Chemistry – NITROGEN FAMILY

Chemistry SS 2 Week 4

Topic: Nitrogen Family

Introduction

The nitrogen family includes the following compounds: nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), and bismuth (Bi).

All Group 5 elements have the electron configuration ns²np³ in their outer shell, where n is equal to the principal quantum number. The nitrogen family is located in the p-block in Group 5, having 5 electrons in their outer energy level. As you move down the nitrogen family: atomic radius increases, ionic radius increases, ionization energy decreases, and electronegativity decreases. Nitrogen family elements often form covalent compounds, usually with the oxidation numbers +3 or +5. Nitrogen and phosphorus are non-metals, Arsenic and Antimony are metalloids, while Bismuth is a metal

Properties of Group 5 Elements

Element/Symbol	Atomic Number	Mass	Electron Configuration	Covalent Radius(pm)	Electronegativity	First Ionizaton Energy (kJ/mol)	Common Physical Form(s)
Nitrogen (N)	7	14.01	1s2 2s2 2p3	75	3.0	1402	Colorless Gas
Phosphorus (P)	15	30.97	[fusion_builder_container hundred_percent=”yes” overflow=”visible”][fusion_builder_row][fusion_builder_column type=”1_1″ background_position=”left top” background_color=”” border_size=”” border_color=”” border_style=”solid” spacing=”yes” background_image=”” background_repeat=”no-repeat” padding=”” margin_top=”0px” margin_bottom=”0px” class=”” id=”” animation_type=”” animation_speed=”0.3″ animation_direction=”left” hide_on_mobile=”no” center_content=”no” min_height=”none”][Ne]3s2 3p3	110	2.1	1012	White Solid / Red Solid
Arsenic (As)	33	74.92	[Ar] 3d10 4s2 4p3	121	2.0	947	Yellow Solid / Gray Solid
Antimony (Sb)	51	121.76	[Kr] 4d10 5s2 5p3	140	1.9	834	Yellow Solid / Silver-White Metallic Solid
Bismuth (Bi)	83	208.98	[Xe] 4f14 5d10 6s2 6p3	155	1.9	703	Pink-White Metallic Solid

Nitrogen

Daniel Rutherford, a Scottish Physician, discovered Nitrogen in 1772. But it was Lavoisier, who proved that nitrogen is an element and that it was not a supporter of combustion and respiration. He called it ‘azote’ meaning ‘no life’. The name ‘Nitrogen’ was given to it by Jean Antoine Chaptal (1756 – 1832), in the year 1790. Nitrogen is a chemical element with symbol N and atomic number 7. It is the lightest pnictogen and at room temperature, it is a transparent, odorless diatomic gas. Nitrogen is a common element in the universe, estimated at about seventh in total abundance in the Milky Way and the Solar System. On Earth, the element forms about 78% of Earth’s atmosphere and is the most abundant uncombined element.Nitrogen occurs in all organisms, primarily in amino acids (and thus proteins), in the nucleic acids (DNA and RNA) and in the energy transfer molecule adenosine triphosphate. The human body contains about 3% by mass of nitrogen, the fourth most abundant element in the body after oxygen, carbon, and hydrogen. The nitrogen cycle describes movement of the element from the air, into the biosphere and organic compounds, then back into the atmosphere.

Occurrence of Nitrogen

Nitrogen exists in the free state and in combined form in the atmosphere of the earth. In the free state it occurs as N₂ and occupies about 80% by volume of air. In the combined form, it is present as ammonia and all ammonium compounds, in nitric acid and in all nitrates, nitrites and in all living things in the form of proteins.

Industrial Preparation (large scale)

Industrially, Nitrogen is prepared by fractional distillation; Oxygen is obtained at the same time. Air is purified by removing gas from it.
Then carbondioxide is removed and lastly water vapour. The remaining air is removed and compressed. The liquified air is allowed to evaporate. Because Nitrogen has a lower boiling point, it evaporates first leaving liquid oxygen.

Laboratory Preparation of Nitrogen

Preparation of Nitrogen from Air

Nitrogen is prepared from the air by removing oxygen and carbon dioxide. Water is used to push air through sodium hydroxide solution (caustic soda solution) which removes carbon dioxide.

2NaOH (ag) + CO₂ (g) Na₂CO₃ (g) + H₂O (i)

The remaining gas is passed over heated copper turnings to remove Oxygen.

2Cu (s) + O₂ (g)2CuO (s)

Nitrogen is collected over water as it is insoluble in water.

Preparation of Nitrogen from Chemical Compounds

• By treating excess ammonia with chlorine, ammonium chloride and nitrogen are formed.

• Nitrogen can also be prepared by b heating a mixture of ammonium chloride and sodium dioxonitrate (III).

NaNO₂ (s) + NH₄Cl (s) NH₄NO₂ (s) +NaCl (s)

• Nitrogen is formed by decomposition of ammonium dioxonitrate (III)

NH₄NO₂ (s)N₂ (g) + 2H₂O (i)

Physical Properties of Nitrogen

1. it is colourless gas without smell
2. it is a reactive gas
3. it does not burn / doesn’t support combustion
4. it is neither acidic nor basic
5. Density of nitrogen is 1.25 x 10^-3 g.cm^-3 at 20°C
6. Melting point of nitrogen is -210 °C
7. Boiling point of nitrogen is -195.8 °C

Chemical Properties of Nitrogen

• Nitrogen does not easily combine with other elements under ordinary conditions. A molecule of nitrogen is diatomic. These two atoms have combined by mutually sharing three pairs of electrons.
• Nitrogen is inert unlike Oxygen, it reacts under special conditions for example, It reacts with some metals at very high temperatures forming nitrides e.g. Calcium and magnesium.

            3Mg (s) + N₂(g)Mg₃N₂(s)

3Ca (s) + N₂ (g) Ca₃N₂ (s)

• It forms nitric oxide and nitrogen dioxide with oxygen
• Its reacts with hydrogen to give ammonia

Other Properties of Nitrogen

• Atomic number (number of protons in the nucleus): 7
• Atomic symbol (on the Periodic Table of Elements): N
• Atomic weight (average mass of the atom): 14.0067
• Density: 0.0012506 grams per cubic centimeter
• Phase at room temperature: Gas
• Melting point: minus 321 degrees Fahrenheit (minus 210 degrees Celsius)
• Boiling point: minus 320.42 F (minus 195.79 C)
• Number of isotopes (atoms of the same element with a different number of neutrons): 16 including 2 stable ones
• Most common isotopes: Nitrogen-14 (Abundance: 99.63 percent)

Uses of Nitrogen

1. Nitrogen is used in high temperature thermometers where mercury cannot be used.
2. Nitrogen is used in the manufacture of ammonia, trioxonitrate (V) acid, trioxonitrate (V) salt and fertilizer. Nitrogen is important to the chemical industry. It is used to make fertilisers, nitric acid, nylon, dyes and explosives. To make these products, nitrogen must first be reacted with hydrogen to produce ammonia. This is done by the Haber process. 
3. Liquid nitrogen is used as refrigerant and also used to shrink metal parts that are to be fitted inside other parts. It is used for storing sperm, eggs and other cells for medical research and reproductive technology. It is also used to rapidly freeze foods, helping them to maintain moisture, colour, flavour and texture.
4. Liquid nitrogen is also used in grinding substances that are too tough or too sticky to grind at normal temperature, including drugs, cosmetics and plastics.
5. Nitrogen gas is also used to provide an unreactive atmosphere. It is used in this way to preserve foods, and in the electronics industry during the production of transistors and diodes. Large quantities of nitrogen are used in annealing stainless steel and other steel mill products. Annealing is a heat treatment that makes steel easier to work.
   

Biological Uses of Nitrogen

1. Nitrogen is cycled naturally by living organisms through the ‘nitrogen cycle’. It is taken up by green plants and algae as nitrates, and used to build up the bases needed to construct DNA, RNA and all amino acids. Amino acids are the building blocks of proteins.
2. Animals obtain their nitrogen by consuming other living things. They digest the proteins and DNA into their constituent bases and amino acids, reforming them for their own use.
3. Microbes in the soil convert the nitrogen compounds back to nitrates for the plants to re-use. The nitrate supply is also replenished by nitrogen-fixing bacteria that ‘fix’ nitrogen directly from the atmosphere.
4. Crop yields can be greatly increased by adding chemical fertilisers to the soil, manufactured from ammonia. If used carelessly the fertiliser can leach out of the soil into rivers and lakes, causing algae to grow rapidly. This can block out light preventing photosynthesis. The dissolved oxygen soon gets used up and the river or lake dies.

Applications of Nitrogen Gas

Nitrogen gas has a variety of applications, including serving as an inert replacement for air where oxidation is undesirable;

• As a modified atmosphere, pure or mixed with carbon dioxide, to nitrogenate and preserve the freshness of packaged or bulk foods (by delaying rancidity and other forms of oxidative damage). Pure nitrogen as food additive is labeled in the European Union with the E number E941.
• In some aircraft fuel systems to reduce fire hazard.
• In incandescent light bulbs as an inexpensive alternative to argon.
• Dried and pressurized, it is used as an dielectric gas for high voltage equipment.
• In packaging liquid explosives as a safety measure.
• In fire suppression systems for Information technology (IT) equipment
• In photolithography in deep ultraviolet, nitrogen is used to avoid the strong oxygen absorption of UV at these wavelengths.
• To inflate race car and aircraft tires, reducing the problems caused by moisture and oxygen in natural air.
• In the manufacture of stainless steel.

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