### Theory:

Features of the Groups:
The vertical columns in the periodic table start from top to bottom, are called groups. The periodic table has $$18$$ groups.
Based on the common properties of the elements, they are classified into different families.

 Group Number Family $$1$$ Alkali Metals $$2$$ Alkaline earth metals $$3$$ to $$12$$ Transition metals $$13$$ Boron Family $$14$$ Carbon Family $$15$$ Nitrogen Family $$16$$ Oxygen Family (or) Chalcogen family $$17$$ Halogens $$18$$ Noble gases
• Lanthanides and Actinides are Group $$3$$ elements, referred also as inner transition elements.
• Except for group $$18$$, every element in each group has the same amount of electrons in its valence shell and has the same valency. All group $$1$$ elements, for example, contain one electron in their valence shells ($$1s^1$$ ). As a result, the valency of all alkali metals is one.
• Because the elements in a group have identical valence shell electronic configurations, they have similar chemical properties.
• The physical properties of the elements in a group vary gradually, such as melting point, boiling point, and density.
• The atoms of 'group $$18$$' elements have a stable electronic configuration in their valence shells and are thus unreactive.
Periodic trends in properties:

Periodicity:
The electronic configurations of elements help us to describe the periodic recurrence of physical and chemical properties. Anything which repeats itself after a fixed interval is called periodic, and this behaviour is called periodicity. Some of the atomic properties of the elements are periodic.
Periodic properties:
Atomic radius, ionic radius, ionization energy, electronegativity, and electron affinity are called periodic properties.
The modern periodic table's primary significance is that it provides a fair conclusion of the common characteristics and trends within a group or a period, allowing us to predict the properties of any element with considerable accuracy, even if that element is unknown to us. Let's take a look at the periodic trend of some of these properties.