Modeling Geometry and Polarity

How many total valence electrons are present in a molecule of PCl3? ?

26

How many total electron pairs are in the structure of CS2?

8

Identify each term as a description of an electron geometry or a molecular geometry.

Arrangement of only the atoms in a molecule → Molecular geometry Arrangement of bonding and non-bonding electron domains → Electron geometry Tetrahedral for NF3→ Electron geometry Trigonal pyramidal for NF3 →Molecular geometry

Table B.1 Geometry and Polarity of Group T Compounds

CH4, tetrahedral, 4, tetrahedral, 4, Yes, No NH3, tetrahedral, 3, trigonal pyramidal, 3, No, Yes H2O, tetrahedral, 2, 2, bent, 2, No, Yes BH3, 3, trigonal planar, 3, 0, trigonal planar, 3, Yes, No SO2, 3, trigonal planar, 2, 1, bent, 2, No, Yes CO2, 2, linear, 2, 0, linear, 2, Yes, No

Suppose you mix an unknown solid with oil and the added solid dissolves into the oil. What is most likely true about the unknown solid?

It is a non-polar solid.

Determine whether each of the molecules below is polar or nonpolar

Linear F2→ Nonpolar Tetrahedral SiF4→ Nonpolar Linear CO→Polar Trigonal planar BCl3→Nonpolar

Table B.2 Geometry and Polarity of Group W Compounds

N2, N/A, N/A, N/A, N/A, N/A 0, N/A,No HCN 2, linear, 2, 0, linear, 2, No, Yes H3O+, 4, tetrahedral, 3, 1, trigonal pyramidal, 3, No, Yes

Examine the images for sodium chloride (an ionic salt), and three covalently bonded substances: table sugar (sucrose),iodine crystals and sulfur. Record two or three physical properties you observed (macroscopic) about each substance.

Sodium chloride NaCl. Ionic Cube shaped with soft edges. NaCl is transluscent and resembles ice. Color is white/clear. Sucrose C12H22O11 Polar covalent Sucrose is irregular shaped, but still looks 3D. Sucrose is transparent and is clear in color. Iodine I2 Non-polar covalent Iodine has a charcoal-metallic color and some luster. The shape is irregular, and has a rugged surface. Sulfur S8 Non-polar covalent Sulfur has the pale-yellow color of a semi-ripe banana peel. It looks fragile and crumbly.

For each atom, determine how many dots should be drawn around the element symbol in the Lewis structure for a lone, neutral atom

The Lewis structure of an oxygen atom should have 6 dots drawn around the symbol O. The Lewis structure of a calcium atom should have 2 dots drawn around the symbol Ca. The Lewis structure of a nitrogen atom should have 5 dots drawn around the symbol N. The Lewis structure of an aluminum atom should have 3 dots drawn around the symbol Al. The Lewis structure of a fluorine atom should have 7 dots drawn around the symbol F.

What characteristics of a molecule determine whether or not it is polar?

The polarity of the individual bonds in the molecule The arrangement of bonds around the molecule

Describe the atomic (microscopic) perspective of a sodium chloride crystal as shown in the computer modeling software.

The sodium chloride crystal is uniformly packed tightly together. This indicates that it is a solid. Each ion is surrounded by opposite charged ions