The Modern Periodic Table

The modern periodic table is a tabular arrangement of all the chemical elements, organized on the basis of their atomic structure and chemical properties. It is divided into seven horizontal rows called periods and 18 vertical columns called groups.

Periods

Each period in the periodic table corresponds to a new energy level in the electron configuration of the elements. The first period has only two elements, hydrogen and helium, which have one and two electrons respectively. The second period has eight elements, from lithium to neon, which have two energy levels and two to eight electrons. Each subsequent period has more elements, with increasing numbers of energy levels and electrons.

Groups

The vertical columns in the periodic table are called groups or families. The elements in each group have similar properties due to their similar electron configurations. There are 18 groups in the modern periodic table, numbered from 1 to 18. The elements in each group have similar valence electron configurations and therefore similar chemical properties.

Numbering of Groups

The groups in the periodic table are numbered from 1 to 18. The first two groups are the alkali metals and the alkaline earth metals, respectively. The next ten groups are numbered from 3 to 12 and are known as the transition elements. The last six groups are numbered from 13 to 18 and are known as the p-block elements.

Conclusion

Thus, the correct answer to the question is option 'D' which states that the modern periodic table is divided into 7 periods and 18 groups.

Elements are arranged on the basis of increasing order of atomic numbers.

The horizontal rows in the periodic table are called Periods and the vertical columns are known as the Groups.

The elements in the Modern Periodic Table are arranged in 7 Periods and 18 Groups.

The elements in the Modern Periodic Table are classified into four categories viz. Representative Elements, Transition Elements, Inner Transition Elements, and Noble Gases.