Final answer:
Humans were able to use elemental copper before elemental tin because copper occurs in nature in a directly usable metallic form, while tin occurs primarily as an oxide. Once humans developed the technology to extract tin from its oxide form, they were able to create bronze by alloying copper with tin.
Step-by-step explanation:
The reason humans were able to use elemental copper before elemental tin is because copper is one of the few metals that can be found in nature in a directly usable metallic form, while tin occurs primarily as tin (IV) oxide. This means that copper was readily available to early humans, allowing them to use it for various purposes such as making tools and weapons.
On the other hand, tin occurs in nature as an oxide and needed to be processed before it could be used. The heat of formation for tin (IV) oxide is higher compared to copper (II) oxide, which means that more energy is required to produce tin from its oxide form. This could explain why humans were able to use elemental copper before they were able to use elemental tin.
Once humans developed the technology to extract tin from its oxide form, they were able to create bronze by alloying copper with tin, which opened up new possibilities in terms of toolmaking and other applications.