Question

Chlorine is an element of atomic number 17. It is a mixture of two isotopes having mass number of 35 and 37.

1. What is meant by “atomic number of an element”? What do you understand by an ‘atom’
2. Write down the electronic configuration of the chlorine atom.
3. State the number of protons, electrons, and neutrons in the following isotopes: ³⁵Cl₁₇, ³⁷Cl₁₇
4. Explain why the two atoms in (iii) above have the same chemical reactions.
5. If molten magnesium chloride is electrolyzed suggest a suitable electrode [anode].

Answer 1

1. Atomic number is the number of protons in an atom.
   Atom: The basic unit of matter is the smallest particle of an element that can take part in a chemical reaction.
2. Number electrons in chlorine atom is 17 [2, 8, 7] and their distribution in various shells in K = 2, L = 8, M = 7.
3. Two isotopes of chlorine are
   ³⁵₁₇Cl number of protons = 17 and number neutrons = 35 – 17 = 18
   Number of electrons = 17
   ³⁷₁₇ Cl number of protons = 17
   electrons = 17
   neutrons = 20 (37 – 17)
4. Two isotopes of chlorine have same chemical reactions as their atomic number i. e. number of electrons i.e. electronic configuration is the same (17).
5. When molten magnesium chloride is electrolyzed suitable anode used is carbon.