What is the Difference Between Arsenic 3 and Arsenic 5

The key difference between arsenic 3 and arsenic 5 is that arsenic 3 or arsenite is more toxic than arsenic 5 or arsenate.

Arsenic is often considered a toxic chemical element. It can be found in various different compounds, specifically minerals. Arsenic 3 or arsenite is a chemical species consisting of an arsenic oxyanion in which the oxidation state of arsenic is +3. Arsenic 5 or arsenate is any chemical compound having arsenic-5 oxyanion.

CONTENTS

1. Overview and Key Difference
2. What is Arsenic 3  (Arsenite)
3. What is Arsenic 5 (Arsenate)
4. Arsenic 3 vs Arsenic 5 in Tabular Form
5. Summary – Arsenic 3 vs Arsenic 5 

What is Arsenic 3 (Arsenite)?

Arsenic 3 or arsenite is a chemical species consisting of an arsenic oxyanion in which the oxidation state of arsenic is +3. The field of groundwater chemistry uses arsenite as the indication of arsenic 3 presence in the groundwater. According to IUPAC guides, arsenite compounds are named arsenate(III), e.g. ortho-arsenite is named trioxidoarsenate(III). Ortho-arsenite contains corresponding anions of the lighter members of group 15, such as phosphite and nitrite.

We can prepare some salts of arsenite from the aqueous solution of As₂O₃. For example, meta-arsenite salts, hydrogen arsenite salts, etc. Moreover, there are many different minerals consisting of arsenic 3, such as reinerite, finnemanite, paulmooreite, and stenhuggarite.

There are some important uses of arsenic 3, such as its use in water gas shift reactions in removing carbon dioxide. Furthermore, some bacterial species are able to obtain energy by oxidizing various fuels while reducing arsenates in the formation of arsenites. This process is involved in some reactions containing enzymes known as arsenate reductases.

What is Arsenic 5 (Arsenate)?

Arsenic 5 or arsenate is any chemical compound having arsenic-5 oxyanion. The arsenate anion has an arsenic atom in +5 oxidation state. It is also known as pentavalent arsenic or As(V). Moreover, arsenate resembles phosphate in many aspects because arsenic and phosphorous can occur in the same group of the periodic table. Arsenic-5 compounds are moderate oxidizers having an electrode potential of +0.56 V for the reduction of arsenites.

Naturally, arsenic 5 occurs in minerals consisting of hydrated or anhydrous arsenates. Different from phosphates, arsenates do not get lost from a mineral during the weathering process. For instance, adamite, alarsite, annabergite, erythrite, etc., contain arsenic 5.

In the process of arsenic poisoning, arsenate can replace inorganic phosphate in the glycolysis cycle, which yields 1-arseno-3-phosphoglycerate. This compound is unstable and quickly hydrolyzes to form the next intermediate in the same pathway. This makes the glycolysis proceed, but an ATP molecule is not generated. This explains the toxicity of arsenic 5.

What is the Difference Between Arsenic 3 and Arsenic 5?

Arsenic is an important chemical element that is often considered to be toxic. Arsenic 3 or arsenite is a chemical species consisting of an arsenic oxyanion in which the oxidation state of arsenic is +3. Arsenic 5 or arsenate is any chemical compound having arsenic-5 oxyanion. The most common oxidation states of arsenic are +3 and +5 oxidation states. Moreover, the key difference between arsenic 3 and arsenic 5 is that arsenic 3 or arsenite is more toxic than arsenic 5 or arsenate.

The below infographic presents the differences between arsenic 3 and arsenic 5 in tabular form for side-by-side comparison.

Summary – Arsenic 3 vs Arsenic 5

Arsenic 3 or arsenite is a chemical species consisting of an arsenic oxyanion in which the oxidation state of arsenic is +3. Arsenic 5 or arsenate is any chemical compound having arsenic-5 oxyanion. The key difference between arsenic 3 and arsenic 5 is that arsenic 3 is more toxic than arsenic 5.

Reference:

1. “Arsenic.” Wikipedia. Wikipedia Foundation.
2. “Arsenic(3+).” PubChem. NIH – National Library of Medicine, National Center for Biotechnology Information.

Image Courtesy:

1. “Sodium meta-arsenite” By Claudio Pistilli — Travail personnel (CC BY-SA 4.0) via Commons Wikimedia
2. “Arsenate ion” By Ed (Edgar181) – Own work (Public Domain) via Commons Wikimedia