객관식
Which element is the most abundant in the Earth's crust by mass?
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4. Atoms and Elements
Periodic Table: Classifications
Multiple Choice
How many periods (horizontal rows) are in the modern periodic table?
A
18
B
8
C
118
D
7
검증된 단계별 안내1
Understand that the periodic table is organized into horizontal rows called periods and vertical columns called groups or families.
Recall that each period corresponds to the filling of a different electron shell or energy level in atoms.
Recognize that the modern periodic table consists of elements arranged in 7 periods, representing 7 electron shells being filled.
Note that the number 18 refers to the number of groups (vertical columns), not periods.
Therefore, the number of periods (horizontal rows) in the modern periodic table is 7.
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