Question

I need to find the bond type of cu-cu-cu-cu
The electronegativity is 1.75
Would this become an ionic bond ?

Answer 1

The rule of thumb is that for an electronegativity difference of about 1.8 or so the bond is about 50% ionic/50% covalent character.

Answer 2

But I don't know how you arrived at 1.75. What you have is a metallic bond.