Molecular Geometry Flashcards

Questions and Answers

What is VSEPR theory?

Valence shell electron pair repulsion theory is a model for predicting the molecular geometry of molecules based on the number of electron pairs around a central atom.

What is the bond angle in carbon dioxide and why?

180°

Use VSEPR theory to predict the molecular geometry around either carbon atom in acetylene, C2H2.

Linear

Use VSEPR theory to predict the molecular geometry of BrF5.

Square pyramidal Signup and view all the answers

Which of the following terms describe common molecular shapes? (Select all that apply)

Trigonal Pyramidal Signup and view all the answers

Which has the longest bond length?

All bond types are equal length Signup and view all the answers

What are the approximate I-N-I bond angles in NI3?

109.5° Signup and view all the answers

The shape of a molecule of NH3 is said to be?

Pyramidal Signup and view all the answers

What is bond order?

The number of electron pairs being shared by a given pair of atoms. A single bond consists of one bonding pair and has a bond order of 1. Signup and view all the answers

What is bond energy?

The energy needed to overcome the attraction between the nuclei and the shared electrons. The stronger the bond, the higher the bond energy. Signup and view all the answers

What is bond length?

The distance between the nuclei of the bonded atoms. Signup and view all the answers

Using the periodic table, rank the bonds in each set in order of decreasing bond length and decreasing bond strength: S-F, S-Br, S-Cl.

Bond length: S-Br > S-Cl > S-F; Bond strength: S-F > S-Cl > S-Br Signup and view all the answers

Using the periodic table, rank the bonds in each set in order of decreasing bond length and decreasing bond strength: C=O, C-O, C≡O.

Bond length: C-O > C=O > C≡O; Bond strength: C≡O > C=O > C-O Signup and view all the answers

What does V.S.E.P.R stand for?

Valence-Shell Electron-Pair Repulsion Theory Signup and view all the answers

What is molecular shape?

The three-dimensional arrangement of nuclei joined by the bonding groups. Signup and view all the answers

How is molecular shape classified?

Using the designation MXaEb Signup and view all the answers

What is a bond angle?

The angle formed by the nuclei of two surrounding atoms with the nucleus of the central atom. Signup and view all the answers

Study Notes

VSEPR Theory

Valence Shell Electron Pair Repulsion (VSEPR) theory predicts molecular geometry based on electron pair repulsion.
The shape of a molecule is determined by the number of electron pairs around a central atom.

Carbon Dioxide Bond Angle

Carbon dioxide has a bond angle of 180° due to its linear arrangement (MX2) with two double bonds to oxygen.

Acetylene Molecular Geometry

Acetylene (C2H2) has a linear geometry around each carbon atom because of the presence of a double bond.

BrF5 Geometry

The molecular geometry of bromine pentafluoride (BrF5) is square pyramidal.

Common Molecular Shapes

Six common molecular shapes include:
- Linear
- Trigonal Pyramidal
- Bent
- Trigonal Planar
- Tetrahedral
- Trigonal Bipyramidal

Bond Lengths and Types

A single bond has the longest bond length compared to double and triple bonds.
Bond length increases from triple to double to single bonds.

Nitrogen Triiodide (NI3) Bond Angles

The I-N-I bond angles in nitrogen triiodide (NI3) are approximately 109.5°.

Unexpected Bond Angles

A bond angle of 60° is not expected in any molecular structure.

Ammonia Shape

The shape of ammonia (NH3) is described as pyramidal due to its nonbonding electron pair on nitrogen.

Polar Molecule Identification

Water (H2O) is a polar molecule among the options given (CCl4, H2O, CO2, N2).

Most Polar Bond

Hydrofluoric acid (HF) contains the most polar bond compared to HBr, HCl, and H2O.

Nonlinear Structures

H2S is not a linear structure, unlike H-C≡C-H, I2, and CO2.

Central Atom Nonbonding Pairs

Ammonia (NH3) has a nonbonding pair of electrons on the central nitrogen atom.

Bond Order

Bond order signifies the number of shared electron pairs between two atoms; a single bond has a bond order of 1.

Bond Energy

Bond energy is the energy required to break a bond, correlating with bond strength; stronger bonds exhibit higher bond energy.

Bond Length

Bond length is defined as the distance between the nuclei of bonded atoms.

Periodic Table Bond Ranking (S Bonds)

For S-F, S-Br, S-Cl:
- Bond length: S-Br > S-Cl > S-F
- Bond strength: S-F > S-Cl > S-Br

Periodic Table Bond Ranking (C Bonds)

For C=O, C-O, C≡O:
- Bond length: C-O > C=O > C≡O
- Bond strength: C≡O > C=O > C-O

VSEPR Abbreviation

V.S.E.P.R stands for Valence-Shell Electron-Pair Repulsion Theory.

Molecular Shape

Molecular shape refers to the three-dimensional arrangement of nuclei linked by bonding groups, focused on relative positions.

Molecular Shape Classification

Classified using the notation MXaEb where:
- M = central atom
- X = surrounding atom
- E = nonbonding valence-electron group
- a and b are integers representing their quantities.

Bond Angle Definition

Bond angle is the angle formed by the nuclei of two surrounding atoms relative to the nucleus of the central atom.

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Description

Test your knowledge on molecular geometry concepts with these flashcards. Learn about VSEPR theory and bond angles in molecules such as carbon dioxide. Perfect for students studying chemistry.