Lanthanides
The first period is at the top of the table. It consists of hydrogen and helium. The bottom period is period 7.
The horizontal rows on the Periodic Table are called periods, while the vertical columns are called groups or families. For instance, iodine is in the same group, but different period to fluorine, chlorine and bromine.
The horizontal rows of the periodic table are called Periods and the vertical rows are called groups.
the horizontal lines are called periods and the vertical lines are called groups.
Each (horizontal) row is called a '''period''', whereas each (vertical) column is called a group.
lanthanides
The first period is at the top of the table. It consists of hydrogen and helium. The bottom period is period 7.
Actinides
The first three periods of the periodic table are called the first period, second period, and third period.
The properties which change regulary from top to bottom in a group and from leaft to right a period are called periodic property.
The first period of human life is called pre-history
Confuse question; probable you think to lanthanides.
Hydrogen
The first month of life is called the neonatal period.
Orphan
On the left side (the first 12 columns + the bottom four in the 13th column+the bottom two in the 14th column+the bottom one in the 15th column)
The second period at the bottom of the table is called the lanthanide series or the lanthanoid series. It consists of 14 elements with atomic numbers 57 to 70 and is located below the main body of the periodic table.