What type of bond forms between atoms with very large differences in
electronegativity?

Ionic or electrovalent bond

Explanation:

The electronegativity of an atom determines to what extent an atom would attract an electron towards it. So, they can form combine.

The nature of chemical bonding depends upon the difference between the electronegativity of the combining atoms.

When the electronegativity difference is

                               <  0.4                  -  forms non-polar covalent bonds

                     between  0.4 and 1.7 - polar covalent bonds

                                > 1.7                   - ionic bond

Hence, when there is a large difference between the electronegativity of atoms, it forms ionic bonds.

i would think klcio3