How to find the number of protons neutrons and electrons and atomic mass when you only know the atomic number?

Atomic number is number of electrons
Electrons=proton
Atomic mass=no of proton [or no of electrons]+no of neutrons
that is basically what you need to know

Mg-26 and mg-24 are pair of isotopes. isotopes are defined as atoms of the same element having same atomic number but different mass number. i hope that was .

The population of unionid mussels decreased after zebra mussels were introduced. zebra mussels competed with the unionid mussels for food. the zebra mussels were able to displace the unionid mussels, allowing the zebra mussel population to increase  over the years. the unionid mussel population decreased because  of lack of food.