Answer:
B: 18
Step-by-step explanation:
A group is a vertical column of the periodic table based on the organization of the outer shell electrons. There are a total of 18 groups. From left to right in the periodic table, there are two groups (1 and 2) of elements in the hydrogen block, ten groups (3 through 12) in the transition block, and six groups (13 through 18) in the main block. The elements in the inner-transition block (lanthanoids and actinoids) are not given group numbers.
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