List the following bonds in order of increasing ionic character. (Enter your answer in the format H-O for the hydrogen-to-oxygen bond in H2O. Use the appropriate <, =, or > symbol to separate substances in the list.)
the sodium-to-fluorine bond in Na-F
the potassium-to-oxygen bond in K2O
the lithium-to-lithium bond in Li
the sulfur-to-oxygen bond in SO2
the potassium-to-bromide bond in K-Br