
Concept explainers
(a)
Interpretation:
The number of electrons present in the outer shell of Si should be identified.
Concept Introduction:
The protons and neutrons of an atom are present in the nucleus of an atom whereas the electrons are always moving around the nucleus of an atom that is they possess kinetic energy. The lowest possible energy level of an electron in an atom is its ground state.
The electrons are arranged around the nucleus of an atom in an increasing order of energy levels and this description of orbitals of atom occupied by electrons is known as electronic configuration.

Answer to Problem 2.84P
The number of electrons in outermost shell of Si is 4.
Explanation of Solution
Electrons are distributed in the orbitals of the subshell. The specific region of space in which the movement of electrons is confined is said to be shells which are divided into subshells and are s-, p-, d-, and f-. Among these subshells, the electrons are grouped as orbitals.
The number of electrons that these subshells can hold is:
s-block - 2.
p-block - 6.
d-block - 10.
f-block - 14.
The electronic configuration of Si (14) is 1s2 2s2 2p6 3s2 3p2.
On the basis of above electronic configuration, the outermost shell or valence shell is 3s 3p which contains four electrons.
Thus, number of electrons in outermost shell of Si is 4.
(b)
Interpretation:
The number of electrons present in the outer shell of Br should be identified.
Concept Introduction:
The protons and neutrons of an atom are present in the nucleus of an atom whereas the electrons are always moving around the nucleus of an atom that is they possess kinetic energy. The lowest possible energy level of an electron in an atom is its ground state.
The electrons are arranged around the nucleus of an atom in an increasing order of energy levels and this description of orbitals of atom occupied by electrons is known as electronic configuration.

Answer to Problem 2.84P
The number of electrons in outermost shell of Br is 7.
Explanation of Solution
Electrons are distributed in the orbitals of the subshell. The specific region of space in which the movement of electrons is confined is said to be shells which are divided into subshells and are s-, p-, d-, and f-. Among these subshells, the electrons are grouped as orbitals.
The number of electrons that these subshells can hold is:
s-block - 2.
p-block - 6.
d-block - 10.
f-block - 14.
The electronic configuration of Br (35) is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p5.
On the basis of above electronic configuration, the outermost shell or valence shell is 4s 4p which contains seven electrons.
Thus, number of electrons in outermost shell of Br is 7.
(c)
Interpretation:
The number of electrons present in the outer shell of p should be identified.
Concept Introduction:
The protons and neutrons of an atom are present in the nucleus of an atom whereas the electrons are always moving around the nucleus of an atom that is they possess kinetic energy. The lowest possible energy level of an electron in an atom is its ground state.
The electrons are arranged around the nucleus of an atom in an increasing order of energy levels and this description of orbitals of atom occupied by electrons is known as electronic configuration.

Answer to Problem 2.84P
The number of electrons in outermost shell of p is 5.
Explanation of Solution
Electrons are distributed in the orbitals of the subshell. The specific region of space in which the movement of electrons is confined is said to be shells which are divided into subshells and are s-, p-, d-, and f-. Among these subshells, the electrons are grouped as orbitals.
The number of electrons that these subshells can hold is:
s-block - 2.
p-block - 6.
d-block - 10.
f-block - 14.
The electronic configuration of p (15) is 1s2 2s2 2p6 3s2 3p3.
On the basis of above electronic configuration, the outermost shell or valence shell is 3s 3p which contains five electrons.
Thus, number of electrons in outermost shell of p is 5.
(d)
Interpretation:
The number of electrons present in the outer shell of K should be identified.
Concept Introduction:
The protons and neutrons of an atom are present in the nucleus of an atom whereas the electrons are always moving around the nucleus of an atom that is they possess kinetic energy. The lowest possible energy level of an electron in an atom is its ground state.
The electrons are arranged around the nucleus of an atom in an increasing order of energy levels and this description of orbitals of atom occupied by electrons is known as electronic configuration.

Answer to Problem 2.84P
The number of electrons in outermost shell of K is 1.
Explanation of Solution
Electrons are distributed in the orbitals of the subshell. The specific region of space in which the movement of electrons is confined is said to be shells which are divided into subshells and are s-, p-, d-, and f-. Among these subshells, the electrons are grouped as orbitals.
The number of electrons that these subshells can hold is:
s-block - 2.
p-block - 6.
d-block - 10.
f-block - 14.
The electronic configuration of K (19) is 1s2 2s2 2p6 3s2 3p6 4s1.
On the basis of above electronic configuration, the outermost shell or valence shell is 4s which contains one electron.
Thus, number of electrons in outermost shell of K is 1.
(e)
Interpretation:
The number of electrons present in the outer shell of He should be identified.
Concept Introduction:
The protons and neutrons of an atom are present in the nucleus of an atom whereas the electrons are always moving around the nucleus of an atom that is they possess kinetic energy. The lowest possible energy level of an electron in an atom is its ground state.
The electrons are arranged around the nucleus of an atom in an increasing order of energy levels and this description of orbitals of atom occupied by electrons is known as electronic configuration.

Answer to Problem 2.84P
The number of electrons in outermost shell of He is 2.
Explanation of Solution
Electrons are distributed in the orbitals of the subshell. The specific region of space in which the movement of electrons is confined is said to be shells which are divided into subshells and are s-, p-, d-, and f-. Among these subshells, the electrons are grouped as orbitals.
The number of electrons that these subshells can hold is:
s-block - 2.
p-block - 6.
d-block - 10.
f-block - 14.
The electronic configuration of He (2) is 1s2.
On the basis of above electronic configuration, the outermost shell or valence shell is 1s which contains two electrons.
Thus, number of electrons in outermost shell of He is 2.
(f)
Interpretation:
The number of electrons present in the outer shell of Ca should be identified.
Concept Introduction:
The protons and neutrons of an atom are present in the nucleus of an atom whereas the electrons are always moving around the nucleus of an atom that is they possess kinetic energy. The lowest possible energy level of an electron in an atom is its ground state.
The electrons are arranged around the nucleus of an atom in an increasing order of energy levels and this description of orbitals of atom occupied by electrons is known as electronic configuration.

Answer to Problem 2.84P
The number of electrons in outermost shell of Ca is 2.
Explanation of Solution
Electrons are distributed in the orbitals of the subshell. The specific region of space in which the movement of electrons is confined is said to be shells which are divided into subshells and are s-, p-, d-, and f-. Among these subshells, the electrons are grouped as orbitals.
The number of electrons that these subshells can hold is:
s-block - 2.
p-block - 6.
d-block - 10.
f-block - 14.
The electronic configuration of Ca (20) is 1s2 2s2 2p6 3s2 3p6 4s2.
On the basis of above electronic configuration, the outermost shell or valence shell is 4s which contains two electrons.
Thus, number of electrons in outermost shell of Ca is 2.
(g)
Interpretation:
The number of electrons present in the outer shell of Kr should be identified.
Concept Introduction:
The protons and neutrons of an atom are present in the nucleus of an atom whereas the electrons are always moving around the nucleus of an atom that is they possess kinetic energy. The lowest possible energy level of an electron in an atom is its ground state.
The electrons are arranged around the nucleus of an atom in an increasing order of energy levels and this description of orbitals of atom occupied by electrons is known as electronic configuration.

Answer to Problem 2.84P
The number of electrons in outermost shell of Kr is 8.
Explanation of Solution
Electrons are distributed in the orbitals of the subshell. The specific region of space in which the movement of electrons is confined is said to be shells which are divided into subshells and are s-, p-, d-, and f-. Among these subshells, the electrons are grouped as orbitals.
The number of electrons that these subshells can hold is:
s-block - 2.
p-block - 6.
d-block - 10.
f-block - 14.
The electronic configuration of Kr (36) is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6.
On the basis of above electronic configuration, the outermost shell or valence shell is 4s 4p which contains eight electrons.
Thus, number of electrons in outermost shell of Kr is 8.
(h)
Interpretation:
The number of electrons present in the outer shell of Pb should be identified.
Concept Introduction:
The protons and neutrons of an atom are present in the nucleus of an atom whereas the electrons are always moving around the nucleus of an atom that is they possess kinetic energy. The lowest possible energy level of an electron in an atom is its ground state.
The electrons are arranged around the nucleus of an atom in an increasing order of energy levels and this description of orbitals of atom occupied by electrons is known as electronic configuration.

Answer to Problem 2.84P
The number of electrons in outermost shell of Pb is 4.
Explanation of Solution
Electrons are distributed in the orbitals of the subshell. The specific region of space in which the movement of electrons is confined is said to be shells which are divided into subshells and are s-, p-, d-, and f-. Among these subshells, the electrons are grouped as orbitals.
The number of electrons that these subshells can hold is:
s-block - 2.
p-block - 6.
d-block - 10.
f-block - 14.
The electronic configuration of Pb (82) is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 4f14 5d10 6s2 6p2.
On the basis of above electronic configuration, the outermost shell or valence shell is 6s 6p which contains four electrons.
Thus, number of electrons in outermost shell of Pb is 4.
(i)
Interpretation:
The number of electrons present in the outer shell of Se should be identified.
Concept Introduction:
The protons and neutrons of an atom are present in the nucleus of an atom whereas the electrons are always moving around the nucleus of an atom that is they possess kinetic energy. The lowest possible energy level of an electron in an atom is its ground state.
The electrons are arranged around the nucleus of an atom in an increasing order of energy levels and this description of orbitals of atom occupied by electrons is known as electronic configuration.

Answer to Problem 2.84P
The number of electrons in outermost shell of Se is 6.
Explanation of Solution
Electrons are distributed in the orbitals of the subshell. The specific region of space in which the movement of electrons is confined is said to be shells which are divided into subshells and are s-, p-, d-, and f-. Among these subshells, the electrons are grouped as orbitals.
The number of electrons that these subshells can hold is:
s-block - 2.
p-block - 6.
d-block - 10.
f-block - 14.
The electronic configuration of Se (34) is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p4.
On the basis of above electronic configuration, the outermost shell or valence shell is 4s 4p which contains six electrons.
Thus, number of electrons in outermost shell of Se is 6.
(j)
Interpretation:
The number of electrons present in the outer shell of O should be identified.
Concept Introduction:
The protons and neutrons of an atom are present in the nucleus of an atom whereas the electrons are always moving around the nucleus of an atom that is they possess kinetic energy. The lowest possible energy level of an electron in an atom is its ground state.
The electrons are arranged around the nucleus of an atom in an increasing order of energy levels and this description of orbitals of atom occupied by electrons is known as electronic configuration.

Answer to Problem 2.84P
The number of electrons in outermost shell of O is 6.
Explanation of Solution
Electrons are distributed in the orbitals of the subshell. The specific region of space in which the movement of electrons is confined is said to be shells which are divided into subshells and are s-, p-, d-, and f-. Among these subshells, the electrons are grouped as orbitals.
The number of electrons that these subshells can hold is:
s-block - 2.
p-block - 6.
d-block - 10.
f-block - 14.
The electronic configuration of O (8) is 1s2 2s2 2p4.
On the basis of above electronic configuration, the outermost shell or valence shell is 2s 2p which contains six electrons.
Thus, number of electrons in outermost shell of O is 6.
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Chapter 2 Solutions
Introduction to General, Organic and Biochemistry
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