Its valence shell is full.
Na+ and neon are isoelectronic.
The electron shell arrangement of Ceasium is 2.8.8.18.18.1
Phosphorus
The element argon (atomic number 18) has the electron configuration 1s22s22p63s23p6 which can be abbreviated [Ne] 3s23p6
Argon
Argon
Its valence shell is full.
Na+ and neon are isoelectronic.
Na+ and neon are isoelectronic.
It doesn't become an argon atom because it (Cl-) still has 17 protons, and an argon atom has to have 18 protons.
No element has the exact same election arrangement as another element. However ion can have the same election arrangement as another element. For example Chloride (Cl-) has the same configuration as Argon, and Potassium (I) (K+) also has the same configuration as argon.
Those with full electron "shells" which means that electron pairing is complete and doesn't need a second bonding arrangement. Helium, Neon, Argon, Krypton, Xenon, Radon.
The electron shell arrangement of Ceasium is 2.8.8.18.18.1
Phosphorus
The element argon (atomic number 18) has the electron configuration 1s22s22p63s23p6 which can be abbreviated [Ne] 3s23p6
Since the electron arrangement is 2,8,18, and 32, the electron arrangement for a calcium atom is 2,8, and 10.