Nitrogen is required for all forms of life and is a structural component of amino acids, which are used to make animal and human tissues, enzymes, and many hormones. In natural systems, available (fixed) nitrogen is usually the limiting nutrient for plant growth. Because of the number of oxidation states, nitrogen chemistry and overall cycling in the global environment are quite complex. Nitrogen has five valence electrons and can be found in oxidation states ranging from –3 to +5. As a result of chemical, biochemical, geochemical, and biogeochemical processes, numerous species can form.
Definition: Nitrogen has the chemical symbol N and the atomic number 7. Nitrogen is a non-metal and the lightest member of Periodic Table Group 15, also known as the pnictogens.
Nitrogen in Chemistry Questions with Solutions
Q1. The atomic number of nitrogen is:
Correct Answer – (b.) 7
Q2. The symbol for the nitrogen atom is:
Correct Answer – (a.) N
Q3. Two nitrogen atoms are joined by how many covalent bonds?
d.) ionic bond
Correct Answer – (c.) three
Q4. What is the valency of a nitrogen atom?
Correct Answer – (b.) 3
Q5. Nitrogen is a ____.
d.) None of the above
Correct Answer – (b.) non-metal
Q6. What is the electronic configuration of nitrogen?
Answer. The general electronic configuration of nitrogen is 1s2, 2s2, 2p3.
Q7. Is nitrogen gas N or N2?
Answer. Nitrogen has the chemical formula N, but because it exists in a molecule of two ions, the chemical symbol for nitrogen gas is N2.
Q8. How do plants absorb nitrogen?
Answer. Plants cannot absorb nitrogen directly from the atmosphere. Only nitrifying bacteria in soil can convert gaseous nitrogen into nitrites or nitrates. Through their root hairs, plants can absorb nitrate or nitrite from the soil.
Q9. Where is nitrogen found?
Answer. Nitrogen can be found in the soil, water and air. Nitrogen is the most abundant element in the Earth’s atmosphere, accounting for approximately 78% of the total.
Q10. What is the position of nitrogen element in the periodic table?
Answer. Nitrogen (N) has an atomic number 7, which indicates that it is placed in the second period and 15th group.
Q11. State the properties of nitrogen.
Answer. The physical properties of nitrogen are as follows:
- It is generally inert.
- It is non–metallic.
- It is colourless.
- It is odourless.
- It is tasteless.
- It exists as a diatomic gas.
- Its atomic number is 7.
- It has an atomic weight of 14.0067.
- Nitrogen is slightly lighter than air.
Q12. What is nitrogen fixation?
Answer. Nitrogen fixation is a necessary biological process that occurs at the beginning of the nitrogen cycle. Nitrogen in the atmosphere is converted into ammonia (another form of nitrogen) in this process by certain bacterial species such as Rhizobium, Azotobacter, and others, as well as by natural phenomena.
Q13. What are the uses of nitrogen gas?
Answer. Some of the uses of nitrogen are as follows:
- Nitrogen gas is used to create an unreactive environment, which protects foods from degradation.
- Nitrogen is used in some aircraft fuel systems to reduce fire hazards.
- The chemical industry also relies on nitrogen. It is used to make fertilisers, nitric acid, nylon, dyes, and explosives.
- Since nitrogen is a non-reactive gas, it is used to fill light bulbs.
- Nitrogen is frequently used in the pharmaceutical industry to transfer a reaction mixture from one vessel to another.
Q14. Discuss some laboratory methods to obtain nitrogen.
Answer. There are several methods for preparing nitrogen from its compounds in the laboratory on a small scale.
- A hot aqueous solution of ammonium nitrite spontaneously decomposes to yield elemental nitrogen and water.
- Heating barium or sodium azide (NaN3 or Ba[N3]2) produces free nitrogen as well.
- When ammonia gas is passed over a hot metallic oxide, free nitrogen, free metal and water are formed.
- The reaction between ammonia and bromine produces nitrogen and ammonium bromide.
Q15. Describe the nitrogen cycle.
Answer. The nitrogen cycle is a biogeochemical process in which nitrogen is converted into various forms before passing from the atmosphere to the soil to the organism and back into the atmosphere.
It involves several processes such as nitrogen fixation, nitrification, denitrification, decay and putrefaction.
- Nitrogen Fixation – The nitrogen cycle begins with this step. This step is characterised by the conversion of atmospheric N2 into ammonia (NH3). Bacteria such as Azotobacter and Rhizobium play an important role in this process. They live in the roots of leguminous plants and aid in the conversion of inert nitrogen to ammonia.
- Assimilation – Plants use their roots to absorb nitrogen compounds from the soil, which are available in the form of ammonia, nitrite ions, nitrate ions or ammonium ions and are used in the formation of plant and animal proteins. When the primary consumers eat the plants, it enters the food web.
- Ammonification – When plants or animals die, the nitrogen in the organic matter returns to the soil. Organic matter is converted back into ammonium by decomposers, which are bacteria or fungi found in the soil. This decomposition process generates ammonia, which is then used in other biological processes.
- Nitrification – The presence of bacteria in the soil converts ammonia to nitrate during this process. Nitrites are formed through the oxidation of ammonia by Nitrosomonas bacteria species. Nitrobacter then converts the nitrites produced into nitrates. This conversion is critical because ammonia gas is toxic to plants.
- Denitrification – Denitrification is the process by which nitrogen compounds return to the atmosphere after being converted from nitrate (NO3–) to gaseous nitrogen (N). This is the final stage of the nitrogen cycle and occurs in the absence of oxygen. The denitrifying bacterial species Clostridium and Pseudomonas are responsible for denitrification.
Practice Questions on Nitrogen
Q1. Nitrogen forms a ____.
c.) both cation and anion
d.) none of the above
Q2. The correct electronic configuration of nitrogen is _____.
a.) 2, 7
b.) 2, 5
c.) 2, 8, 5
d.) none of the above
Q3. How can nitrogen be separated from the air?
Q4. What is the importance of the nitrogen cycle?
Q5. What is liquid nitrogen?
Click the PDF to check the answers for Practice Questions.