Question

Reference to the long form of the periodic table fill in the blanks with appropriate words:

The fourth and fifth periods have_____elements and are called_____periods.

• A. 18
• B. Long

Answer 1

Modern periodic table:

• The modern periodic table is an arrangement of all the elements known in accordance with their increasing atomic number and recurring chemical properties.
• It is a tabular display of 118 chemical elements which consists of horizontal rows called periods and vertical columns are called groups.
• All elements in a period have the same number of electron shells.
• The fourth period contains 18 elements starting with Potassium and ending with krypton.
• The fourth and fifth periods are called long periods as they contain 18 elements.

So, The fourth and fifth periods have 18 elements and are called Long periods.