13. Assignments

Anomalous Behavior of Beryllium

The properties of beryllium the first member of the alkaline earth metal, differ from the rest of the member. Its is mainly because of

(i)     Its small size and high polarizing power.

(ii)    Relatively high electro negativity and ionization energy as compared to other members.

(iii)    Absence of vacant d – orbitals in its valence shell.

       

Some important points of difference between beryllium and other members (especially magnesium) are given below:   

             

(i)     Be is harder than other members of its group.

(ii)    Be is lighter than Mg.

(iii)    Its melting and boiling points are higher than those of Mg & other members.

(iv)   Be does not react with water while Mg reacts with boiling water.

(v)    BeO is amphoteric while MgO is weakly basic.

(vi)   Be forms covalent compounds whereas other members form ionic compounds.

ASSIGNMENT # 1  

Periodic classification of element

1.Write the outer electronic configuration for the

a)      Alkali metals

b)      Alkaline Earth metals

c)       Halogens

d)      Noble gases

2.Group the following electron configuration in pair that would represent similar chemical properties of their atoms:

a)      1s²,2s²,2p⁶,3s²

b)      1s²,2s²,2p³

c)       1s²,2s²,2p⁶,3s²,3P⁶,4S²,3d¹⁰,4p⁶

d)      1s²,2s²

e)      1s²,2s²,2p⁶

f)       1s²,2s²,2p⁶,3s² ,3p³

3.Without referring the periodic table ,write the electron configuration of elements with following atomic number:

a)      9

b)      20

c)       26

d)      33

Classify the element in group ,period and block

4.Specify the group of the periodic table in which each of the following elements is fund:

a)      [Ne],3s¹ ,

b)      [Ne],3s² ,3p⁶

c)       [Ne],3s² ,3p³

d)      [Ar],3s² ,3d⁸

5.Write the ground state electron configuration following ions:

        a) Li⁺      b) H^-       c) F-       d) Sn²⁺                  e) Al³⁺                   f)S^2-        g)Ba²⁺                    h)Rb⁺

6. Which the largest atom  in second period ?

7. Which is the largest atom in  I-A

8. Consider  the second period of periodic table as an example to show that size of atom decrease as we move left to right . Explain the trend.

9. List the following ion in order of increase ionic radius : N³-,Na⁺,F^-,Mg²⁺,O^2-

10. Indicate which one of the species in each of the  following pair is similer:

        a) Cl or Cl^-            b) Na or Na⁺       c) O^2- or S^2-          d) Mg²⁺ or Al ³⁺                  d)Au²⁺ or  Au³⁺

11. Why ionization energy and electro affinity  measurements are usually made when  atoms are in the gaseous state .

12. Why the second ionization energy is always greater than the first ionization energy for any element ?

13. What type of elements have the highest ionization energies  and what type of element have the lowest ionization energies?

14. Explain why alkali metals have a greater electron affinity for electrons than alkaline earth metals.   

15. Explain why the first electron affinity of sulphur is 200 kJ/mol but the second electron affinity is    -649 kJ/mol.