If the premises were true, then the conclusion would be true. (We canNOT EVEN IMAGINE a way to make the premises true and at the same time make the conclusion false.) So, the argument is VALID. Unfortunately, the premises (in the real world) are actually false. So, the argument is UNSOUND.

Consider:

The president of the United States must be younger than 35.
Elizabeth Taylor is president of the United States.
So, Elizabeth Taylor must be younger than 35.

If Elizabeth Taylor is president of the United States, then Elizabeth Taylor must be younger than 35.
Elizabeth Taylor is president of the United States.
So, Elizabeth Taylor must be younger than 35.

For either example, the logic is valid but the premises are false. For the premises to be true, all of them need to be true. But, for the premises to be false, only one need be false. So, an argument with a mixture of true and false premises is still considered to be an argument with false premises--it is false that all of the premises are true. In these examples, the conclusion is also false.

Validity is a guarantee of a true conclusion when the premises are true but offers no guarantee when the premises are false. False premises can lead to either a true or a false conclusion even in a valid argument. In these examples, bad luck rather than bad logic led to the false conclusion.