Science Fill in the blank

Group 17 elements are known as Halogens.

On moving from left to right in a period in the periodic table, the size of the atom Decreases.
Explanation:
Atomic size decreases from left to right in the Periodic Table.

The horizontal rows in a periodic table are called Periods​​​​​​​.

Group 18 elements are called Noble Gases.

The tendency to gain an electron Decreases on moving down in a group of the periodic table.

A periodic table consists of horizontal rows of elements called vertical columns of elements and vertical columns called.
Explanation:
All the members of a family of elements have the same number of valence electrons and similar chemical properties. The horizontal rows on the periodic table are called periods.

In going across a period (right to left) in periodic table, the atomic size of the atom Increases.

According to Newlands’ classification of elements, the properties of sulphur are similar to those of oxygen because sulphur is the Eighth element starting from oxygen.

On going down in a group in the periodic table, the metallic character of elements Increases.

On moving from right to leftin the second period, the number of valence electrons Decreases.

Group 1 elements are called Alkali metals.
Explanation:
These metals are called alkali metals because they form alkalies.

Group 1 elements are called Alkali metals.

The number of valence electrons 8 to 1 along a period from left to right.
Explanation:
On moving from left to right in a period, the number of valence electrons decreases from 8 to 1. As a result, valency across a period first increases and then decreases. Valency increases from +1, +2, +3 till +4 in a period and then decreases -4, -3, -2, -1.

The horizontal rows in a periodic table are called Periods.