The key difference between polyvalent element and polyatomic ion is that polyvalent elements have more than one valency whereas polyatomic ions have more than one atom that are covalently bonded to each other.
The prefix “poly-“ refers to “many”. In other words, if we name something using this prefix, it means there are more than one of that thing. For example, polyvalent means more than one valence and polyatomic means more than one atom.
CONTENTS
1. Overview and Key Difference
2. What is a Polyvalent Element
3. What is a Polyatomic Ion
4. Side by Side Comparison – Polyvalent Element vs Polyatomic Ion in Tabular Form
5. Summary
What is a Polyvalent Element?
Polyvalent element is a chemical element having more than one valency. In other words, these chemical elements involve in the formation of chemical bonds using different numbers of electrons. A synonym for this term is “multivalent element”. Some examples are as below:
- Iron shows two oxidation states as iron (II) and iron (III). This means iron can show two valences.
- Copper show two oxidation states as copper (I) and copper (II). Copper can remove either one electron or two electrons when forming a chemical bond.
- Chromium show chromium (II), (III) and (VI) oxidation states commonly.
What is a Polyatomic Ion?
Polyatomic ion is a chemical species which has a charge and more than one atom. This can be either positively charged (cation) or negatively charged (anion). In contrast, single atoms having a charge are monoatomic ions.
Figure 01: A Diagram showing Polyatomic Ion
When naming such compounds, there are two rules we need to obey. Firstly, we have to use the prefix “bi-“ if there is hydrogen in the chemical formula and naming the ion depending on the number of oxygen atoms present in the ion. For example, carbonate anion is a polyatomic ion (CO32-) and when we add a hydrogen atom to it, then we call the ion bicarbonate (HCO3–). The second rule of nomenclature considers the number of oxygen atoms present in the ion, i.e. ClO2– is chlorite and ClO3– is chlorate.
What is the Difference Between Polyvalent Element and Polyatomic Ion?
The key difference between polyvalent element and polyatomic ion is that polyvalent elements have more than one valency whereas polyatomic ions have more than one atom that are covalently bonded to each other. When considering theory behind these terms, polyvalent means it uses more than one electron in formation of chemical bonds while polyatomic means it uses more than one atom to form an ion.
Summary – Polyvalent Element vs Polyatomic Ion
Basically, the key difference between polyvalent element and polyatomic ion is that polyvalent elements have more than one valency whereas polyatomic ions have more than one atom that are covalently bonded to each other.
Reference:
1. Helmenstine, Anne Marie, Ph.D. “Polyatomic Ion: Definition and Examples.” ThoughtCo, Jan. 12, 2019, Available here.
Image Courtesy:
1. “Nitrate-ion-elpot” By Benjah-bmm27 – Own work (Public Domain) via Commons Wikimedia