1. An atom consists of a central nucleus containing positively-charged protons and negatively-charged neutrons.   True   False   2. Since an atom of the element sodium contains 11 protons and 12 neutrons, its atomic number is 23.   True   False   3. The atom is mainly empty.   True   False   4. The smallest atom is that of hydrogen.   True   False   5. In a neutral atom, the number of neutrons and protons is equal.   True   False   6. Isotopes differ in the number of neutrons they have in their nucleus.   True   False   7. The number of electrons in a neutral atom is equal to its atomic number.   True   False