1. Atomic weight of an element is the mass of an atom of that element in grams.   True   False   2. An element is a substance made up of different kinds of atoms.   True   False   3. Isotopes have same atomic number.   True   False   4. The nucleus consists of protons and neutrons and is negatively-charged.   True   False   5. Since an atom of the element sodium contains 11 protons and 12 neutrons, its atomic number is 23.   True   False   6. One atom of carbon and two atoms of oxygen combine to form a molecule of carbon dioxide [CO2].   True   False   7. An atom consists of a central nucleus containing positively-charged protons and negatively-charged neutrons.   True   False