1. x y z
(1s + 1s) σ

2. (1s - 1s) sσ*

3. (2pz + pz) 2pσ

4. (pz - pz) 2pσ*

5. (2px + 2px) 2pπ

6. (2px - 2px) 2pπ*

7. (2py + 2py) 2pπ

8. (2py - 2py) π*

9. 1sσ*
1sσ
(1sσ)2 (1sσ*)2

10. H2+
1sσ* ↑
1sσ
(1sσ)2 (1sσ*)2

11. H2
1sσ*
↑ ↓
1sσ
(1sσ)2 (1sσ*)2

12. He2+
1sσ* ↑
↑ ↓
1sσ
(1sσ)2 (1sσ*)2

13. He2+ H2–
1sσ* ↑
↑ ↓
1sσ
(1sσ)2 (1sσ*)2

14. He2
1sσ*
↑ ↓
↑ ↓
1sσ)
(1sσ)2 (1sσ*)2

16. 2sσ
1sσ*
1sσ)
(1sσ)2 (1sσ*)2 (2sσ)2 (2pσ)2 (2pπ)4 (2pπ*)4 (2pσ*)2 (2sσ*)2

17. 2sσ*
2sσ
1sσ*
1sσ)
(1sσ)2 (1sσ*)2 (2sσ)2 (2pσ)2 (2pπ)4 (2pπ*)4 (2pσ*)2 (2sσ*)2

19. 2p
2pσ
2sσ*
2sσ
1sσ*
1sσ)
(1sσ)2 (1sσ*)2 (2sσ)2 (2pσ)2 (2pπ)4 (2pπ*)4 (2pσ*)2 (2sσ*)2

20. 2pσ* 2p
2pσ
2sσ*
2sσ
1sσ*
1sσ)
(1sσ)2 (1sσ*)2 (2sσ)2 (2pσ)2 (2pπ)4 (2pπ*)4 (2pσ*)2 (2sσ*)2

21. 2pσ*
2pπ
2pσ
2sσ*
2sσ
1sσ*
1sσ)
(1sσ)2 (1sσ*)2 (2sσ)2 (2pσ)2 (2pπ)4 (2pπ*)4 (2pσ*)2 (2sσ*)2

22. 2pσ*
2pπ*
2pπ
2pσ
2sσ*
2sσ
1sσ*
1sσ)
(1sσ)2 (1sσ*)2 (2sσ)2 (2pσ)2 (2pπ)4 (2pπ*)4 (2pσ*)2 (2sσ*)2

23. 2pσ*
2pπ*
2pπ
2pσ
2sσ*
2sσ
1sσ*
1sσ)
(1sσ)2 (1sσ*)2 (2sσ)2 (2pσ)2 (2pπ)4 (2pπ*)4 (2pσ*)2 (2sσ*)2

25. O2 2pσ* 2pπ* 2pπ 2pσ 2pπ 2pσ 2sσ* 2sσ 1sσ* 1sσ)
(1sσ)2 (1sσ*)2 (2sσ)2 (2pσ)2 (2pπ)4 (2pπ*)4 (2pσ*)2 (2sσ*)2

26. (1sσ)2 (1sσ*)2 (2sσ)2 (2pσ)2 (2pπ)4 (2pπ*)4 (2pσ*)2 (2sσ*)2↑ ↑
↑ ↓
2pσ
↑ ↓
↑ ↓
2pπ
↑ ↓
2sσ*
2sσ
↑ ↓
1sσ*
↑ ↓
↑ ↓
1sσ)
(1sσ)2 (1sσ*)2 (2sσ)2 (2pσ)2 (2pπ)4 (2pπ*)4 (2pσ*)2 (2sσ*)2

29. O2 2pσ* 2pπ* 2pπ 2pσ 2sσ* 2sσ 1sσ* 1sσ)
(1sσ)2 (1sσ*)2 (2sσ)2 (2pσ)2 (2pπ)4 (2pπ*)4 (2pσ*)2 (2sσ*)2

30. O2 2pσ* 2pπ* 2pσ 2pπ 2sσ* 2sσ 1sσ* 1sσ)↑ ↑
↑ ↓
2pσ
↑ ↓
↑ ↓
2pπ
↑ ↓
2sσ*
2sσ
↑ ↓
1sσ*
↑ ↓
↑ ↓
1sσ)
(1sσ)2 (1sσ*)2 (2sσ)2 (2pσ)2 (2pπ)4 (2pπ*)4 (2pσ*)2 (2sσ*)2

32. O2 2pσ* 2pπ* 2pσ 2pπ 2sσ* 2sσ 1sσ* 1sσ)↑ ↑
↑ ↓
2pσ
↑ ↓
↑ ↓
2pπ
↑ ↓
2sσ*
2sσ
↑ ↓
1sσ*
↑ ↓
↑ ↓
1sσ)
(1sσ)2 (1sσ*)2 (2sσ)2 (2pσ)2 (2pπ)4 (2pπ*)4 (2pσ*)2 (2sσ*)2

33. O2 2pσ* 2pπ* 2pπ 2pσ 2sσ* 2sσ 1sσ* 1sσ)↑ ↑
2pπ
↑ ↓
↑ ↓
↑ ↓
2pσ
↑ ↓
2sσ*
2sσ
↑ ↓
1sσ*
↑ ↓
↑ ↓
1sσ)
(1sσ)2 (1sσ*)2 (2sσ)2 (2pσ)2 (2pπ)4 (2pπ*)4 (2pσ*)2 (2sσ*)2

34. O2 2pσ* 2pπ* 2pπ 2pσ 2sσ* 2sσ 1sσ* 1sσ)↑ ↑
2pπ
↑ ↓
↑ ↓
↑ ↓
2pσ
↑ ↓
2sσ*
2sσ
↑ ↓
1sσ*
↑ ↓
↑ ↓
1sσ)
(1sσ)2 (1sσ*)2 (2sσ)2 (2pσ)2 (2pπ)4 (2pπ*)4 (2pσ*)2 (2sσ*)2

36. O2 2pσ* 2pπ* 2pπ 2pσ 2sσ* 2sσ 1sσ* 1sσ)↑ ↑
2pπ
↑ ↓
↑ ↓
↑ ↓
2pσ
↑ ↓
2sσ*
2sσ
↑ ↓
1sσ*
↑ ↓
↑ ↓
1sσ)
(1sσ)2 (1sσ*)2 (2sσ)2 (2pσ)2 (2pπ)4 (2pπ*)4 (2pσ*)2 (2sσ*)2

37. Separate atoms ↑ ↑

38. At the bond separation the bonding and antibonding orbitals split apart in energy↑ ↑

39. The electrons pair up in the lower level – energy is gained - relative to the separate atoms and a stable molecule is formed σ* ↑ ↑ ↓↑ σ

40. σ*
E = α - β ↓↑ σ
E = α + β

41. Note β the stabilisation energy is –ve↓↑
E = α + β
Note β the stabilisation energy is –ve

42. ↑ σ* ↑ σ

43. ↓↑ σ* σ

44. H2+ σ* ↑ σ

50. The wave function is usually represented by ψ

51. The electron density is given by ψ2

52. probability = ψ2
Electron Density
Radius r