Chapter 7, Problem 58A

Solution

(a)

Interpretation:

The reactivity of potassium needs to be explained based on electron configuration.

Concept introduction:

The electronic configuration is method of arranging the electrons in the energy shells depending on the number of atomic numbers. The atomic number is number of protons and number of neutrons. Each neutral atom will have equal number of protons and neutrons. The electrons are filled in the energy shells that follow Aufbau’s principle. The outermost electrons will define the property of the element.

Potassium is very reactive as the outermost one electron can be easily removed due to the shielding effect of other energy shells.

Potassium belongs to Group 1 in the periodic table. It has atomic number as 19. The electronic configuration is ${\text{1s}}^2{\text{2s}}^2{\text{2p}}^6{\text{3s}}^2{\text{3p}}^6{\text{4s}}^1$.

It has one valence electrons in its outermost shell. But this outermost electron is shielded from the attractive forces of the nucleus due to the presence of other energy shells. As a result of this, this outermost electron is easily removed and hence Potassium is very reactive.

(b)

Interpretation:

The reactivity of fluorine based on electron configuration needs to be explained.

Concept introduction:

The electronic configuration is method of arranging the electrons in the energy shells depending on the number of atomic numbers. The atomic number is number of protons and number of neutrons. Each neutral atom will have equal number of protons and neutrons. The electrons are filled in the energy shells that follows Aufbau’s principle. The outermost electrons will define the property of the element.

Fluorine is very reactive as the outermost shells are closer to the nucleus with high electro negativity.

Fluorine belongs to Group 17 in the periodic table. It has atomic number as 9. The electronic configuration is ${\text{1s}}^2{\text{2s}}^2{\text{2p}}^5$.

It has five valence electrons in its outermost shell. It needs one more electron to become an octet. It will absorb one electron from any electron donor to form an ionic compound. Moreover, the electrons in outer shells are closer to the nucleus resulting in stronger forces of attraction. Hence, its electro negativity is high. Hence, Fluorine is highly reactive.

(c)

Interpretation:

The reactivity of neon based on electron configuration needs to be explained.

Concept introduction:

The electronic configuration is method of arranging the electrons in the energy shells depending on the number of atomic numbers. The atomic number is number of protons and number of neutrons. Each neutral atom will have equal number of protons and neutrons. The electrons are filled in the energy shells that follows Aufbau’s principle. The outermost electrons will define the property of the element.

Neon is not reactive as all its shells are completely filled and does not need electrons.

Neon belongs to Group 18 in the periodic table. It has atomic number as 10. The electronic configuration is ${\text{1s}}^2{\text{2s}}^2{\text{2p}}^6$.

It can be noticed that all the shells of this element are completely filled and does not require any electron to stabilize it. As a result of this, Neon is not reactive.