Based on the information in the table, which elements are most likely in the same periods of the periodic table? Facts about Five Elements Element Atomic mass amu Total electrons Valence electrons Year isolated Aluminum Al 27 13 3 1825 Boron cap b 11 5 3 1808 Carbon cap c 12 6 4 1803 Gallium Ga 70 31 3 1875 Germanium Ge 73 32 4 1886
Answer
A
Boron and carbon are likely together in one period because they have very close atomic masses, while gallium and germanium are likely together in another period because they have very close atomic masses.
B
Aluminum, boron, and carbon are likely together in one period because they were first isolated in the first half of the 1800s, while gallium and germanium are likely together in another period because they were first isolated in the second half.
C
Boron and carbon are likely together in one period because they each end in “-on,” while aluminum, gallium, and germanium are likely together in another period because they each end in “-ium.”
D
Aluminum, boron, and gallium are likely together in one group because they have the same number of valence electrons, and carbon and germanium are likely together in another group because they have the same number of valence electrons.
Explanation
Boron has 5 electrons and carbon has 6; their electrons occupy two shells, so both are in period 2. Gallium has 31 electrons and germanium has 32; both have electrons in four shells, so both are in period 4. Their close atomic masses happen to match these pairs, but electron shells—not atomic mass—identify a period.
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