1. Naturally occurring potassium ions are K+
QUESTION:
Which of the following naturally-occurring ions is paired with its correct symbol? A. potassium ion, K2+, B. sulfide, S3- C. barium ion, Ba D. iodide, I+ K+
S2-
Ba2+ I-
Naturally occurring potassium ions are K+
We use the periodic table to predict charges of naturally-occurring monatomic ions.
SCRIPT:
Which of the following naturally-occurring ions is paired with its correct symbol? Potassium ion, sulfide, barium, or hydride
PAUSE
Let’s examine choice A.
K is the symbol for a potassium atom, … and K2+ is the symbol for a potassium ion formed when the atom loses two electrons.
It can happen.. But only under certain conditions. In nature, you’re not going to find any potassium ion with a charge of +2.
All the potassium ions you’ll find have a charge of So choice A is wrong.
When you do see a question like this on a test, chances are you will not see the phrase “naturally-occurring”. Unless you are given
information to the contrary, you should just assume that the question is referring naturally-occurring ions.
CLICK
We can use the periodic table to predict charges of naturally-occurring monatomic ions.
By monatomic ion, we mean an ion obtained from an atom losing or gaining electrons.
Naturally occurring monatomic ions from group 1A all have a charge of +1.
CLICK Potassium is in this group, so potassium ions have a charge of +1.
CLICK HIGHLIGHT K in periodic table.
Naturally occurring monatomic ions from group 2A all have a charge of +2
Barium is in this group, barium ions have a charge of +2.
CLICK HIGHLIGHT Ba in periodic table.
The halides, … the ions formed from the halogens, which are found in column 17 or group 7A,
All have a –1 charge. Iodine is a halogen…
CLICK Therefore, iodide, choice D, has a -1 charge.
HIGHLIGHT I in periodic table
The naturally occurring monatomic ions from the nonmetals of group six A all have a charge of –2.
CLICK Sulfur is in this group.
CLICK Therefore, sulfide, has a charge of –2.
HIGHLIGHT Sulfur in periodic table.
Therefore the correct answer is C.
Among the choices, only barium ion is written with its correct formula.
CONTINUED ON NEXT SLIDE +1 +2 -2 -1

2. Variable (+1 to +4) Most common: +2
Hydrogen: H+
Hydride: H- -3 +3 -2 -1
Variable (+1 to +4) Most common: +2 +1 +2
Group IA: +1
Group IIA): +2
Al: +3
Transition and post-transition: variable; Zn, Cd, Hg: +2
Here’s a summary of naturally occurring monatomic ions…
Monatomic ions derived from metallic elements all have a positive charge.
CLICK Monatomic ions derived from group 1A are always found to have a +1 charge.
CLICK
For group 2A, the charge is always +2.
Aluminum ion is always found to have a +3 charge.
CLICK Transition and post-transition metals tend to form ions with different charges.
The most common charge is +2.
To repeat, +1 for the alkali metals.
+2 for the alkaline earth metals
CLICK +3 for aluminum
CLICK CLICK CLICK CLICK More than one possible charge, usually ranging from +1 to +4
For the transition and post-transition elements
The most commonly found charge is +2.
Note that monatomic ions from Zinc, Cadmium, and mercury are always found to have a charge of +2
HIGHLIGHT Zn, Cd, and Hg.
CLICK Nonmetals, on the other hand, tend to form ions with a negative charge.
CLICK The halogens, group 7A, always form ions with a –1 charge. All halides have a –1 charge.
CLICK For Group 6A, the charge is always –2
CLICK For Group 5A, the charge is always –3.
TO repeat, the charges are..
CLICK -1 for the halides
-2 for ions from nonmetal atoms of group 6A
CLICK -3 for ions from nonmetal atoms of group 5A
CLICK Hydrogen tends to form two possible ions.
The ion with +1 charge is called hydrogen ion.
CLICK The ion with –1 charge is called hydride ion.
What about the other elements we left out.
The inner transition elements should be similar to the transition elements.
All the others, including carbon, the metalloids and noble gases tend not to form monatomic ions.
Carbon and the metalloids tend to form covalent bonds,… that is, they tend to share electrons.
Noble gases, on the other hand, are inert. They tend not to lose, gain, or share electrons.
CLICK PAUSE END RECORDING
Nonmetals: Group VIIA: -1
Group VIA: -2
Group VA: -3

3. 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