What is the Difference Between Arsenic and Arsenate: An Insightful Comparison

When it comes to common chemical compounds, most of us may have heard about arsenic and arsenate. But have you ever wondered what the difference is between these two? Is there really any difference, or are they the same? In this article, we’ll be diving headfirst into the world of chemistry to explore the differences between arsenic and arsenate.

To begin with, let’s consider what arsenic is. Arsenic is a naturally occurring element in the earth’s crust. It’s a semi-metal that has been found in various forms, such as a pure element and various compounds. The compounds of arsenic are used in a variety of industries, such as wood preservation and electronic manufacturing. On the other hand, arsenate is the oxidized form of arsenic that usually exists in combination with other minerals like iron and copper.

Now you might be wondering what sets the two apart from one another. The main difference between arsenic and arsenate is their oxidation state. Arsenic is a semi-metal that has a zero oxidation state, whereas arsenate has multiple oxidation states, typically of +3 and +5. Additionally, since arsenic is in its elemental or zero oxidation state, it’s typically found in its elemental form or in compounds like arsenide, which is the chemical species of arsenic. On the other hand, arsenate is typically found in minerals as an oxyanion, which is a combination of oxygen and an anion of another element. So, now that we have a basic understanding of the differences between arsenic and arsenate, let’s dive a little deeper into their properties and applications.

Arsenic Definition

Arsenic, a chemical element with the symbol As and atomic number 33, is a toxic metalloid and a member of the group of pnictogens (elements in group 15 of the periodic table). Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. It is widely distributed in the Earth’s crust, and it is found in minerals, soil, water, and air. Humans are exposed to arsenic mainly through food, water, and air, and chronic exposure to arsenic can cause cancer, skin lesions, and other health problems.

Arsenic is known to exist in two main forms in nature:

  • Elemental arsenic, a gray metallic solid
  • Various inorganic and organic forms of arsenic compounds

Inorganic arsenic compounds are generally more toxic than organic compounds. The toxicity of arsenic compounds depends on the oxidation state of the arsenic atom, which can be either trivalent or pentavalent. The trivalent form, also known as arsenious acid or arsenite, is more toxic than the pentavalent form, also known as arsenic acid or arsenate. Arsenite is known to inhibit enzymes that play key roles in cellular respiration, while arsenate can replace phosphate in cellular processes, leading to disruption of cellular energy metabolism.

Arsenate definition

Arsenate is the compound that forms when arsenic reacts with oxygen and other elements such as hydrogen, potassium, or sodium. This compound has a negative charge and can replace phosphate in biological systems, leading to potentially harmful effects on human health. Arsenate can exist in different forms such as monovalent arsenate (H2AsO4-) or divalent arsenate (HAsO4^2-).

  • Arsenate is commonly found in contaminated soil and water, as well as in some pesticides, herbicides, and wood preservatives.
  • Human exposure to arsenate can occur through ingestion, inhalation, or skin contact.
  • Arsenate toxicity can cause various health problems such as skin lesions, cancer, diabetes, cardiovascular diseases, and neurological disorders.

Arsenate is a more stable form of arsenic compared to arsenite, which is the reduced form of arsenic. Arsenate is less toxic but more mobile and water-soluble, making it easier to accumulate in groundwater and affect larger populations. Therefore, arsenate contamination in drinking water sources is considered a serious public health issue in many parts of the world.

Arsenate properties Values
Molecular weight 138 g/mol
Solubility Highly soluble in water
Chemical formula AsO4^-3
Potential health effects Skin lesions, cancer, cardiovascular diseases, neurological disorders, etc.

To prevent arsenate exposure, it is essential to monitor the quality of drinking water sources and to use protective measures when handling potential sources of contamination. Furthermore, treating arsenate-contaminated water with appropriate technologies like reverse osmosis, distillation, or activated alumina can help reduce exposure and improve water quality.

Chemical Properties of Arsenic and Arsenate

Arsenic and arsenate are two closely related chemical compounds that share several similarities in their chemical properties but also have significant differences. Arsenic is a chemical element with the symbol As and atomic number 33. It is a toxic metalloid that occurs naturally in various minerals, rocks, and soils. On the other hand, arsenate is an anionic form of arsenic that contains four oxygen atoms and one arsenic atom and has the formula AsO4 3−.

Arsenic and arsenate share some common chemical properties:

  • Both arsenic and arsenate are toxic substances that can cause health problems when ingested or inhaled.
  • They both have a high affinity for sulfur-containing amino acids like cysteine and methionine.
  • Both can form covalent and ionic bonds with other elements, including heavy metals like lead and mercury.

However, there are also distinct differences in their chemical properties that set them apart:

Arsenic has a metallic appearance and is a good electrical conductor, while arsenate is a non-metallic, anionic compound that does not conduct electricity.

Arsenate is highly soluble in water and can form weakly acidic solutions, while arsenic can form oxides, halides, and sulfides of varying solubility in water.

Arsenic has three oxidation states, which are 0, +3, and +5, while arsenate only has one oxidation state, which is +5. Arsenic can reduce to another toxic form, arsenite (AsO3 3−), which only has one oxidation state, +3.

In summary, arsenic and arsenate have many similarities in their chemical properties, but there are also significant differences between them that make them separate chemical entities. Knowing these differences is essential in understanding their toxicological effects, environmental fate, and industrial applications.

Biological Effects of Arsenic and Arsenate

When it comes to the biological effects of arsenic and arsenate, there are some notable differences between the two. In short, arsenic is much more toxic than arsenate, which is why it has been linked to a wide range of adverse effects on human health and the environment. Here’s a closer look at their biological effects:

  • Arsenic can cause skin lesions, peripheral neuropathy, and cancer, particularly of the lung, bladder, and skin.
  • Arsenic exposure has also been linked to cardiovascular disease, diabetes, and developmental effects in children, including reduced IQ and stunted growth.
  • Arsenic is also known to disrupt cellular metabolism, interfere with DNA repair, and inhibit cellular energy production, all of which can have serious consequences for human health.
  • Arsenate, on the other hand, is less toxic and has been used for many years as a herbicide and insecticide. However, recent research has suggested that it may still have adverse effects on human health, particularly in areas where exposure is high.
  • Arsenate can cause vomiting, diarrhea, and abdominal pain, and has been linked to increased risk of cancer and developmental effects.

Overall, it’s clear that both arsenic and arsenate can have serious effects on human health and the environment. It’s important for scientists and policymakers to continue studying these substances and their effects, in order to better understand and mitigate their impact.

In fact, one recent study found that exposure to low levels of arsenic in drinking water can still have significant health effects, particularly on pregnant women and their babies. This is a powerful reminder of the importance of monitoring and regulating exposure to these substances, to protect public health and the environment.


Arsenic and arsenate are two closely related substances with very different biological effects. While arsenic is highly toxic and has been linked to a wide range of adverse health effects, arsenate is less toxic but still has potential health impacts. It’s important for scientists and policymakers to continue studying these substances, in order to better understand and mitigate their impact on human health and the environment.

Arsenic Arsenate
Highly toxic Less toxic, but still potentially harmful
Linked to skin lesions, neuropathy, cancer, cardiovascular disease, diabetes, and developmental effects like reduced IQ and stunted growth Linked to vomiting, diarrhea, abdominal pain, increased risk of cancer, and developmental effects
Disrupts cellular metabolism, interferes with DNA repair, and inhibits cellular energy production Used as a herbicide and insecticide, but may still have adverse effects on human health

Together, we can work to better understand these substances and their effects, and take steps to protect ourselves and the world around us from their harmful impacts.

Sources of exposure to arsenic and arsenate

Arsenic is a naturally occurring element found in rocks and soil. It can be released into the environment through natural processes such as erosion of rocks, volcanic activity, and forest fires. However, human activities such as mining, smelting, and coal combustion have also contributed to the release of arsenic into the environment. Arsenic can be found in groundwater, which is a primary source of drinking water for millions of people worldwide.

Arsenate is a form of arsenic that is commonly used as a pesticide and herbicide. It is also used in wood preservatives, animal feed additives, and some medical treatments.

Sources of exposure to arsenic and arsenate

  • Ingestion of contaminated water sources: Arsenic can contaminate water sources, particularly groundwater, through natural processes or human activities.
  • Consuming food with high levels of arsenic: Arsenic can accumulate in plants, particularly rice and other grains.
  • Breathing in contaminated air: Arsenic can be released into the air during mining and smelting activities. People who live near these areas may breathe in arsenic-contaminated dust or smoke.

Sources of exposure to arsenic and arsenate

Exposure to arsenic and arsenate can have serious health effects, including skin lesions, cancers of the bladder, lung, and skin, cardiovascular disease, and neurological effects. The risk of exposure is highest for people who live in areas with contaminated water sources or work in industries that involve arsenic exposure.

Reducing exposure to arsenic and arsenate can involve a combination of strategies such as drinking filtered water, avoiding or limiting consumption of foods with high levels of arsenic, using protective equipment in workplaces where arsenic exposure is a risk, and implementing regulations to limit arsenic levels in products and the environment.

Sources of exposure to arsenic and arsenate

Here is a table showing the maximum contaminant levels (MCL) set by the Environmental Protection Agency (EPA) for arsenic in drinking water:

Water Source Arsenic MCL
Public Water Systems 10 micrograms per liter (µg/L)
Individual Water Systems 10 µg/L

It is important to note that some states may have stricter regulations for arsenic levels in drinking water.

Environmental impact of arsenic and arsenate

Arsenic and arsenate are both toxic substances that have harmful effects on the environment. Their presence in soil, water, and air can have severe consequences on living organisms. Here’s a breakdown of their environmental impacts:

  • Arsenic and arsenate in soil can lead to contaminated crops that can’t be consumed. This can hit small farming communities hard since they primarily rely on the income from selling their crop yields.
  • The degradation of groundwater from arsenic and arsenate creates an additional problem. The contaminated water becomes undrinkable and leads to long-term risks of cancer, neuropathy, and cardiovascular disease.
  • The presence of arsenic and arsenate in the air can also be hazardous in industrial settings. The inhalation of these toxins can lead to respiratory diseases and lung cancer.

To better understand the impact of arsenic and arsenate on the environment, let’s look at the table below, which shows the concentration level of arsenic and arsenate in different areas:

Area Arsenic Concentration (mg/kg) Arsenate Concentration (mg/kg)
Contaminated Soil 50-200 27-48
Water Supply 0.01-90 0.01-53
Air Pollution (Industrial settings) 1-1000 N/A

It’s evident that both arsenic and arsenate directly impact the environment in a multitude of ways. The Environmental Protection Agency (EPA) has put several regulations in place to prevent the harmful effects of arsenic and arsenate on the environment. It’s crucial to work together as a community to implement and enforce these regulations to protect the environment and its inhabitants.

Remediation methods for arsenic and arsenate contamination

Arsenic and arsenate contamination is a growing concern all over the world, especially in developing countries with poor waste management systems and inadequate infrastructure to handle toxic waste. Arsenic and arsenate are both highly toxic and can cause several health problems, including skin lesions, cancer, cardiovascular disease, and developmental effects. Remediation methods for arsenic and arsenate contamination aim to mitigate the risk of exposure to these toxic substances and to restore the affected sites to safe conditions.

  • Excavation and disposal: This method involves digging up the contaminated soil and disposing of it in a landfill designed to contain toxic waste. Excavation and disposal are effective for small sites with shallow contamination levels. It is a costly method and can have long-term environmental impacts.
  • Chemical Treatment: Chemical treatments involve adding chemicals to the contaminated soil or water to reduce the concentration of arsenic and arsenate. The most commonly used chemicals are iron salts, lime, and activated carbon. These chemicals react with arsenic and arsenate to form solid precipitates that can be easily separated from the water or soil.
  • Phytoremediation: Phytoremediation is a green technology that uses plants to remove contaminants from soil and water. Plants absorb arsenic and arsenate through their roots and translocate it to their shoots and leaves, where it can be harvested and disposed of. This method is cost-effective and has low environmental impacts. However, not all plants can tolerate high levels of arsenic and arsenate, and the effectiveness of phytoremediation can vary depending on the site conditions.

Another important aspect of remediation methods for arsenic and arsenate contamination is the management of wastewater from treatment processes. The wastewater generated during chemical treatment and phytoremediation can contain high concentrations of arsenic and arsenate, and it needs to be treated before it is released into the environment. The most commonly used methods for treating wastewater from arsenic and arsenate remediation are reverse osmosis, adsorption, and ion exchange.

Remediation Method Advantages Disadvantages
Excavation and Disposal Effective for small sites with shallow contamination levels Costly and can have long-term environmental impacts
Chemical Treatment Can be done in-situ, lower cost than excavation and disposal May create secondary waste, treatment chemicals can have harmful effects
Phytoremediation Cost-effective, low environmental impacts, green technology Not all plants tolerate high levels of arsenic and arsenate, effectiveness varies depending on site conditions

Remediation methods for arsenic and arsenate contamination are still being developed and refined, as the scope and extent of contamination continue to increase. Effective remediation requires a thorough understanding of the site conditions, the type and concentration of contaminants, and the potential environmental impacts of the remediation process itself. It is crucial to employ appropriate measures to prevent the release of arsenic and arsenate into the environment, and to ensure that the treated sites are safe for human and ecological health.

What is the difference between arsenic and arsenate?

1. What is arsenic?
Arsenic is a toxic chemical element that is naturally present in the Earth’s crust and can be found in soil, water, and air.

2. What is arsenate?
Arsenate is a compound that contains arsenic. It is formed when arsenic combines with oxygen and other elements, such as hydrogen, sodium, or calcium.

3. How do arsenic and arsenate differ?
Arsenic is an element, while arsenate is a compound that contains arsenic. Arsenic is pure and has no other elements attached to it, while arsenate is a combination of arsenic and other elements.

4. What are the uses of arsenic and arsenate?
Arsenic has been used in many products, including pesticides, wood preservatives, and some types of medicine. Arsenate is used in fertilizers and as an insecticide.

5. Is arsenic or arsenate more toxic?
Arsenic is more toxic than arsenate because it is a pure element, which means it is more readily absorbed by the body. Arsenate is less toxic because it is a compound and is less readily absorbed by the body.


Now that you know the difference between arsenic and arsenate, you can better understand their properties, uses, and potential environmental and health risks. If you have any further questions, do not hesitate to ask. Thanks for reading and we hope to see you again soon!