Question

Answer the following questions regarding the modern version of Mendeleev's periodic table.

How many elements are in first period? Name the elements.

Answer 1

The first period contains only one element.

• This element is Hydrogen $\left(\mathrm{H}\right)$.

Periods: The horizontal rows in the Mendeleev's periodic table are known as periods.

• Mendeleev originally called these periods as series.
• The number of periods present in modern version of Mendeleev's periodic table is 7.
• In Mendeleev's periodic table, elements were arranged in the order of the increasing atomic weights.
• The elements were arranged in the form of vertical columns called groups and horizontal rows called periods.