Periods (periodic table)

row in the periodic table: repetition of properties in chemical elements when ordered by atomic number:

first row (or period) of the periodic table of the chemical elements

any of the chemical elements in the second row of the periodic table

third row of the periodic table

fourth row in the periodic table of chemical elements

row 6 of the periodic table

fifth row of the periodic table

any element in row 7 of the periodic table

period 8 (row 8) of the periodic table. (Today, theoretically only)

period 9 (row 9) of the periodic table (today, theoretical only)

row 10 of the periodic table (today, theoretical only)