t specified which ion you are referring to, so I’ll explain the general approach and then consider an example.
Steps to Determine Molecular Geometry
- Draw the Lewis Structure – Identify the number of valence electrons and arrange them around the central atom.
- Count Electron Domains – Count bonding pairs and lone pairs around the central atom.
- Apply VSEPR Theory – Predict the molecular shape based on the number of electron pairs and lone pairs.
Example: Sulfate Ion (SO₄²⁻)
- Lewis Structure: Sulfur is the central atom, forming four single bonds with oxygen.
- Electron Domains: 4 (all bonding pairs, no lone pairs).
- VSEPR Shape: Since there are four bonding pairs and no lone pairs, the shape is tetrahedral.
- Correct Answer: J) Tetrahedral.
Example: Nitrite Ion (NO₂⁻)
- Lewis Structure: Nitrogen is the central atom with one lone pair and two bonded oxygen atoms (one with a double bond, one with a single bond and a negative charge).
- Electron Domains: 3 (two bonding pairs, one lone pair).
- VSEPR Shape: Bent (K).
General Rule for Common Molecular Geometries
- Linear (A) – Two bonding groups, no lone pairs (e.g., CO₂).
- Trigonal Planar (D) – Three bonding groups, no lone pairs (e.g., NO₃⁻).
- Tetrahedral (J) – Four bonding groups, no lone pairs (e.g., SO₄²⁻).
- Bent (K) – Two bonding groups, one or two lone pairs (e.g., NO₂⁻, H₂O).