1. Na2S is a binary, ionic compound. Binary: two elements (Na and S)
QUESTION:
Which of the following is the correct name for Na2S? A. sodium sulfide, B. disodium sulfide C. sodium sulfite, D. sodium sulfate
Na2S is a binary, ionic compound.
Binary: two elements (Na and S)
Ionic: metal + nonmetal
Rule: name the cation, then the anion
Name of cation = name of metallic element
Name of anion = name of nonmetallic element, but change ending to ide
Do not use Greek prefix.
SCRIPT:
Which of the following is the correct name for Na2S? A. sodium sulfide, B. disodium sulfide C. sodium sulfite, D. sodium sulfate
PAUSE
To name a compound given its formula, we need to first classify the compound, then apply the rule for that type of compound.
CLICK
Na2S is a binary, ionic compound.
By binary, we mean that it is made up of only two elements…. In this case, sodium and sulfur
CLICK It’s an ionic compound because one of the elements, sodium, is a metallic element, and the other, sulfur, is nonmetallic. If both were nonmetals, the compound would be molecular.
The rule for naming binary ionic compound is this.
Name the cation, then the anion
The cation is the positive ion, …the ion derived from the metallic element… Its name is simply the name of the metallic element. This is the case for all four choices given here. The name of the cation is sodium.
CLICK The anion is the negative ion, … the ion derived from the nonmetallic element…. Its name is the name of the nonmetallic element, but with the ending changed to ide.
HIGHLIGHT ide
Therefore, we can rule out choices C and D. These don’t end in ide.
CROSS OUT “ite” and “ate” in choices C and D
We can also rule out choice B. The name of the anion is simply chloride, not dichloride.
CROSS OUT “di” in choice B
We do not use Greek prefixes when naming ionic compounds.
CLICK PAUSE END RECORDING

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