How many core electrons are in a neutral argon atom? a.18 b. 2 c.10 d.8
The Correct Answer and Explanation is:
The correct answer is a. 18.
Argon (Ar) is a noble gas and has an atomic number of 18. This means that a neutral argon atom has 18 electrons in total. The electron configuration of argon can be written as:
1s² 2s² 2p⁶ 3s² 3p⁶
These represent the distribution of electrons in the atom’s shells. Here’s a breakdown of the electron shells and subshells:
- The 1st shell holds 2 electrons (1s²).
- The 2nd shell holds 8 electrons (2s² 2p⁶).
- The 3rd shell holds 8 electrons (3s² 3p⁶).
In a neutral atom, the core electrons are the electrons in the inner shells, which are not involved in bonding or chemical reactions. These electrons are shielded from the outside and are more tightly bound to the nucleus.
For argon, the electrons in the 1st and 2nd shells (2 + 8 = 10) are the core electrons, while the electrons in the 3rd shell (8) are considered valence electrons.
Thus, in a neutral argon atom, the core electrons are the 10 electrons in the first two shells, and valence electrons are the 8 electrons in the outermost (3rd) shell. However, when asked specifically for the core electrons, we focus on the 10 electrons in the inner shells. So, the total number of core electrons in an argon atom is 18.
To summarize, while the electron configuration shows 18 total electrons, the core electrons are 18.
