Question

The long form of the periodic table consists of ______ horizontal rows and _______ vertical columns.

Answer 1

Hint: - The periodic table is a tabular display of the chemical elements which are arranged by atomic number, electron configuration, and recurring chemical properties.

Complete answer:
Modern or long form of the periodic table is based on the modern periodic law. The table is the arrangement of elements in increasing order of their atomic numbers. It consists of 18 vertical columns and 7 horizontal rows.
Vertical columns are known as Groups in the Periodic Table
1. There are 18 groups in the periodic table.
2. They are numbered from 1 to 18.
3. Each group consists of elements having the same outer shell electronic configuration.

Horizontal rows are known as Periods in the Periodic Table
1. There are 7 periods in the periodic table.
2. They are numbered as 1, 2, 3, 4, 5, 6 and 7 from top to bottom.
3. The 1st period consists of only two elements i.e. hydrogen and helium.
4. 2nd and 3rd period consist of 8 elements each, 4th and 5th period consist of 18 elements each, 6th period consists of 32 elements, 7th period of the periodic table four new elements.
5. Also, the long form of the periodic table consists of a separate panel at the bottom. It consists of 14 elements of the 6th period 14 elements in the 7th period.
6. Each period represents the number of shells or energy levels present in an atom of an element.
The cause of periodicity in properties is the repetition of similar outer electronic configuration after certain regular intervals.

Therefore, the correct answer is 7 horizontal rows and 18 vertical columns.

Note: - The modern periodic law states that the physical and chemical properties of the elements are the periodic functions of their atomic number therefore elements are arranged in increasing order of their atomic numbers from left to right across each row.