Short Answer TypePredict the formulae of the stable binary compounds that would be formed by the following pairs of elements:
calcium and iodine
Predict the formula of the stable binary compounds which would be formed by the following pairs of elements:
(i) element 114 and fluorine
(ii) element 120 and oxygen.
Long Answer TypeDiscuss briefly the anomalous behviour of elements of second period.
Or
The first element of each group differs significantly from rest of the elements of the same group. Give reasons.
The first element of each of the groups 1 (lithium) and 2 (beryllium) and groups 13-17 (boron to fluorine) differs in many respects from the other members of their respective group. The difference in the behaviour of the first member of a group in the s- and p-block compared to the other members in the same group can be due to the following factors:
(i) Small atomic size of the first element.
(ii) Large charge/radius ratio
(iii) High electronegativity
(iv) The absence of d-orbitals in the valence shell of the first element.
The first member of s- and p-block has only four, valence orbitals (2s and 2p) available for bonding. As a result, the maximum covalency of the first member of each group is 4. On the other hand, the second member of the groups has nine valence orbitals (3s, 3p, 3d). Hence these members can expand their covalency beyond 4, through the participation of d-orbital in bond formation.
(v) Ability to form pπ-pπ multiple bonds. The first member of each group of p-block elements has great tendency to form pπ-pπ multiple bonds to itself (C = C. C ≡ N, N = N, N ≡ N and to the other second period N, N ≡ N) elements (C = 0, C = N, C ≡ N, N = 0).
Short Answer TypeShow by a chemical reaction with water that Na2O is a basic oxide and Cl2O7 is an acidic oxide.
What is the basic difference in approach between the Mendeleev’s Periodic Law and the Modern Periodic Law?
Long Answer TypeOn the basis of quantum numbers, justify that the sixth period of the periodic table should have 32 elements.
Short Answer TypeLong Answer TypeAmong the second period elements the actual ionisation enthalpies are in the order
Li<B<Be<C<O<N<F<Ne.
Explain why
(i) Be has higher 
than B
(ii) O has lower 
than N and F?
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