Types of Bonds can be predicted by calculating the difference in electronegativity.
If, Electronegativity difference is,
Less than 0.4 then it is Non Polar Covalent
Between 0.4 and 1.7 then it is Polar Covalent
Greater than 1.7 then it is Ionic
For Li and O,
E.N of Oxygen = 3.44
E.N of Lithium = 0.98
________
E.N Difference 2.46 (Ionic Bond)
For Cl and F,
E.N of Fluorine = 3.98
E.N of Chlorine = 3.16
________
E.N Difference 0.82 (Mildly Polar Covalent Bond)
For Ca and S,
E.N of Sulfur = 2.58
E.N of Calcium = 1.00
________
E.N Difference 1.58 (Polar Covalent Bond)
