*Its All about Pj Problem Strings (S _{i}P_{j}A_{jk}) -
7 Spaces Of Interest (S_{i}) and their associated Basic Sequences; 7 Pj Problems of Interest (PPI) and their Alleles (A_{jk})*

Expressions Of Pj Problems.

Pj Problems - Overview

Celestial Stars As Expressions Of Pj Problems

The Number Line As Expression Of Pj Problems

Geometries As Expressions Of Pj Problems

7 Spaces Of Interest - Overview

Triadic Unit Mesh

Creation As Expression Of Pj Problems

The Atom As Expression Of Pj Problems

Survival As Expression Of Pj Problems

Energy As Expression Of Pj Problems

Light As Expression Of Pj Problems

Heat As Expression Of Pj Problems

Sound As Expression Of Pj Problems

Music As Expression Of Pj Problems

Language As Expression of Pj Problems

Stories As Expressions of Pj Problems

Work As Expression Of Pj Problems

States Of Matter As Expressions Of Pj Problems

Buoyancy As Expression Of Pj Problems

Nuclear Reactions As Expressions Of Pj Problems

Molecular Shapes As Expressions Of Pj Problems

Electron Configurations As Expressions Of Pj Problems

Chemical Bonds As Expressions Of Pj Problems

Energy Conversion As Expression Of Pj Problems

Chemical Reactions As Expressions Of Pj Problems

Electromagnetism As Expression Of Pj Problems

Continuity As Expression Of Pj Problems

Growth As Expression Of Pj Problems

Human-cells As Expressions Of Pj Problems

Proteins As Expressions Of Pj Problems

Nucleic Acids As Expressions Of Pj Problems

COHN - Nature's Engineering Of The Human Body

The Human-Body Systems As Expressions Of Pj Problems

Vision As Expression Of Pj Problems

Walking As Expression Of Pj Problems

Behaviors As Expressions Of Pj Problems

Sensors' Sensings As Expressions Of Pj Problems

Beauty As Expression Of Pj Problems

Faith, Love, Charity As Expressions Of Pj Problems

Photosynthesis As Expressions Of Pj Problems

Weather As Expression Of Pj Problems

Systems As Expressions Of Pj Problems

Algorithms As Expressions Of Pj Problems

Tools As Expressions Of Pj Problems

Networks As Expressions Of Pj Problems

Search As Expressions Of Pj Problems

Differential Calculus As Expression Of Pj Problems

Antiderivative As Expression Of Pj Problems

Integral Calculus As Expression Of Pj Problems

Economies As Expresions Of Pj Problems

Inflation As Expression Of Pj Problems

Markets As Expressions Of Pj Problems

Money Supply As Expression Of Pj Problems

Painting As Expressions Of Pj Problems

Predicting Molecular Shape With The VSEPR Model

Precise molecular shapes are determined by the bond lengths and bond angles established by the bonding atoms. However, the *Valence Shell Electron Pair Repulsion* (VSEPR) model predicts molecular shapes fairly well. Here, we examine VSEPR as it relates to the prediction of molecular shapes of AB molecules.

1. Define the following: (a) AB_{n} molecules (b) Lewis Electron-Dot Diagram (c) Electron Domain.

2. Determine the Lewis structure for the following molecules:
(a) CO_{2} (b) H_{2}O (c) BF_{3} (d) XeF_{4}
(e) CCl_{4} (f) NH_{3} (g) PCl_{5} (h) SF_{6}

3. Use the *Valence-Shell Electron-Pair Reduction* (VSEPR) model to predict the molecular shapes and bond angles of the molecules indicated in problems 2a, 2c, 2e, 2g and 2h.

4. Predict the molecular geometries of the molecules of 2b, 2d and 2f, from the electron-domain geometries of problem 2. Will the bond angles of these molecules be greater or smaller than the bond angles indicated in the electron-domain geometries from which their molecular geometries were derived?

5. Write a general representative string for the VSEPR model.

1(a) AB_{n} molecules are molecules with a central atom (A) and n similar atoms (B) bonded to A. For example CO_{2} (where carbon is the A atom and oxygen the B atoms with n =2).

1(b) The Lewis Dot Diagram is the representation of an atom, ion, or molecule such that the element's symbol represents the nucleus and all inner shell electrons while the dots that surround the symbol represent the valence electrons. The diagram is also called the *Lewis structure* of the atom, ion or molecule.

1(c) *Electron domain* refers to the region occupied by *non-bonding pair of electrons*, a *single covalent bond*, or *multiple covalent bonds* around the central atom of an *AB _{n}* molecule.

2. The Lewis structures for the molecules are:

3. The general steps for using the VSEPR model is as follows:

(i). Determine the Lewis structure of the molecule or ion, then count the total electron-domains around the central atom. Each *nonbonding pair*, *single bond*, or *multiple bond* around the central atom counts as an *electron-domain*.

(ii). Determine the *electron-domain geometry* by arranging the electron-domains about the central atom in a manner that minimizes the electron repulsion among them.

(iii). Use the arrangement of the bonded atoms to determine the *molecular geometry*
of the molecules.
* CO _{2}*:

Electron domains = 2; bonding domains = 2; nonbonding domains = 0; electron geometry = linear; molecular geometry = linear; bonding angle = 180

Electron domains = 3; bonding domains = 3; nonbonding domains = 0; electron geometry = trigonal planar; molecular geometry = trigonal planar; bonding angle =120

Electron domains = 4; bonding domains = 4; nonbonding domains = 0; electron geometry = tetrahedral; molecular geometry = tetrahedral; bonding angle = 109.5

Electron domains = 5; bonding domains = 5; nonbonding domains = 0; electron geometry = trigonal bipyramidal; molecular geometry = trigonal bipyramidal; bonding angle between axial and equatorial bond = 90

.

Electron domains = 6; bonding domains = 6; nonbonding domains = 0; electron geometry = octahedral; molecular geometry = octahedral; bonding angle between axial and equatorial bond = 90

4. *H _{2}0*:

electron domains = 4; bonding domains = 2; nonbonding domains = 2; electron geometry = tetrahedral; molecular geometry = bent (tetrahedral minus 2 electron domains); bond angle will be less than 120

electron domains = 6; bonding domains = 4; nonbonding domains = 2; electron geometry = octahedral; molecular geometry = square planar (ocahedral minus 2 axial electron domains); bond angle 90

electron domains = 4; bonding domains = 3; nonbonding domains = 1; electron geometry = tetrahedral; molecular geometry = trigonal pyramidal (tetraahedral minus 1 electron domain); bond angle will be less than 120

5. The VSEPR model is based on repulsion so the general representative string is:

(S_{7}P_{3}A_{32})_{repulsion}

Mind Warm Ups

The *point* "**.**" is a mathematical abstraction. It has negligible size and a great sense of position. Consequently, it is front and center in abstract existential reasoning.

*Problems by Peter O. Sagay*