Why is platinum in a catalytic converter a element?

Answer 1

When a substance is an element, every single atom in that substance has the same number of protons. For instance, graphite is simply elemental carbon because every atom in graphite is a carbon atom. Water is not an element because each molecule of water contains two hydrogen atoms and one oxygen atom. Pure platinum is made up of many atoms with exactly 78 protons each bound together.

Platinum atoms can be found in a few forms. To list a few, it can be combined with other metals in an alloy, it can be combined with certain atoms as a salt (platinum dioxide for instance), it can be found in a solution as an ion (Pt2+ for example), and it can be found as a pure sample of just plain old platinum. This is the case in your catalytic converter.

When atoms bond chemically, their electrons interact. This changes their properties. In the catalytic converter, only platinum in the elemental form has the right chemical properties to change carbon monoxide into carbon dioxide, for example. This is why manufacturers use elemental platinum instead of something else.

For an example of platinum that's not elemental, platinum dioxide is used as a different catalyst to make hydrogenated vegetable oils. It's not an element because it is bound to atoms with different numbers of protons (oxygen atoms).

Hope this helps!