Nitrogen (atomic number 7) and phosphorus (atomic number 15) belong to group 15 of the periodic table. Write the electronic configurations of these two elements. Which of these will be more electronegative ? Why?

On moving from left to right in a period of the periodic table, the atomic number of elements increases. What happens to the size of atoms of elements on moving from left to right in a period?

The atomic numbers of the elements Na, Mg, K and Ca are 11, 12, 19 and 20 respectively. The elements having the largest atomic radius is:

The element which can form an acidic oxide should be the one whose atomic number is:

An atom has the electron structure of 2, 7.

(a) What is the atomic number of this atoms?

(b) To which of the following would it be chemically similar?

₇N, ₁₅P, ₁₇Cl, ₁₈Ar

(c) Why would you expect it to be similar?

In each of the following pairs, choose the atom having the bigger size:

(a) Mg (At. No. 12) or Cl( At. No. 17)

(b) Na (At. N0. 11) or K (At. No. 19)

Consider the following elements:

₂₀Ca, ₈O, ₁₈Ar, ₁₆S, ₄Be, ₂He

Which of the above elements would you expect to be:

(i) Very stable?

(ii) In group 2 of the periodic table?

(iii) In group 16 of the periodic table?

Which of the following set of elements is written correctly in the order of their increasing metallic character?

Which one of the following does not increase while moving down the group of the periodic table?

The element which forms a basic oxide has the atomic number of:

The atomic numbers of three elements A, B and C are given below:

(i) Which element belongs to group 18?

(ii) Which element belongs to group 15?

(iii) Which element belongs to group 13?

(iv) To which period/periods do these elements belongs?