The Deadly Element Arsenic


Introduction to Arsenic

Stationed in the non-metals category of the periodic table sits the most deadly element arsenic. It is categorized as a metalloid and is located in group 15. The element appears shiny grey in color. Due to high toxicity, the use of the element is being phased out of production.

Ten Interesting Facts About Arsenic

  • Arsenic can cause a variety of health issues. A large enough dose can cause instant sickness and death. Prolonged exposure to this element may even cause bladder or lung cancer.
  • In the 1980s it was used in rat traps and pesticides because it is such a strong toxin. After several decades of its use in agriculture, farmers realized the health issues this was causing. In the later twentieth-century, the government banned arsenate pesticides.
  • Sometimes (As) is alloyed with lead to form a durable metal. Most times it is found in car batteries and bullets.
  • At regular temperature it is similar to carbon dioxide; instead of melting it sublimes into vapor. Liquid arsenic only occurs naturally under high pressure.
  • Despite the element’s toxic nature. It is an essential nutrient in foods for farm animals. Often times added to the livestock food to aid in weight gain.
  • Good thing for us, earth’s crust rarely contains arsenic. One-third of it is in the atmosphere from volcanoes, but a large portion of it comes from activities such as smelting, mining, and power plants burning fossil fuels. Deepwater wells often contain the element.
  • When it is in its most stable state it is a grey color, it is very brittle, and is a poor conductor of electricity.
  • Weirdly enough, arsenic contributes to the beauty of butterflies. The element creates the green color of butterflies and moths wings.
  • Researchers estimate that arsenic killed more than 100 million people in the last century. Most of these deaths were from contaminated drinking water.
  • Surprisingly, it doesn’t always kill living things. When your soil gets too low in minerals grass begins to die and it won’t grow back unless it’s fertilized. It protects your lawn from droughts.

As on the Periodic Table

Arsenic’s chemical symbol is (As), it can be found in group 15 and period 4 on the periodic table. It has an atomic radius of 1.85 pm and its common oxidation states are 5,3, and -3.

In its neutral form, it has an atomic number of 33, meaning it has 33 protons and neutrons. It is also a metalloid because it exhibits traits of both metals and non-metals. It is most similar to phosphorus.

Arsenic periodic table example

Arsenic Poisoining

Arsenic poisoning is also known as arsenicosis. It usually happens when people or animals ingest or inhale a very high level of the element. It is a carcinogen that is very dangerous to humans. The deadly element goes by many names, one of them being the “silent killer” since it has no odor or smell which makes it extremely dangerous.

This type of illness usually happens to people who work or live in or near industrialization plants. The United States, India, and China are countries with high levels of it in their groundwater. The symptoms of arsenic poising are muscle cramps, abnormal heart rhythm, and red skin. If someone were to experience darkening of the skin or a constant sore throat, they may have had prolonged exposure to it. Smoking tobacco, living near landfills, and breathing in dust from wood can all lead to As poisoning.

There is no cure or exact treatment for this type of poisoning. The more common treatments are vitamin E and selenium supplements to cancel the toxin out.

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Arsenic in Pesticides

In the early 1900s, the United States government supported arsenic pesticides. In a year, about 30 million pounds of lead and calcium arsenate were spread over crops across the country. It was used to preserve wood from rot. Years ago, rat poisons, ant poisons and weed killers contained the compound. Most old agricultural soils have high levels of arsenic from the former pesticides.

Airborne particles of it travel long distances in the air and inhaled. Oftentimes it would tend to stick to the soil but sometimes it can dissolve in water and leak into freshwater sources like lakes. Burning, sanding, or cutting treated wood increases the chance of poisoning. Because of this, the FDA banned pesticides containing arsenic in the late twentieth century.

Arsenic’s Applications in today’s World

What is it Used for?


It can be found in the medication, Arsenic Trioxide, which is often used in conjunction with tretinoin. Ironically enough, the combination treats acute promyelocytic leukemia (APL). When chemotherapy fails, doctors often employ this treatment. It may also be used in patients whose condition was fine but then got worse following treatment with chemotherapy. This medicine works by slowing and hopefully stopping the growth of cancer cells. Like anything dealing with the toxic element, this drug comes with many severe side effects. Side effects include angina, mood changes, and behavior changes similar to having too much alcohol.


Arsenic often resides in wood due to pesticides. Chromated copper arsenate (CCA) preserves the wood. This prevents rotting in wood designed for outdoor use. Anywhere wood exists, you could find wood treated with CCA. Because arsenic is a known carcinogen things like play sets, decks, and picnic tables are receiving the most attention. When it rains or snows in certain regions it can bleed into the soil. This provides another source of exposure for children.

Where is arsenic found?

The naturally occurring element arsenic is often found in combination with other inorganic or organic things to form many different substances. Sediments and soils contain inorganic arsenic compound from pesticides and industrial processes. Sea creatures, like fish and shellfish, oftentimes contain organic arsenic. The amount of the toxin found in seafood is not harmful to humans. China and Morocco mine majority of the arsenic.

When and How was Arsenic Discovered?

Arsenic-based compounds have been around since Ancient Greece and Rome. Doctors used arsenic-based compounds for medicine. And alchemists used the compounds for poison. It was first recognized as an element by a type of scientist called alchemists in 500 B.C. Albertus Magnus (Albert the Great) receives credit for the real discovery of arsenic. He discovered the toxic element by heating a compound of arsenic known as orpiment and mixed it with soap. From this process, he nearly formed the element in its pure form. By the mid-seventeenth century, scientist recognized it as a well-known element.

It derives its name from the Latin word arsenicium and the Greek word arsenikos, meaning “masculine” or “male”. The ancient Greeks thought that metals were of different sexes.

Arsenic Chemistry – Compounds, Reactions, oxidation states

Chemical Properties

Arsenic, in its elemental state, tarnishes rapidly in air, and at high temperatures burns to form a grayish or white cloud of arsenic trioxide. The non-metallic form of arsenic is less reactive but will dissolve with strong acids and alkalis when heated.

Arsenic Compounds

Arsenous Acid

Is an inorganic compound with the formula As(OH)3. Arsenous acid is often amphoteric. It will usually react with hydrochloric, hydrobromic, and hydroiodic acids to produce trichloride, tribromide, and triiodide.

3 HCl + As(OH)3 ⇌ AsCl3 + 3 H2O

As(OH)3 + 3 HBr ⇌ AsBr3 + 3 H2O

3 HI + As(OH)3 ⇌ AsI3 + 3 H2O

Arsenic Acid

This colorless inorganic acid is the analogue of phosphoric acid. It is occasionally used in wood preservatives, and glass finishing agents. However, because of its toxicity people hesitate to use it. Its chemical formula is H3AsO4.

Monomethylarsonous Acid

This organic compound is known to be even more toxic than pure arsenic. Its only roles in real-world applications are as a carcinogenic agent and a poison. Its chemical formula is CH5AsO2.


AsB, or arsenobetaine, is an organoarsenic compound. Arsenic found in fish comes from this compound. Unlike any of the other forms of As, this form is usually non-toxic


Arsenocholine is an arsonium ion that is choline where the central nitrogen atom has been completely replaced by arsenic. C5H14AsO+, main role is as a marine metabolite and a human urinary metabolite

Methylarsonic Acid

Is a member of the arsonic acid family. It is also the conjugate acid of a methylarsonate. Its chemical formula is CH3AsO(OH)2.

Dimethylarsinous acid

C2H7AsO is not commonly used in any real-world scenarios because of its toxicity. It is considered a carcinogen at high doses.

Trimethylarsine oxide

C3H9AsO is a member of the arsine oxides. This is used as a source of arsenic in the microelectronics industry, also a stepping stone to other organoarsenic compounds, and served as a ligand in coordination chemistry. Typically, the resulting arsenic compounds have coordination numbers of either 4 or 6.

Arsenic Trioxide

Arsenic trioxide (As2O3), as mentioned above, treats a range of illnesses such as cancer. It can also treat wood and preservatives.

Physical Properties

Arsenic, symbol As, forms in two allotropic forms. The most common form of it is a lustrous gray, which is very brittle, and it appears to be a metallic looking solid.

The second form, and the less common form, is a yellow crystalline solid. The crystalline solid forms from cooling vapors very quickly. The element does not melt when heated, it will change directly into a gas under a process known as sublimation. Under high-pressure, arsenic melts by force at a temperature of 814°C or 1,500°F. Its density is 5.72 grams per cubic centimeter.

  • Symbol: As
  • Melting point: 1,502°F (816.8°C)
  • Boiling point: 1,135°F (613°C)
  • Density: 5.73 g/cm3
  • Atomic weight: 74.9 u
  • Atomic number: 33
  • Electronegativity: 2.18
  • Classification: Group 15
  • Electron shell configuration: [Ar] 3d¹⁰4s²4p³
  • Isotopes – As has 33 isotopes only one is stable, As-73
  • Found naturally in soils, sediments, and groundwater
  • Toxicity: The arsenic ion is generally very toxic
Picture of arsenic

Chemical Properties

Arsenic is a metalloid, meaning it has properties of both metals and non-metals. These metalloids occur on either side of the zigzag line that runs from boron to aluminum. When arsenic is heated in air, it mixes with oxygen and forms arsenic oxide (AsO). The reaction produces a blue flame and potent garlic-like smell.

Arsenic combines with oxygen a lot slower at room temperature. Arsenic does not dissolve in water or most cold acids.

Where Can I buy Arsenic?

Surprisingly enough, arsenic is available for purchase on pretty much any online retailer. For example, online arsenic trioxide tablets cost $137.65.

Other Fun Facts

  • Can a toxic element really be a key nutrient for development and growth in humans? Evidence suggests that proper growth requires trace amounts of some toxic metals. Scientists have come to the conclusion that the body needs arsenic. To maintain a healthy nervous system, a very small amount of arsenic must be ingested.
  • In 18 B.C. A Roman dictator, Lucius Cornelius, attempted to end an epidemic of arsenic poisonings, by passing the very first law against poisoning, known as the Lex Cornelia.
  • Pigment paintings, fabric, and wallpapwer also contained the deathly element in the past. One of the most popular pigments called Scheele’s green, named after a Swedish chemist who invented it. Copper arsenite formed the bright green hue.
  • In Bangladesh, streams and natural drinking water sources contain large amounts of arsenic. How much of this is lethal? The concentrations of it in the water are around 170 to 1500 micrograms per liter. To put that in perspective a microgram is a millionth of a gram. So, for a fatal poisoning, a person would have to drink more than 80,000 micrograms of arsenic all in a sitting. Exposure over a long period of time to waters like those in Bangladesh can cause a plethora of illnesses.

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