What does the statment mean. the properties of salts are different from the properties of the elements that go into making them mean?

Think of it this way,
Mix Iron and sulphur in a bowl. How do you separate them? Use a magnet right. Yes.

Now, mix the iron and sulphur together but know, heat them up. Let them cool for a while. After that, use a magnet to separate. You cant. This is because the compound (FeS) now has a different property from its original components.

Apply this theory onto salts.

Is a logical series of steps