Australian School of Abu Dhabi
Unit Atomic Structure
Worksheet 2 Electron configuration
1. Draw and label (using the letters a, b and c) on the energy level diagram below:
(a) the electron transition which will give the third line in the visible series of the hydrogen
emission spectrum.
(b) the electron transition which will give the third line in the ultraviolet series of the hydrogen
emission spectrum.
(c) the transition that relates to the ionisation energy of a hydrogen atom.
2. State the full electron configuration of:
(a) a free nitrogen atom
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Australian School of Abu Dhabi
(b) an uncombined bromine atom
(c) [Ar]4s23d5
(d) Fe3+
(e) an uncombined chromium
(f) Ge2+
3. Complete the boxes using arrows to represent electrons.
4. Explain why it is important to label the x,y and z axes when drawing out the shape of a p orbital.
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5. Explain why a potassium atom contains an electron in a 4s orbital with no electrons in a 3d orbital
whereas a copper(I) ion, Cu+ has the electronic configuration [Ar]3d10 with no electrons in the 4s
orbital.
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Answers
1
.
2.
(a) (N) 1s22s22p3
(b) (Br) 1s22s22p63s23p64s23d104p5
(c) 1s22s22p63s23p64s23d5
(d) (Fe3+) 1s22s22p63s23p63d5
(e) (Cr) 1s22s22p63s23p64s13d5
(f) (Ge2+) 1s22s22p63s23p64s23d10
3.
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4. The three p orbitals are of equal energy and are orthogonal to each other. The px orbital lies along the
x-axis, py lies along the y-axis and pz lies along the z-axis.
5. For the free atom the 4s sub-energy level is lower than the 3d sub-energy level and so is filled first.
Once an ion is formed the positive nucleus attracts the electron energy levels more strongly and the 3d
sub-level becomes lower in energy than the 4s sub-level so the 4s electron is removed leaving a full 3d
sub-energy level.
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