Page 77 - Theory and Problems of BEGINNING CHEMISTRY

66 ELECTRONIC CONFIGURATION OF THE ATOM [CHAP. 4

4.34. Write the electronic configurations of K and Cu. What differences are there that could explain why K is so active
and Cu so relatively inactive?
6
6
2
2
2
Ans. K 1s 2s 2p 3s 3p 4s 1
2
1
6
2
6
2
Cu 1s 2s 2p 3s 3p 4s 3d 10
The differences are the additional 10 protons in the nucleus and the additional ten 3d electrons that go along
with them. Adding the protons and adding the electrons in an inner subshell make the outermost electron
more tightly bound to the nucleus.
4.35. Starting at the first electron added to an atom, (a) what is the number of the first electron in the second shell of
the atom? (b) What is the atomic number of the first element of the second period? (c) What is the number of the
first electron in the third shell of the atom? (d ) What is the atomic number of the first element of the third period?
(e) What is the number of the first electron in the fourth shell of that atom? ( f ) What is the atomic number of the
first element of the fourth period?
Ans. (a) and (b)3 (c) and (d )11 (e) and (f )19
There obviously is some relationship between the electronic configuration and the periodic table.
4.36. Check Table 4-3 to ensure that no two electrons have the same set of four quantum numbers.
4.37. Write the electronic configuration of atoms of each of the following elements, using the periodic table as a memory
aid: (a)P,(b) Cl, (c) Mn, and ( d ) Zn.
2
2
2
6
2
6
2
2
2
6
Ans. (a)1s 2s 2p 3s 3p 3 (c) 1s 2s 2p 3s 3p 4s 3d 5
2
2
6
2
6
2
2
6
2
2
(b)1s 2s 2p 3s 3p 5 (d)1s 2s 2p 3s 3p 4s 3d 10
4.38. Write the outer electronic configuration of atoms of each of the following elements, using the periodic table as a
memory aid: (The atomic numbers are indicated for your convenience.) (a) 57 La, (b) 92 U, (c) 88 Ra, and (d ) 82 Pb.
2
Ans. (a) La [Xe] 6s 5d 1 (c) Ra [Rn] 7s 2
2
14
2
10
1
(b) U [Rn] 7s 6d 5 f 3 (d) Pb [Xe] 6s 5d 4f 6p 2
4.39. Write the expected outer electronic configuration of atoms of each of the following elements, using the periodic
table as a memory aid: (The atomic numbers are indicated for your convenience.) (a) 64 Gd, (b) 90 Th, (c) 55 Cs, and
(d ) 71 Lu.
2
1
Ans. (a) Gd [Xe] 6s 5d 4f 7 (c) Cs [Xe] 6s 1
1
1
2
2
(b) Th [Rn] 7s 6d 5f 1 (d) Lu [Xe] 6s 5d 4f 14