21. Write ground-state electron configurations for the following elements.
a. bromine (Br)
b. strontium (Sr)
c. antimony (Sb)
d. rhenium (Re)
e. terbium (Tb)
f. titanium (Ti)
22. A chlorine atom in its ground state has a total of seven electrons in orbitals related to the atom’s third
energy level. How many of the seven electrons occupy p orbitals? How many of the 17 electrons in a
chlorine atom occupy p orbitals?
23. When a sulfur atom reacts with other atoms, electrons in orbitals related to the atom’s third energy
level are involved. How many such electrons does a sulfur atom have?
24. An element has the ground-state electron configuration [Kr]5s24d105p1. It is part of some
semiconductors and used in various alloys. What element is it?
25. Challenge In its ground state, an atom of an element has a total of two electrons in all orbitals
related to the atom’s highest energy level for which
n  6. Using noble-gas notation, write the electron configuration for this element, and identify the
element.
26. Draw electron-dot structures for atoms of the following elements.
a. magnesium
b. thallium
c. xenon
27. An atom of an element has a total of 13 electrons. What is the element, and how many electrons are
shown in its electron-dot structure?
28. Challenge This element exists in the solid state at room temperature and at normal atmospheric
pressure and is found in emerald gemstones. It is known to be one of the following elements: carbon,
germanium, sulfur, cesium, beryllium, or argon. Identify the element based on the electron-dot
structure below.
33. Interpreting Scientific Illustrations Which is the correct electron-dot structure for an atom of
selenium? Explain.
66. How many energy sublevels are contained in each of the hydrogen atom’s first three energy levels?
70. What is the maximum number of electrons an orbital may contain?
72. How many electrons can be contained in all the orbitals related to an argon atom’s third energy
level?
76. In what sequence do electrons fill the atomic orbitals related to a sublevel?
78. What are valence electrons? How many of a magnesium atom’s 12 electrons are valence electrons?
81. How many electrons are shown in the electron-dot structures of the following elements?
a. carbon
b. iodine
c. calcium
d. gallium
82. When writing the electron configuration notation for an atom, what three principles or rules do you
follow?
83. Write the electron configuration and draw the orbital notation for atoms of oxygen and sulfur.
86. Use noble-gas notation to describe the electron configurations of the elements represented by the
following symbols.
a. Kr
b. P
c. Zr
d. Pb
87. What elements are represented by each of the following electron configurations?
a. 1s22s22p5
b. [Ar]4s2
c. [Xe]6s24f4
d. [Kr]5s24d105p4
e. [Rn]7s25f13
f. 1s22s22p63s23p64s23d104p5
90. Draw electron-dot structures for atoms of each of the following elements.
92. Which element could have the ground-state electron-dot notation shown in Figure 26?
a. manganese
b. antimony
c. calcium
d. samarium
93. For an atom of tin in the ground state, write the electron configuration using noble-gas notation and
draw the electron-dot structure.
94. What is the maximum number of electrons that can be contained in an atom’s orbitals having the
following principal quantum numbers?
a. 3
b. 4
c. 6
d. 7
98. Which elements have only two electrons in their electron-dot structures: hydrogen, helium, lithium,
aluminum, calcium, cobalt, bromine, krypton, and barium?
____________________________________________________________________________
8.Without using the periodic table, determine the group, period, and block of an atom with the following
electron configurations.
a. [Ne]3s2
b. [He]2s2
c. [Kr]5s24d105p5
Electron
Configuration
Group
Period
Block
a. [Ne]3s2
b. [He]2s2
c. [Kr]5s24d105p5
9. What are the symbols for the elements with the following valence electron configurations?
a. s2d1
b. s2p3
c. s2p6
10. Challenge Write the electron configuration of the following elements.
a. the group 2 element in the fourth period
b. the group 12 element in the fourth period
c. the noble gas in the fifth period
d. the group 16 element in the second period
11. Explain what determines the blocks in the periodic table.
12. Determine in which block of the periodic table are the elements having the following valence
electron configurations.
a. s2p4
b. s1
c. s2d1
d. s2p1
13. Infer Xenon, a nonreactive gas used in strobe lights, is a poor conductor of heat and electricity.
Would you expect xenon to be a metal, a nonmetal, or a metalloid? Where would you expect it to be
on the periodic table? Explain.
14. Explain why elements within a group have similar chemical properties.
15. Model Make a simplified sketch of the periodic table and label the s-, p-, d-, and f-blocks.
48. Determine the group, period, and block in which each of the following elements is located in the
periodic table.
a. [Kr]5s24d1
b. [Ar]4s23d104p3
c. [He]2s22p6
d. [Ne]3s23p1
57. Identify each missing part of Table 6.8.
Period
Group
3
4
Element
Electron
Configuration
Mg
[Ne]3s2
14
Ge
12
Cd
[Kr]5s24d10
2
[He]2s1
1
a. 2
c. 5
2
10
2
b. [Ar]4s 3d 4p
d. Li
77. Figure 22 shows different sections of the periodic table. Give the name of each section, and explain
what the elements in each section have in common.