1. Nucleus always contains a neutron.   True   False   2. In a neutral atom, the number of electrons and protons is equal.   True   False   3. The atom is mainly empty.   True   False   4. Isotopes have similar chemical properties.   True   False   5. Isotopes have same atomic weight.   True   False   6. Atomic number of an element is the number of neutrons present in the nucleus of the atom.   True   False   7. Since an atom of the element sodium contains 11 protons and 12 neutrons, its atomic number is 23.   True   False