Name: Variation of Atomic Radius in Periodic Table
Uploaded: 2019-07-19
Duration: 4 min 6 s
Description: The atomic radius is defined as the distance between the atom's nucleus and the outermost shell. But do you know how it varies in the periodic table? Let's find the answer in this video.

Question

Discuss the important characteristics of periods and groups with reference to the Modern Periodic Table.

Accepted Answer

Important characteristics of periods –

1. The horizontal rows in the periodic table are known as periods. They have same number of shells. There are 7 periods in modern periodic table. The first period contains only 2 elements and is the shortest period.

2. The second and third period contain 8 elements and are called short periods.

3. The fourth and fifth period contains 18 elements. these are long periods.

4. The sixth period contain 32 elements. It is longest period.

5. The seventh period is incomplete.

6. Lanthanoids and Actinoids are placed in 6^th and 7^th period respectively.

Important characteristics of groups –

1. A group may be defined as vertical column in the periodic table. In terms of electronic structure of the atom, a group constitutes a series of elements whose atoms have the same outermost electronic configurations. Each group contains elements that tend to react chemically in similar ways, because they all have atoms in which the arrangement of electrons around the nucleus is similar.

2. Some groups in the periodic table are given special names e.g.

Group 1 — the alkali metals

Group 2 — the alkaline earth metals

Group 16 — the chalcogens

Group 17 — the halogens

Group 18 — the noble gases

Discuss the important characteristics of periods and groups with reference to the Modern Periodic Table.

Important Questions on Periodic Classification of Elements

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