1. Atomic number of an element is the number of neutrons present in the nucleus of the atom.   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. Isotopes have same atomic number.   True   False   5. In a neutral atom, the number of electrons and protons is equal.   True   False   6. One atom of carbon and two atoms of oxygen combine to form a molecule of carbon dioxide [CO2].   True   False   7. The smallest atom is that of hydrogen.   True   False