Question

Five elements A, B, C, D and E have atomic number 1,2,5,6 and 8 respectively. Answer the following questions.
(i) Which element forms positive ions?
(ii) Which elements has five electrons in the valence shell?
(iii) Which element has highest electron affinity?
(iv) Which element has highest ionization potential?

Answer 1

Part 1: Positive ion:-

1. A positive ion or a positively charged ion is a cation that has less number of electrons than protons.
2. Element A which is Hydrogen will form a positive ion.
3. Element C which is Boron will form a positive ion.

Part 2: Five electrons in valence shell:-

1. None of the above-mentioned elements has five electrons in its valence shell.
2. A has 1 electron. $1$
3. B has 2 electrons. $2$
4. C has 3 electrons. $2,3$
5. D has 4 electrons $2,4$
6. E has 6 electrons. $2,6$

Part 3: Highest electron affinity:-

1. It is the amount of energy released when an electron is added to a neutral atom in order to form an anion.
2. Element E which is Oxygen has the highest electron affinity.
3. This is because it only needs 2 electrons to have completely filled outermost shell and be stable.

Part 4: Highest ionization potential:-

1. Ionization enthalpy or ionization energy is the amount of energy required for the removal of an electron from an isolated gaseous atom.
2. Ionization enthalpy increases across a period from left to right and decreases as we go down the group.
3. Element B which is Helium has the highest ionization enthalpy.
4. Since it is a noble gas, it has 2 electrons in its valence shell and is in a duplet state and we know that noble gases have the highest ionization energies.

Final answer:-

(i) Elements A and C will form positive ions

(ii) None of the elements mentioned have 5 electrons in its valence shell.

(iii) Element E has the highest electron affinity.

(iv) Element B has the highest ionization potential.