To determine which option leads to the formation of an ionic bond with [tex]\( Hg^{2+} \)[/tex], let's analyze each option:
1. The attraction of a noble gas:
- Noble gases are known to be chemically inert due to their complete valence electron shell. They typically do not form bonds with other elements, including ionic bonds.
2. The attraction of an [tex]\( NH_4^+ \)[/tex] ion:
- The [tex]\( NH_4^+ \)[/tex] ion, also known as the ammonium ion, is a positively charged ion (cation). Since both [tex]\( Hg^{2+} \)[/tex] and [tex]\( NH_4^+ \)[/tex] are cations, they will repel each other rather than form an ionic bond, as ionic bonds form between oppositely charged ions.
3. The attraction of a group 1 element:
- Group 1 elements, such as sodium (Na), potassium (K), and lithium (Li), form cations with a [tex]\( +1 \)[/tex] charge when they ionize (e.g., [tex]\( Na^+ \)[/tex], [tex]\( K^+ \)[/tex]). Similar to the [tex]\( NH_4^+ \)[/tex] ion, these cations will not form ionic bonds with [tex]\( Hg^{2+} \)[/tex], since both have positive charges.
4. The attraction of an [tex]\( SO_4^{2-} \)[/tex] ion:
- The sulfate ion, [tex]\( SO_4^{2-} \)[/tex], is an anion with a [tex]\( -2 \)[/tex] charge. Since [tex]\( Hg^{2+} \)[/tex] is a cation with a [tex]\( +2 \)[/tex] charge, the positive charge of [tex]\( Hg^{2+} \)[/tex] will attract the negative charge of [tex]\( SO_4^{2-} \)[/tex], leading to the formation of an ionic bond.
Thus, the correct choice that leads to the formation of an ionic bond with [tex]\( Hg^{2+} \)[/tex] is:
- The attraction of an [tex]\( SO_4^{2-} \)[/tex] ion
So, the answer is [tex]\( \boxed{4} \)[/tex].
