Naming Monoatomic Cations: Study with Video Lessons, Practice Problems & Examples

Cations retain their elemental name with "ion" added. For metals with multiple charges, Roman numerals indicate the charge, e.g., vanadium 3+ is "vanadium III ion." In older naming, the lesser charge uses the suffix "-ous" and the greater charge uses "-ic," such as "chromous ion" for Cr²⁺ and "chromic ion" for Cr³⁺. This naming convention also applies to copper (cuprous/cupric) and iron (ferrous/ferric), reflecting their Latin roots. Understanding these naming systems is crucial for accurately identifying and communicating about ionic compounds.

Naming Monoatomic Cations Concept 1

Here we deal with the naming method where a cation always keeps its name and has the word ion added to its end. Now we're going to say here, if the metal possesses multiple charges, we must use a Roman numeral before adding ion to its name. So, for example, let's say we're looking at vanadium here. Vanadium has 4 possible charges here, plus 2, plus 3, plus 4, or plus 5. So we need to utilize Roman numerals to describe which one in particular we're looking at. So let's say we're looking at vanadium with a charge of 3 plus. Its name would be vanadium, and the Roman numeral III, ion. Now if the metal possesses one charge, so just a single charge, then we don't have to worry about a Roman numeral. So for example, we're going to say the metals in group 1A are all plus 1, the metals in group 2A are all plus 2, the metals in group 3A are plus 3. So we wouldn't require a Roman numeral for them. So for example, magnesium, we wouldn't have to say magnesium II ion, we would just say magnesium ion. So keep this in mind when discussing the name of a cation.

Naming Monoatomic Cations Example 1

Provide the systematic name for the following ion. So we have Fe³⁺. If you look at Fe on your periodic table, you'll see that it's called iron. Iron is one of the elements that possesses multiple charges, and because of that, it requires a Roman numeral. Here it's 3 plus, so the name of this ion would be iron(III) ion. So here that would be the answer, is option D. Options A, B, and C just wouldn't work.

Naming Monoatomic Cations Concept 2

So the common name of cations requires an older naming method, and we'll use this older naming method for cations that possess multiple charges. Here, we won't be using Roman numerals; instead, we'll employ an older system for naming these particular types of cations. Now realize under this system, the lesser charge of the cation uses the suffix or ending of -ous, whereas the greater charge uses the suffix of -ic. So how exactly do we approach this? Here we have metal cation suffixes. We have the element name, ion symbol, systematic name, and then we have our common name. Alright. So we're going to say here that chromium exists as either Cr2+ or Cr3+. The systematic name is what we've learned earlier. Because they possess multiple charges, we can use Roman numerals under the systematic name. This one will be chromium(II) because it's 2+ and this would be chromium(III) ion. Now under the common naming system, we're going to say that this 2+ is the lesser charge. And because it's the lesser charge, it uses the ending -ous. So this would be chromous ion. 3+ is the higher or greater charge of this particular ion, so it uses the ending -ic, so this would be chromic ion. Copper can be 1+ or 2+, so we're going to say here this is copper(I) and this is copper(II) ion. Here would be cuprous ion, and this would be cupric ion. Iron can be 2+ or 3+, so this would be iron(II), and this would be iron(III). Now, you might be noticing that, hey, it's iron here, but it's ferrous here and ferric there. That's because the common names are also tied to the Latin names for some of these elements. Realize that copper here uses the symbol Cu, iron uses Fe. That's because these element symbols are based on their Latin root names, and the common name highlights this fact. Alright. So iron 2+ is the lesser charge, so this is ferrous ion. 3+ is the higher charge, so this is ferric ion. Alright. Mercury is a little bit weird. Mercury can exist as a pair and together they are 2+. That means each one is actually 1+. So this would be mercury(I) ion, and this would be mercury(II) ion. This would translate to mercurous ion and mercuric ion. Finally, we have tin which is Sn. Again, Sn here doesn't match the name Tin; that's because Sn is based on the Latin name for it. So tin can be 2+ or 4+, so this would be tin(II) and tin(IV), which would translate to stannous ion and stannic ion. So just remember, we use this common naming method for cations with multiple charges. The lower charge uses the ending of -ous. The higher charge uses the ending of -ic.

Naming Monoatomic Cations Example 2

If a fictional ion has a prefix of unper, name its lesser charged ion using the common naming system. Right. So if we're using a lesser ion, remember, that means the suffix or ending would be ose. So that means that will be called on. So that would mean that option b would be our correct answer. Remember, the lesser charge uses the ending "ose", the higher charge uses the ending "ic". So if we wanted the name of the higher charged ion form, it would be onpyric ion in that case.

Here’s what students ask on this topic:

What is the naming convention for monoatomic cations with multiple charges?

For monoatomic cations with multiple charges, the naming convention involves using Roman numerals to indicate the specific charge of the cation. For example, vanadium can have charges of +2, +3, +4, or +5. If we are referring to vanadium with a charge of +3, it is named 'vanadium III ion.' This system helps to clearly specify which ion is being discussed, especially for transition metals that can have multiple oxidation states.

How do you name a monoatomic cation with a single charge?

For monoatomic cations with a single charge, the naming is straightforward. The cation retains its elemental name followed by the word 'ion.' For example, magnesium, which always has a charge of +2, is simply named 'magnesium ion.' There is no need to use Roman numerals for these cations because their charge is always the same.

What is the older naming method for cations with multiple charges?

The older naming method for cations with multiple charges uses suffixes instead of Roman numerals. The lesser charge of the cation uses the suffix '-ous,' while the greater charge uses the suffix '-ic.' For example, Cr²⁺ is called 'chromous ion,' and Cr³⁺ is called 'chromic ion.' This method also often reflects the Latin roots of the element names, such as 'ferrous ion' for Fe²⁺ and 'ferric ion' for Fe³⁺.

Why do some cations have Latin-based names in the older naming system?

Some cations have Latin-based names in the older naming system because the symbols for these elements are derived from their Latin names. For example, the symbol for iron is Fe, which comes from its Latin name 'ferrum.' Therefore, Fe²⁺ is called 'ferrous ion,' and Fe³⁺ is called 'ferric ion.' Similarly, copper (Cu) is derived from 'cuprum,' leading to 'cuprous ion' for Cu⁺ and 'cupric ion' for Cu²⁺.

How do you name the cation of mercury in the older naming system?

Mercury cations can be a bit unusual. Mercury can exist as Hg₂²⁺, where each mercury atom has a +1 charge, or as Hg²⁺ with a +2 charge. In the older naming system, Hg₂²⁺ is called 'mercurous ion,' and Hg²⁺ is called 'mercuric ion.' This distinction is important for accurately identifying the specific form of mercury in a compound.