(Solved): QQ3. This question is about atoms and isotopes. (a) Atoms contain protons, neutrons and electrons. ...

QQ3. This question is about atoms and isotopes. (a) Atoms contain protons, neutrons and electrons. A lithium atom has the symbol \( { }_{3}^{7} \mathrm{Li} \) Explain, in terms of sub-atomic particles, why the mass number of this lithium atom is \( 7 . \) (b) Amounts of substances can be described in different ways. Complete the sentences. One mole of a substance is the relative formula mass in The relative atomic mass of an element compares the mass of an atom of an element with the mass of an atom of Page 4 of 49 (c) Two isotopes of oxygen are \( { }_{8}^{18} 0 \) and \( { }_{8}^{16} 0 \) Describe the similarities and differences between the isotopes \( { }_{8}^{18} \mathrm{O} \) and \( { }_{8}^{16} \mathrm{O} \) You should refer to the numbers of sub-atomic particles in each isotope.