how is steel stronger than iron?

A pure metal has a giant metallic structure and its atoms are arranged in layers. When a force is applied, the layers can slide over each other due to its regular arrangement. In iron, the force needed to make the layers slide over each other is small which explains why many pure metals are soft.In steel, carbon and iron atoms are of different sizes distorting the layers making it harder for them to slide over eachother. More forece needed to slide the layers over eachother means steel is stronger than iron.