Answer:
The elements are arranged in seven horizontal rows, called periods or series, and 18 vertical columns, called groups.
Explanation:
In chemistry, a group (also known as a family) is a column of elements in the periodic table of the chemical elements. ... Groups may also be identified using their topmost element, or have a specific name. For example, group 16 is also described as the "oxygen group" and as the "chalcogens".
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