The group where all atoms have eight valence electrons in the ground state is Group 18 (VIIIa), also known as the noble gases.

Here's why:

* Valence electrons are the electrons in the outermost energy level of an atom. They are the ones involved in chemical bonding.

* Noble gases are a group of elements that are very unreactive because they already have a full outer shell of electrons, giving them a stable configuration.

* Octet rule: Most atoms strive to achieve a stable configuration like the noble gases, often by gaining, losing, or sharing electrons to have eight valence electrons.

Examples of noble gases:

* Helium (He) - 2 valence electrons (exception to the octet rule)

* Neon (Ne) - 8 valence electrons

* Argon (Ar) - 8 valence electrons

* Krypton (Kr) - 8 valence electrons

* Xenon (Xe) - 8 valence electrons

* Radon (Rn) - 8 valence electrons

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