Chemistry- Naming Monatomic Ions

What is a monatomic ion?!

Watch the video here!

Let's get some background information.

Think back to electron configurations and bonding. Remember how all elements "strive" for balance - for that full outer orbital?

Many elements achieve this through chemical bonding, by either sharing electrons, stealing electrons, or giving up electrons to the partner in the bond.

There are some elements, however, that can give up electrons in their valance orbital to achieve the ideal full orbital! These elements can to this with one atom - thus they are called "monatomic ions." The prefix "mono" or "mon in this case" translates to 1 or single. Of course, atomic refers to a single atom. Thus, the term translates to single atom ions.

There are some results to this. But first, we need to take the time to really understand the parts of an electron, because a lot of naming and chemical reactions deals with charge. So, go here (an older blog of mine), read about charges. Do not worry so much about oxidation and reduction, we will get around to that, so you can stop reading when you read this part "Answer: the charge", and come back to this page.


So, to recap the important points, electrons are negative and protons are positive. Atoms with an unequal number of protons and electrons will have a charge; we call those ions. A positively charged ion is a cation, resulting from having fewer electrons than protons. Oppositely, an atom can gain electrons. Having a surplus of electrons compared to protons, then, results in an anion, which is a negatively charged ion. Take the equations below for example.

3 p - 3 e = 0 BUT 3 p - 2 e = 1 which is positive!
3 p - 3 e = 0 BUT 2 p + (-3 e) = -1 which is negative!


Read in your text book (Modern Chemistry by Holt, Rinehart and Winston, 1999) Chapter 7 pages 204 and 205 about  Monatomic ions. If you do not have your text, click here for a link to photo image of the pages.

Based on the number of electrons in the valence shell, atoms will either give up or gain electrons. You have learned some about electronegativity in bonding, where elements at the left of the table are less electronegative and those at the right side are highly electronegative. This is because there are less outer electrons in left elements, and more in right elements. Look at the table below:
This table shows the elements that are able to engage in forming monatomic ions - those which are considered "main group" elements.

Note that above each column, the charge of the atom as an ION is provided. This means that the atom has gained or lost electrons - it has a charge.

Take a look at the forming of cations. What is the charge of a cation? (POSITIVE! less electrons)

 To form cations, atoms from column 1 lose 1 electron, gaining a positive 1 charge. study the chart and write what happens for the other columns.

Now, let's look at anions. What is the charge of an anion? (NEGATIVE! more electrons)

Notice here that Hydrogen is included here. To obtain a full outer shell, Hydrogen will gain an electron. Hydrogen, though, is tricky. MOST of the time in chemical reactions, it will gain an electron, becoming an anion. However, the single electron that hydrogen carries is very often stripped away in biochemical reactions like photosynthesis so that the electron can be used as pure energy in the formation of sugar from the sun. As fascinating as that is, we will not go further into details about that, and for the sake of this course, consider H as forming anions.

NAMING!!! 

So finally, now that you know which way these atoms swing in ion formation, we must name them.

Cations are simple. You just give the name of the element and add the word "cation" at the end.
Examples:

K⁺ is "Potassium cation" and Mg²⁺is "Magnesium cation"

Anions are a little different. Part of the end of the element's name is removed and an -ide ending is added. The word anion is NOT used.
Examples:

F^- is "Fluoride" and N^3- is "Nitride"

Below is a picture of a table from the course text (Davis, R. E., & Holt, R. (1999). Modern chemistry: [Gr. 9-12]. Austin, Tex: Holt, Rinehart and Winston.) on page 205. This table shows the common monatomic ions.

You will notice that in the d-block list of atoms, there are some names which include roman numerals, related to the stock system of naming elements and chemical ions. Here is a quick link to the rules (which we will discuss with  section 7-2). In summary, the roman numerals are used when there are different possible charges for the cation. Meaning that sometimes, the atom might lose 2 elections (gaining a 2+ charge), while others it could lose 3 (gaining a plus 3 charge). In the first case, a numeral of II would represent the oxidation number of 2, while in the second case, there would be a numeral of III to represent that the ion for that particular element used in this case is the one which has lost 3 electrons.

When the table mentions "d-block," they are referring to the orbitals discussed in chapter 4. the d-block elements are transition metals, and are ofter very unique. Below is the periodic table with the orbitals provided to refresh your memory.