Physical Science Chapter 23

Single Bond

A covalent bond involving one pair of electrons shared between the two bound atoms. In chemical structure drawings, single bonds are represented by single lines.

Intermolecular

Between molecules (as opposed to intramolecular, within molecules)

Polar

Bonds or molecules having an unequal distribution of charge (one end being positive, the other negative)

Valence Shell

The outermost, highest-energy set of orbitals in an atom. The arrangement of electrons in the valence shell determines how the atom interacts chemically with other atoms.

Dipole

The separation of positive and negative charge in a polar bond or molecule

B

When some Ca(NO3)2 dissolves in water which picture best represents what the solution looks like? (Note, the balls are not meant to indicate charge or lack of charge.)

Electronegativity

A measure of how strongly atoms attract electrons. Both ionization energy (the energy required to remove an electron from a neutral atom) and electron affinity (the energy gained when an electron is added to a neutral atom) contribute to electronegativity. Electronegativity increases from left to right across rows and decreases down columns of the periodic table

When do polyatomic ions form crystals? a. When they combine with metal atoms to form salts. b. When they combine with other non-metal atoms. c. never. d. A and B.

a. When they combine with metal atoms to form salts. b. When they combine with other non-metal atoms.

How would you describe the melting point of a substance formed by a substance containing molecular ions? a. extremely low b. low c. high

c. high

Basic

having a pH value greater than 7, meaning that the hydronium ion concentration is less than in pure water

Triple Bond

A covalent bond involving three pairs of electrons shared between the two bound atoms. In chemical structure drawings, triple bonds are represented by triple lines

Double Bond

A covalent bond involving two pairs of electrons shared between the two bound atoms. In chemical structure drawings, double bonds are represented by double lines

pH

A logarithmic measure of the concentration of hydronium ions in water. pH values less than 7 describe acidic solutions. pH = 7 is neutral and pH values greater than 7 indicate the solution is basic

Solvent

A material (typically a liquid) in which another material dissolves.

Hydrocarbons

Chemical compounds between the elements carbon and hydrogen. The compounds that make up gasoline are examples

Molecular Ions

Groups of atoms covalently bound to each other that have a net charge because electrons have been lost or gained to facilitate formation of the covalent bonds. Also known as polyatomic ions.

Acidic

Having a pH value less than 7, meaning that the hydronium ion concentration is greater than in pure water

Hydrogen Bonding

Interactions between hydrogen atoms bound to oxygen, nitrogen, or fluorine with other oxygen, nitrogen or fluorine atoms. Hydrogen bonds are among the strongest inter-molecular interactions

Organic Molecules

Molecules that have a central framework of carbon atoms. Originally, it was thought that organic molecules could only be produced in living organisms, hence the name. Now it is clear that the molecules can be produced abiologically.

Self-ionizatoin

The reaction of certain neutral molecules (such as water) with other identical molecules to produce cations and anions.

Dispersion Forces

Weak intermolecular attraction arising from the formation of temporary dipoles in non-polar molecules. Also known as van der Waals forces

In carbon tetra-chloride, CCl44, what is true about the charge distribution? a. The carbon will be more negative than the chlorine. b. The chlorine will be more negative than the carbon. c. The chlorine and carbon would be equally negative. d. The atoms will become positive and negative ions. e. It is impossible to predict how the electrons will distribute themselves in this type of bond.

b. The chlorine will be more negative than the carbon.

Which of the following would best describe the characteristics of covalent materials? a. A brittle, transparent solid with a very high melting point. b. A shiny, malleable solid with a very high melting point. c. A non-conducting material with low melting and boiling points, likely liquid or gas at room temperature. d. A brittle, opaque solid with a very high melting point. e. A non-conducting solid at room temperature that will conduct if melted or dissolved.

c. A non-conducting material with low melting and boiling points, likely liquid or gas at room temperature.

When are molecules conductors of electricity? a. When they combine with metal atoms to form salts. b. When they combine with other non-metal atoms. c. When they combine with metals and are then melted or dissolved d. Never.

c. When they combine with metals and are then melted or dissolved

Which of the following is a true statement about melting and boiling points in materials made of covalent molecules? a. Molecules that contain double bonds melt and boil at higher temperatures because the bonds are stronger. b. Molecules that contain triple bonds are the most likely to be gases at room temperature. c. Molecules that are polar have lower melting and boiling points than non-polar molecules. d. Hydrogen bonding between molecules increases melting and boiling points. e. Van der Waals (dispersion) forces lower melting and boiling points.

d. Hydrogen bonding between molecules increases melting and boiling points.

What best describes how oxygen molecules would behave if mixed with water? Select one: a. They would dissolve well because they are polar. b. They would dissolve well because they are not polar. c. They would dissolve poorly or not at all because they are polar. d. They would dissolve poorly or not at all because they are not polar. e. They would dissolve well because they are ionic.

d. They would dissolve poorly or not at all because they are not polar.

Covalent

materials characterized by chemical bonds that involve sharing electrons. Typically, the bonds in covalent substances occur between non-metal atoms