The electronic configuration of an element is 2, 8, 8. It belongs to group

Question

Prepp Team · Accepted Answer

Understanding Electronic Configuration and Periodic Table Groups

The electronic configuration of an element provides information about how electrons are arranged in different energy shells around the nucleus. This arrangement is key to understanding the element's properties and its position in the periodic table, specifically its group and period.

Determining the Atomic Number

The given electronic configuration is 2, 8, 8. This sequence represents the number of electrons in the first, second, and third energy shells, respectively. The total number of electrons in a neutral atom is equal to its atomic number. Let's sum the electrons:

Total electrons = Electrons in 1st shell + Electrons in 2nd shell + Electrons in 3rd shell

Total electrons = $2 + 8 + 8 = 18$

So, the atomic number of this element is 18. The element with atomic number 18 is Argon (Ar).

Determining the Group Number

The group number of an element in the periodic table is largely determined by the number of valence electrons, which are the electrons in the outermost shell.

In the given electronic configuration (2, 8, 8), the outermost shell is the third shell (M shell), and it contains 8 electrons. These are the valence electrons.

For elements in the s-block and p-block (which constitute Groups 1, 2, and 13-18), the group number can often be determined based on the valence electrons:

For elements in Group 1 and 2 (s-block), the group number is equal to the number of valence electrons.
For elements in Groups 13-18 (p-block), the group number is typically 10 + the number of valence electrons (if the outermost shell is the p-subshell and is being filled). However, a simpler way for the later groups is to recognize the filling of the outermost shell.

An element with 8 valence electrons (octet rule satisfied) in its outermost shell (except for Helium) is a noble gas. Noble gases are located in Group 18 of the periodic table. The configuration 2, 8, 8 corresponds to Argon, which is a noble gas.

Let's look at how valence electrons relate to group numbers for elements beyond the first few periods:

Valence Electrons	Typical Group Number (for elements with > 1 shell)
1	1
2	2
3	13
4	14
5	15
6	16
7	17
8	18

Since the element has 8 valence electrons, it belongs to Group 18.

Conclusion

The element with electronic configuration 2, 8, 8 has 18 electrons and 8 valence electrons. This places it in Group 18 of the periodic table.

Revision Table: Key Concepts

Concept	Explanation
Electronic Configuration	Distribution of electrons in energy shells and subshells.
Atomic Number	Total number of protons in the nucleus (equals total electrons in a neutral atom).
Valence Electrons	Electrons in the outermost energy shell.
Group Number	Column in the periodic table; often related to the number of valence electrons. Elements in the same group have similar chemical properties.
Period Number	Row in the periodic table; corresponds to the highest occupied energy shell.

Additional Information: Periodic Trends and Group 18

Group 18 elements are known as the noble gases. They include Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe), Radon (Rn), and Oganesson (Og). Their general electronic configuration is $ns^2 np^6$ (except Helium, which is $1s^2$), resulting in a stable octet (or duplet for He) in their outermost shell. This stable configuration makes them very unreactive under normal conditions, which is why they are called "noble" gases.

The electronic configuration 2, 8, 8 corresponds specifically to Argon (Ar), which is in the 3rd period (because it has electrons in the 3rd shell) and Group 18.