The nitrogen family corresponds to group 15 of the periodic table. The constituent elements of this group are also called pnictogens or nitrogenoids. The name pnitogens comes from the Greek word pnigein , which means “to strangle”, referring to the property that nitrogen has to cause suffocation.
As with the remains of groups on the periodic table, the elements that make up a group have an electronic configuration, in addition to following trends that result in easily predictable chemical properties.
The nitrogen group is made up of five elements, which from top to bottom are: nitrogen, phosphorus, arsenic, antimony, and bismuth. There is also talk of the synthetic element called muscovium, whose discovery has been confirmed.
All group 15 elements follow the following general periodic trends:
- Electronegativity is the ability of atoms to attract electrons. Electronegativity decreases as you go down the group.
- Ionization energy refers to the amount of energy it takes to remove an electron from an atom in the gas phase. Ionization energy decreases going down the group.
- The atomic radius increases going down the group.
- Electron affinity is the ability of an atom to accept an electron, and it decreases as you go down the group.
- Metallic character increases going down the group.
- Melting point, which is the amount of energy required to break bonds and change a solid-phase substance to a liquid-phase substance, increases going down the group.
- Boiling point, the amount of energy required to break bonds and change a substance in the liquid phase to a gas, increases in the group.
Elements of group 15
The physical properties of this group vary from one element to another and the metallic character increases as you go down in it.
Nitrogen is a non-metallic element, which has no color, taste and odor, it occurs in nature as a non-combustible gas. When compared with the rest of the group, it presents the highest electronegativity, which makes it the element with the greatest non-metallic character. Its usual oxidation numbers are +5, +3 and -3. It is found in 0.002% in the earth’s crust, while in the atmosphere it corresponds to 78% abundance.
It is found naturally in animal and plant proteins, and in fossil remains of plants. Before it was discovered that ammonia could be obtained from nitrogen, the process known as Harber-Bosch, nitrogen sources were limited. It also highlights its low solubility in water.
Nitrous oxide, also called “laughing gas,” was used in dentistry, in childbirth, and to increase the speed of cars.
Phosphorus is a non-metallic element. The most common oxidation state of phosphorus is -3. It is the element that occupies the 11th position in abundance of the earth’s crust, being 0.11%. The main source of phosphorus. It is usually found as part of minerals, and rarely in a pure form.
Various types can be found in phosphorus, such as white phosphorus, which is a white waxy solid that can be cut with a knife. It forms a tetrahedral molecule, P4. White phosphorus is toxic, while red phosphorus is non-toxic.
Red phosphorus is formed when white phosphorus is heated to 573 Kelvin and not exposed to air. It is less reactive than white phosphorus, and has a polymeric structure like a chain and is more stable. Both white and red phosphorous have been used to make match tips, but white phosphorus is avoided due to its toxicity.
Phosphorus has many applications: Phosphorus trichloride, for example, is used in soaps, detergents, plastics, synthetic nylon rubber, motor oils, insecticides, and herbicides. Phosphoric acid is used in fertilizers, and is also used in the food industry.
Arsenic is a highly poisonous metalloid. Due to its semi-metallic character, it has high density, moderate thermal conductivity and a limited electrical conductive character. The oxidation states of arsenic are +5, +3, +2, +1, and -3. The allotropic forms of arsenic are: yellow, black, and gray, the latter being the most common.
Arsenic-containing compounds are used in insecticides, herbicides, and alloys. Also note that arsenic oxide has an amphoteric character, that is, it can act both as an acid and as a base.
Antimony is also a metalloid, the most common oxidation states of which are +3, -3, and +5. The most stable allotrope of antimony is the metallic form, which has properties similar to those of arsenic: high density, moderate thermal conductivity , and a limited ability to conduct electricity. One of the uses for which antimony stands out is its use as a semiconductor.
Bismuth is a metallic element, whose oxidation states are +3 and +5 points. Bismuth is commonly used in cosmetic products and medicine. It is also the one with the lowest electronegativity and also the lowest ionization energy, which means that it is more likely to lose an electron compared to the rest of the group 15 elements.