Answer:
Electron Configurations - Solutions
Note: The electron configurations in this worksheet assume that lanthanum (La)
is the first element in the 4f block and that actinium (Ac) is the first element in the
5f block. If your periodic table doesn’t agree with this, your answers for elements
near the f-orbitals may be slightly different.
1) sodium 1s2
2s2
2p6
3s1
2) iron 1s2
2s2
2p6
3s2
3p6
4s2
3d6
3) bromine 1s2
2s2
2p6
3s2
3p6
4s2
3d104p5
4) barium 1s2
2s2
2p6
3s2
3p6
4s2
3d104p6
5s2
4d105p6
6s2
5) neptunium 1s2
2s2
2p6
3s2
3p6
4s2
3d104p6
5s2
4d105p6
6s2
4f145d106p6
7s2
5f5
6) cobalt [Ar] 4s2
3d7
7) silver [Kr] 5s2
4d9
8) tellurium [Kr] 5s2
4d105p4
9) radium [Rn] 7s2
10) lawrencium [Rn] 7s2
5f146d1
11) 1s2
2s2
2p6
3s2
3p4
sulfur
12) 1s2
2s2
2p6
3s2
3p6
4s2
3d104p6
5s1
rubidium
13) [Kr] 5s2
4d105p3
antimony
14) [Xe] 6s2
4f145d6
osmium
15) [Rn] 7s2
5f11 einsteinium
16) 1s2
2s2
2p6
3s2
3p6
4s2
4d104p5 not valid (take a look at “4d”)
17) 1s2
2s2
2p6
3s3
3d5
not valid (3p comes after 3s)
18) [Ra] 7s2
5f8
not valid (radium isn’t a noble gas)
19) [Kr] 5s2
4d105p5 valid
20) [Xe] not valid (an element can’t be its own electron configuration)
