What is the mass of an atom?

What is an Isotope?

Is the mass number smaller or bigger than the atomic number?

What is an atomic number?

Where is the atomic and mass number on a chemical symbol?

What is an atom with a full outer shell?

Why do atoms react with other atoms.

What is an electron strucutre?

What is the number of shells in an atom the same as?

What is the number of electrons in the final outer shell of an element the same as?