• The element vanadium has two isotopes, 51V  and 50V   and a relative atomic mass of 50.94.
            (a)    Define the term isotope.
                    ……………………………………………………………………………………….
                    ……………………………………………………………………………………….
            (b)    State and explain which is the more abundant isotope.
                    ……………………………………………………………………………………….
                    ……………………………………………………………………………………….
            (c)    State the name and the mass number of the isotope relative
                    to which all atomic masses are measured.
                    ……………………………………………………………………………………….

  • The diagram below (not to scale) represents some of the electron energy levels in the hydrogen atom.
              ________________________________   n = 
              ________________________________   n = 6
              _________________________________   n = 5

              _________________________________   n = 4


              ________________________________   n = 3



              ________________________________   n = 2




              ________________________________   n = l

            (i)       Draw an arrow on the diagram to represent the electron
                      transition for the ionization of hydrogen.
                      Label this arrow A.
            (ii)      Draw an arrow on the diagram to represent the lowest
                      energy transition in the visible emission spectrum.
                      Label this arrow B.
                      (Total 4 marks)

Answer : (i)    line starting at n = 1;
                    line finishing at n = ∞ (not above ∞);
                    upward arrow;    2 max
                    3 correct [2], 2 correct [1].
              (ii)    Line from n = 3 to n = 2;
                    Arrow pointing downward (in any transition);    2

  • Which statement is correct for the emission spectrum of the hydrogen atom?
        A.    The lines converge at lower energies.
        B.    The lines are produced when electrons move from
                lower to higher energy levels.
        C.    The lines in the visible region involve electron transitions into
                the energy level closest to the nucleus.
        D.    The line corresponding to the greatest emission of energy
                 is in the ultraviolet region.
        (Ans : D )

  • Which types of bonding are present in CH3CHO in the liquid state?
        I.    Single covalent bonding
        II.    Double covalent bonding
        III.    Hydrogen bonding
        A.    I and II only
        B.    I and III only
        C.    II and III only
        D.    I, II and III
        (Ans: A )

  • (a)    State a physical property that is different for isotopes of an element.
                    .......................................................................................................
          (b)    Chlorine exists as two isotopes, 35Cl and 37Cl. The
                  relative atomic mass of chlorine is 35.45.
                  Calculate the percentage abundance of each isotope.
                    .....................................................................................................................................
                    .....................................................................................................................................
                    .....................................................................................................................................
                    .....................................................................................................................................
Ans : (a)    mass/density/for gases: rate of effusion or diffusion/
                melting point/boiling point   
                Do not accept mass number.
        (b)    if 35Cl = x, then (x = 35.00) + (1 – x) 37.00 = 35.45
                Award [1] for set up.
                therefore, x = 0.775;    2
                35Cl = 77.5% and 37Cl = 22.5%;
                (need both for mark);