Monatomic Ions: Definition & Naming Convention

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  • 0:00 What Is A Monatomic Ion?
  • 1:50 Positive vs. Negative Ions
  • 3:30 Naming Monatomic Ions
  • 4:33 Lesson Summary
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Lesson Transcript
Instructor: Elizabeth (Nikki) Wyman

Nikki has a master's degree in teaching chemistry and has taught high school chemistry, biology and astronomy.

In this lesson, discover what it means to be a monatomic ion and learn some helpful examples. Then you will learn the naming convention for monatomic ions.

What is a Monatomic Ion?

Individuals that have played with magnets might know that two oppositely charged magnets will stick to each other, while two magnets of the same charge will repel each other. Well, think of a single, charged magnet as a monatomic ion. Monatomic ions can be positive or negative and just like magnets, oppositely charged ions will attract, and ions with the same charge will repel each other.

It is helpful to think of monatomic ions as simple magnets
Simple refrigerator magnets

A good way to remember this definition is to break the term monatomic ion into its component parts. The prefix mon- or mono- means one. The suffix -atomic refers to an atom. Thus monatomic means one atom. The term ion means charged particle. Combined, we have our definition for monatomic ion. A monatomic ion is a charged particle that consists of only one atom.

The charge on the ion may be positive or negative. Additionally, the size of the charge may vary; for example, some ions have a 1- charge (like on a chlorine atom) while others, like a nitrogen atom, are capable of carrying a 3- charge. Similarly, some ions can carry a 1+ charge (like sodium), and others can have up to a 4+ charge (like vanadium)! Many atoms are capable of having multiple charges. Copper, for example, can have a 1+, 2+ or 3+ charge.

cartoon of different ions

Monatomic ions are chemically represented by the element's symbol with the size and type of charge written as a superscript to the right of the symbol. If the size of the charge is one, then the type of charge (+ or -) is all that is written.

For example, the magnesium 2+ ion is written as Mg2+.

The fluorine 1- ion is written as F-.

Positive vs. Negative Ions

Positively charged ions are called cations. Negatively charged ions are called anions.

Can all elements form both cations and anions? The answer is no! With the exception of hydrogen, single elements generally only form one type of ion. Metal elements always form cations, non-metals always form anions. The periodic table provides reference for distinguishing metals from nonmetals.

Metals and non-metals distribution on the periodic table.

Metals are elements that are generally shiny, silvery, good conductors of heat and electricity and solid at room temperature. They are located on the left side and middle region of the periodic table. They are separated from non-metals by the thick dark staircase on the right side of the periodic table. Non-metals are elements that are poor conductors, they are variously colored and generally exist as a gas at room temperature.

Many of the transition metals, located in the middle of the periodic table are capable of forming differently charged cations. Hydrogen, up in the top left corner is special in that it can be either a 1+ cation or a 1- anion!

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