Answer:
c) Fluorine forms an ionic bond.
Step-by-step explanation:
A chemical bond in which a complete transfer of valence electrons between the atom occurs called ionic bond. It is a combination of two oppositely charged atoms.
In an ionic bond metals loses its valence electrons to become a positively charged ion called cation, whereas the nonmetal accepts those electrons to become a negatively charged ion called anion.
There are four elements given;
1) Helium
There are only two electrons in helium which occupies in the K shell which is also the valence shell of the atom. And K shell maximum contain two electron. It means it has complete shell of electrons so it does not bond with other element.
2) Neon
It has also compete shell of electrons that is 8. It is an inert gas which does not bond with other element.
3) Fluorine
It has 7 electrons in its outermost shell, to complete its octet it gains one electron. That means there is a complete acceptance of an electron which determines that it forms an ionic bond.
Sodium has 1 electron in its outermost shell. So it loses its electron and forms cation. Where as Fluorine has 7 electrons so it gains the lose electron to form anion. And thus formed Sodium Fluoride an ionic bond compound.
4)Carbon
Carbon has 4 electrons in its outermost shell. It can neither gain nor lose electrons to complete its octet. It only shares electrons with other element. And sharing of electrons known as covalent bond.