Why can't chlorine and bromine form a covalent compound?
They are highly electronegative. They can only accept electrons, but they can't lose them, as this would require a lot of energy. They have positive ionisation enthalpy value and negative electron gain enthalpy.
But chlorine, bromine, fluorine.... They form molecules which are covalent too... I mean like Cl2, Br2....
Yes, they do form covalent compounds, for example in CCl4, there are four covalent bonds, and in CH2Br, CH3Br, etc. I forgot that it's hard for them to lose electrons, but they can share them, as in Carbon tetrachloride.
So it also requires a lot energy when they form CH3Br and CH2Br?
They do, it is called bromine monochloride.
Oh I see thanks!
Separate names with a comma.