Question

horizontal row is period, group or zero group

Answer 1

I have my own written answer here it is
period

Answer 2

A period is a horizontal row of theperiodic table. There are seven periodsin the periodic table, with each one beginning at the far left. A new periodbegins when a new principal energy level begins filling with electrons.Period 1 has only two elements (hydrogen and helium), while periods 2 and 3 have 8 elements.