A. Fill in the blanks:
1. An _________ is a pure substance that cannot be broken down by chemical methods into simpler components.
2. An___________ is the smallest particle of an element that still has the same properties of that element.
3. There are a total of __________ elements.
4. A ___________ is a molecule made of atoms from different elements.
5. ___________ in compounds happen when chemical bonds are created or destroyed​