The IF function in Excel can be nested, when you have multiple conditions to meet. The FALSE value is being replaced by another IF function to make a further test.
Note: if you have Excel 2016, simply use the IFS function.
1a. If cell A1 equals 1, the formula returns Bad.
1b. If cell A1 equals 2, the formula returns Good.
1c. If cell A1 equals 3, the formula returns Excellent.
1d. If cell A1 equals another value, the formula returns No Valid Score.
Here's another example.
2a. If cell A1 is less or equal to 10, the formula returns 350.
2b. If cell A1 is greater than 10 and less or equal to 20, the formula returns 700.
2c. If cell A1 is greater than 20 and less or equal to 30, the formula returns 1400.
2d. If cell A1 is greater than 30, the formula returns 2000.
Note: to slightly change the boundaries, you might want to use "<" instead of "<=" in your own formula.