I agree on most of Yomen Atassi's answer, however I would like to "correct/clarify" the formula of the percent ionic character. The following is the one cited by him, which is the one also reported in several sites in the internet:
Percent ionic character = (1 − e^(−(Δχ/2)2))×100
However applying this equation to real cases results in incoherent percentages (negative values larger than 100).
Checking the source of Pauling's equation (Pauling L. The nature of the chemical bond. 3rd ed. 1960. Pag. 98), I realized that the mathematical expression is different. This is the one cited in the book:
Percent ionic character = (1 − e^(−1/4(Δχ^2)))×100
The last expression provides consistent values which are in agreement with values reported by Pauling and other authors.
If you want to apply Pauling's equation for the calculation of "percent of ionic character" (using electronegativity differences, Δχ), consider to use the later equation.