In Class Problems - 11/2/00

1.) Write ground-state electron configurations for the atoms Se, P, Fe, Tc, Ho and the ions Be⁺, Ne²⁺, Mg⁺, N^2-, I^-, S^2-, As⁺. Which do you expect will be paramagnetic due to the presence of unpaired electrons?

2.) Suppose that the spin quantum number did not exist, so that only one electron could occupy each orbital of a many-electron atom. Give the atomic numbers of the first three noble gases.

3.) Arrange the following six atoms or ions in order of size, from smallest to largest: K, F⁺, Rb, Co²⁵⁺, Br, F, Rb^-.

*4.) a.) The nitrogen atom has one electron in each of the 2p_x, 2p_y, and 2p_z orbitals. By using the form of the angular wave functions, show that the total electron density, y²(2p_x) + y²(2p_y) + y²(2p_z), is spherically symmetric (that is, it is independent of the angles q and f). The neon atom, which has two electrons in each 2p orbital, is also spherically symmetric. Note:

y(p_x) = (3/4p)^1/2 sinq cosj

y(p_y) = (3/4p)^1/2 sinq sinj

y(p_z) = (3/4p)^1/2 cosq

b.) The same result as in part (a) applies to d orbitals, so that a filled or half filled subshell of d orbitals is spherically symmetric. Identify the spherically symmetric atoms or ions among the following: F^-, Na, Si, S^2-, Ar⁺, Ni, Cu, Mo, Rh, Sb, W, Au.