columns in the periodic table are reffered to as "periods". periods represent elements with the same number of shells i.e all elements in period 1 have 1 shell (k shell) and vice versa.
The vertical columns of the periodic table are called groups, or families. The significance is elements with similar properties are placed in the same vertical columns. The horizontal rows of the periodic table are called periods. The significance is that properties vary from left to right along the rows.
