What is the Difference Between Periods and Groups?

The difference between periods and groups in the periodic table lies in their arrangement and the properties they represent:

• Periods: These are horizontal rows of the periodic table. A new period begins when a new principal energy level begins filling with electrons. Elements in the same period have the same number of electron shells. Periods are often referred to as "families" or "orbital types".
• Groups: These are vertical columns of the periodic table, based on the organization of the outer shell electrons. Elements in the same group have the same number of electrons in their outermost shells. Groups are also known as "families".

There are a total of 18 groups, with groups 1-2 being 1A and 2A, respectively, and groups 3-8 being 3A through 8A. The periodic table is arranged in order of atomic number. The two numbering systems for groups are used to differentiate between the types of elements and their properties.

Comparative Table: Periods vs Groups

Here is a table summarizing the differences between periods and groups in the periodic table:

In summary, periods are horizontal rows in the periodic table, where elements have the same number of electron shells, and the number of protons in the atomic nucleus increases by 1 for each next element in the period. Groups, on the other hand, are vertical columns in the periodic table, where elements have the same number of electrons in the outermost shell, leading to similar chemical properties.