. The positions of three elements A, B, and C in the periodic table are shown here


i. State whether A is a metal or non-metal

ii. State whether C is more reactive or less reactive than A

iii. Will C be larger or smaller in size than B

iv. Which type of ion, cation or anion, will be formed by element A

v. What will be the valency of element B

Best Answer


i. Element A is in group 17. Now, group 17 is on the right side of the periodic table where non-metals (called halogens) are placed. So, element A is a non­metal. It is a halogen.      

ii. In group 17 of halogens, the chemical reactivity decreases on going down in a group. Thus, element C will be less reactive than element A.         

iii. On going from left to right in a period, the size of atoms decreases. So, the atom of C will be smaller in size than an atom of B

iv. Element A of group 17 has 17 - 10 = 7 valence electrons. So, it will accept 1 electron to form a negatively charged ion, A-. The negatively charged ion is called an anion. Thus, element A will form an anion.

v. Element B is in group 16 of the periodic table so its atom will have 16 -10= 6 valence electrons. This means that an atom of B requires 2 more electrons to achieve the eight-electron noble gas electron configuration. So, the valency of B will be 2

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