1. Each calcium ion has a charge of +2,
QUESTION:
What is the formula of an ionic compound consisting of Ca2+ and Cl- ions? A. CaCl, B. Ca2Cl, C. CaCl2, D. Ca2Cl2
The formula of an ionic compound reflects the simplest combination of cations and anions with a total charge of zero
Cations: +2, +2, +2, +2, +2, +2, …
Anions , -1, -1, -1, -1, -1, …
SCRIPT:
What is the formula of an ionic compound consisting of calcium and chloride ions? A. CaCl, B. Ca2Cl, C. CaCl2, D. Ca2Cl2
PAUSE
CLICK
The formula of an ionic compound reflects the simplest combination of cations and anions with a total charge of zero.
Each calcium ion has a charge of +2,
HIGHLIGHT calcium ion in the question
…and each chloride ion has a charge of –1.
HIGHLIGHT
So, let’s imagine we have a collection of calcium ions Remember that each one has a charge of +2.
CLICK and a collection of chloride ions. Each of these ions has a charge of –1.
The simplest combination of ions with a total charge of zero consists of
One calcium ion,
CLICK and two chloride ions…
This combination,… two cations and one anion,… gives us a total charge of zero….. +2 ….plus –1 times 2…. equals zero.
The corrrect answer is choice C.
One formula unit of this compound consists of one cation and two anions. The formula is CaCl2.

2. Video ID: © 2008, Project VALUE (Video Assessment Library for Undergraduate Education), Department of Physical Sciences Nicholls State University Author: Glenn V. Lo Narrator: Funded by Louisiana Board of Regents Contract No. LA-DL-SELECT-13-07/08