1.  Remember that ionization energy increases across the periodic table and decreases down.
    (a) Mg - see above
    (b) C - see above
    (c) Na⁺ - Second ionization energy always higher than first.

2. Single slit experiment (a big dot in the middle and fringes to the side) shows light defracting, which is a characterisic of waves.  The double slit experiment (zebra stripes) illustrates light interfering, which is also a characteristic of waves.

3.  The space that electrons occupy is small compared the size of their wavelength while the space people occupy is big compared to our wavelengths.

4.     (a) When a photon is absorbed, an electron moves from the state it is in to a higher energy state.
        (b) E(1) = -2.178 x 10^-18 J and E(2) = -2.178 x 10^-18 J
             E(2) - E(1) = -2.178 x 10^-18 J - (-2.178 x 10^-18 J ) = 1.63 x 10^-18 J
        (c) wavelength = hc/E = 121 nm
        (d) IE is from the ground state to above the n = infinity line
        (e) The observed absorption lines are fingerprints of the elements