Question

Complete the second pair.
Horizontal row: Periods : : _____________ : Groups

Answer 1

The periodic table is defined as the arrangement of the elements which are known in accordance to their increasing atomic number and their recurring chemical properties. The periodic table is been sorted in the form of a tabular arrangement where a row is considered to be a period and the column is a group. The modern periodic table which we use now is the new and the improved version of the models which were put forth by the scientists in the 19 th and the 20 th century.

Complete step-by-step answer: In the modern periodic table the elements are arranged from left to right as well as from top to bottom in accordance with their increasing atomic number. The horizontal rows which are present in the periodic table are known as periods. There are seven periods in the modern periodic table. The elements which are present in the same period will have an increasing order of the valence electrons. So this will increase the energy level of the atom so the energy sublevels per energy level will also increase.
While in the modern periodic table there are 18 vertical columns which are known as groups. So there are 18 groups in the periodic table. The elements which are present in the same group will contain a number of the valence electron configuration so they will have similar chemical properties.
So the answer is vertical columns: Horizontal row: Periods : : Vertical columns : Groups.

Note: There are 118 elements present in the modern periodic table. The first ninety four (94) elements present in the periodic table occur naturally. Whereas the rest elements from 95 to 118 are synthesised in laboratories or nuclear reactors. The father of the periodic table is considered to be Dimitri Mendeleev who first put forth the first iteration of the periodic table similar to the one which is used now.