Question

What do all elements in a horizontal column of periodic table have in common?

Answer 1

Hint : The vertical columns on the periodic table are called groups or families because of their similar chemical behavior. The horizontal rows on the periodic table are called periods. All the members of a family of elements have the same number of valence electrons and similar chemical properties.

Complete Step By Step Answer:
The horizontal rows on the periodic table are called periods. All the members of a family of element have the same number of valence electrons and similar chemical properties. In the same period, electrons fill the same valence shell.
To go somewhat further, the first shell can oblige $2$ electrons to form the primary electronic shell, and hence a Period of the Table has been portrayed; the second valence shell can oblige up to $8$ electrons and so on.
This electronic structure directs why, and the manner in which we compose the Periodic Table. Full valence shells, for example the element has $2$ or $10$ electrons, are steady electronic structures.
The ground state configurations play a major role in determining how an element reacts and what compounds it forms. The structure of the table also predicts how the properties vary. For instance, atomic radius increases down a group as do metallic character.

Note :
Mendeleev’s Periodic Table was built by listing the known elements in order of increasing atomic mass and grouping the elements by their properties. He also left blanks in the table. In modern times, we know that the elements in a given group have the same number of valence electrons, with ground state configurations having a consistent pattern.