An atom of an element in the ground state contains 8 valence electrons. The element is considered as a

Step 1: Analyze the question We are told an atom in its ground state has 8 valence electrons (electrons in the outermost shell). We need to decide which type of element this describes.

Step 2: The concept The number of valence electrons tells us the group of the element:

• 1 or 2 valence electrons: usually metals (Groups 1 and 2)
• 3 to 6: mixed (metals, semi-metals, non-metals)
• 7: halogens (Group 17)
• 8: noble gases (Group 18), which have a full outer shell (octet)

Step 3: Solution

• Metals (A): They usually have 1 to 3 valence electrons and tend to lose them. They do not have 8.
• Semi-metals (B): These, such as silicon and germanium, have 3 to 5 valence electrons.
• Halogens (D): They have 7 valence electrons and need one more to complete their octet.
• Noble gases (C): Neon (2,8), argon (2,8,8), krypton and xenon have 8 electrons in the outermost shell. This stable octet makes them chemically inert.

(Helium is the exception with 2 electrons, but it is still a noble gas because its only shell is full.)

Step 4: Answer The element with 8 valence electrons is a noble gas, which is option C.

Tip: Remember "8 is great": a full octet means stable and unreactive. Group number minus 10 gives the valence electrons for Groups 13 to 18 (Group 18 gives 8; Group 17 gives 7, the halogens).