6. why is there no overall charge on an atom?
- number of protons is equal to number of electrons
- number of protons is equal to the number of neutrons
- mass number can be divided by two
7. why is the extraction of copper expensive?
- takes a lots of time
- many steps are involved
- copper is very reactive
- its a batch process
8. the atomic number of an atom is the number of...
- protons
- neutrons
- electrons
