There are several chemical elements that commonly appear red or reddish in color. The most well-known red element is iron, which rusts to a reddish color when exposed to oxygen. Other metallic elements like copper and gold also exhibit reddish tones. Non-metals like sulfur and phosphorus can form red allotropes as well. This article will explore some of the key chemical elements that are red or reddish, looking at their properties and applications.
Iron
Iron is perhaps the most familiar red element. In its pure form, iron appears lustrous gray. However, when iron is exposed to oxygen, it undergoes oxidation and forms rust – hydrated iron oxide. This gives iron a characteristic reddish-brown color. Rusting iron is very common, being found on cast iron pans, steel structures, and more. The chemical reaction for iron rusting is:
4Fe + 3O2 → 2Fe2O3
Iron is an abundant element on Earth, being the fourth most common element in the Earth’s crust. It is also a vital nutrient used by all forms of life. In the human body, iron is a key part of hemoglobin, enabling red blood cells to carry oxygen.
Some key facts about iron:
- Atomic number: 26
- Category: Transition metal
- Density: 7.874 g/cm3
- Melting point: 1538°C
- Boiling point: 2862°C
Iron’s high strength and low cost have made it the world’s most commonly used metal. Alloyed with carbon and other metals, iron is used in steel. Major uses of iron and steel include vehicles, buildings, railways, and all types of machinery and tools. Stainless steel, made by adding chromium to iron, resists rusting and is used for kitchen equipment, appliances, tools, etc.
Copper
Copper is another metallic element with a reddish tone. In its pure form, copper has a reddish-orange color. It is also one of the first metals used by humans, with archaeological evidence of copper use dating back over 10,000 years.
Some key facts about copper:
- Atomic number: 29
- Category: Transition metal
- Density: 8.96 g/cm3
- Melting point: 1084°C
- Boiling point: 2567°C
Copper has excellent electrical and thermal conductivity, second only to silver in this regard. It also has antibacterial properties. Major uses of copper include electrical wiring, plumbing, cookware, currency, and architectural elements. The Statue of Liberty gets its greenish-blue color from the patina formed as copper oxidizes over time.
Gold
Gold is a dense, lustrous metal that has a yellowish yet distinctly reddish tone. It has been considered a precious metal for centuries, being valued especially for currency, jewelry, and decoration.
Some key facts about gold:
- Atomic number: 79
- Category: Transition metal
- Density: 19.3 g/cm3
- Melting point: 1064°C
- Boiling point: 2807°C
Gold is incredibly resistant to tarnishing and corrosion, keeping its luster indefinitely. It is also highly ductile and malleable, being extremely workable into fine wires and sheets. Major uses of gold include jewelry, investment, electronics, dentistry, glassmaking, gilding, and more. The density and rarity of gold make it very valuable.
Sulfur
Sulfur is a non-metallic element that can form several allotropes, some of which are red in color. The most common allotrope is yellow, but red crystalline monoclinic sulfur can also form. Sulfur burns with a blue flame to form sulfur dioxide gas.
Some key facts about sulfur:
- Atomic number: 16
- Category: Non-metal
- Density: 2.07 g/cm3
- Melting point: 115°C
- Boiling point: 445°C
Sulfur has many industrial uses, especially in producing sulfuric acid – one of the world’s most industrially produced chemicals. It is also used in manufacturing phosphate fertilizers, chemicals, dyes, limestone, ores, and more. Elemental sulfur is added to vulcanize natural rubber, enhancing its strength and durability.
Phosphorus
Phosphorus commonly occurs as colorless or yellowish solids, but one of its allotropes is red phosphorus. Red phosphorus is formed by prolonged heating of white phosphorus, which converts it from being reactive and dangerous to stable and safe to handle. Some key facts about phosphorus:
- Atomic number: 15
- Category: Non-metal
- Density: 1.82 g/cm3 (red)
- Melting point: 597°C (red)
- Boiling point: 280°C
Phosphorus is essential for all forms of life as a building block of DNA, RNA, and ATP. Industrially, phosphorus compounds are widely used in fertilizers, food additives, cleaners, phosphorescent paints, pesticides, matchstick heads, and more. Red phosphorus is used in semiconductor doping and incendiary bombs and grenades.
Other Reddish Elements
Some other chemical elements can exhibit reddish colors in certain forms or conditions:
- Chromium: A transition metal that has a silvery white appearance, but chromium(III) oxide is greenish-gray to red in color.
- Manganese: Used as a black pigment as MnO2, but can form pink or red hydrated oxides like Mn(OH)2.
- Mercury: Forms red mercuric oxide (HgO) when heated.
- Rubidium: A soft, silvery alkali metal that burns with a dark red color in air.
- Selenium: Commonly dark gray, but red amorphous selenium allotropes exist.
- Strontium: Burns bright red when ignited in air.
Conclusion
In summary, while no element is fully red, several metals and non-metals exhibit reddish hues. The most iconic red element is iron, which pervasively rusts to a red-brown color. Copper, gold, sulfur, and phosphorus also have important red allotropes or forms. Other elements like chromium, manganese, mercury, rubidium, selenium, and strontium can appear reddish under certain conditions. When seeking red chemical elements, iron, copper and sulfur are good places to start.
| Element | Atomic Number | Category | Density (g/cm3) | Melting Point (°C) | Boiling Point (°C) |
|---|---|---|---|---|---|
| Iron | 26 | Transition metal | 7.874 | 1538 | 2862 |
| Copper | 29 | Transition metal | 8.96 | 1084 | 2567 |
| Gold | 79 | Transition metal | 19.3 | 1064 | 2807 |
| Sulfur | 16 | Non-metal | 2.07 | 115 | 445 |
| Phosphorus (red) | 15 | Non-metal | 1.82 | 597 | 280 |
