Group 15 elements or pnictogens are one of the main members of the p-block elements in the modern periodic table. Questions related to these elements are asked almost every year in JEE. Some FAQs related to group 15 elements are:
Question: What are the general characteristics of group 15 elements?
Answer: Group 15 elements or pnictogens include Nitrogen,Phosphorus,Arsenic, Antimony (Sb), and Bismuth. The elements of Group 15 have a general electronic configuration of “ns2np3” that is, they have five electrons in their outermost shell with half-filled p orbitals. Covalent and ionic radii increase from top to bottom in the group due to increase in the number of shells. However, increase in the covalent radii is quite significant from N to P in comparison to As to Bi due to completely filled d, f orbitals in the heavier members. Ionisation enthalpy decreases down the group assize of the atom increases. Electronegativity generally decreases down the group due to increase in atomic size.
Questions: What are the chemical properties exhibited by group 15 elements?
Answer: The elements of Group 15 exhibit a wide range of oxidation states of which -3, +3 and +5 oxidation states are prominent. The stability of -3 oxidation state decreases down the group due to increase in size and metallic character. The stability of +5 oxidation states decreases down the group whereas +3 oxidation state increases down the group due to inert pair effect. Some prominent reactions of group 15 elements are:
- Reactivity with hydrogen: All the elements of group 15 react with hydrogen to form their respective hydrides of the formula EH3 (where ‘E’ stands for the elements of group 15). The bond strength of H-E bond decreases down the group as a result the basicity of hydridesalsodecreases down the group.
- Reactivity with oxygen: All the elements of group 15 react with oxygen to form oxides of E2O3 type (where ‘E’ stands for group 15 elements). The acidic character of oxides decreases down the group and also the oxides in the higher oxidation state of an element ismore acidic than that of the lower oxidation state.
- Reactivity with halogens: Group 15 elements form a wide range of halides of EX3 type, EX5 type and EX2 type, where E is an element of group 15 and X is a halogen.Pentahalides in general are more covalent than trihalides. Nitrogen does not form pentahalides as it lacks d orbitals. Of all the trihalides of nitrogen only NF3 is found to be stable.
Questions: Which reference books can one follow for group 15 elements?
Answer: While studying group 15 elements for JEE, one must go through the NCERT class 12th chemistry textbook part-1. A brisk walk through NCERT will not only give you a sound idea of the various topics you need to cover according to the JEE syllabus but also develop the fundamentals regarding the topic. Apart from this, you can follow a reference book to understand some concepts which are not elaborately explained in NCERT. J.D. Lee’s book on inorganic chemistry can be used as a reference book. Apart from this you can practice previous year JEE questions and questions from O.P Tandon’s book for inorganic chemistry.
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