How to write the electron configuration of an element? | ChemTok (2023)

Electron configuration is another basic concept you have to be heard when learning chemistry. As I think it lays the foundation for almost every part of chemistry. In this chapter, I’m going to tell you how to write the electron configuration of an element correctly.

So, let’s dive in.

Firstly, let’s see what an electron configuration of an element is.

What is an electron configuration of an element?

An electron configuration is a standard notation that describes how electrons have been distributed in their atomic orbitals. It shows all electrons in each subshell with the energy level number where the electrons are located. The electron configuration of an element helps to determine the valency of that element, predict the atomic spectra, and to understand its properties since elements with similar electron configurations tend to exhibit similar properties.

Now, let’s see how to write the electron configuration of an element.

How to write the electron configuration of an element?

When writing the electron configurations, there are some principles that you have to keep in mind. The first one is the Auf Bau principle.

The Auf Bau principle

According to this principle, electrons are filled to the energy levels around the nucleus from the orbital, which has the lowest energy or the nearest orbital to the nucleus, to orbitals in the order of increasing energy. To clarify, this can simply represent as follows.

Thus, the energy of orbitals increases in the following order.

1s< 2s< 2p< 3s< 3p< 4s< 3d< 4p< 5s< 4d< 5p< 6s< 4f< 5d< 6p< 7s……………

Then, let’s see how to write the electron configuration of an element step by step.

According to the number of electrons present in the atom, write the orbitals respectively as the inner orbitals are completely filled with electrons and in order from closest to the nucleus to away from the nucleus. Moreover, you may or may not separate orbitals by commas.

So, let’s go through an example.

Phosphorus- 15

• 1s² 2s² 2p⁶ 3s² 3p³
• 1s², 2s², 2p⁶, 3s², 3p³
• 1s² 2s² 2p⁶ 3s² 3p³

In general, the most convenient way is to write the electron sequence without separating the orbitals by separating the main energy levels with blanks.

1. H:

1s¹

2. He:

1s²

3. Li:

1s² 2s¹

4. Be:

1s² 2s²

5. B:

1s² 2s² 2p¹

6. C:

1s² 2s² 2p²

7. N:

1s² 2s² 2p³

8. O:

1s² 2s² 2p⁴

9. F:

1s² 2s² 2p⁵

10. Ne:

1s² 2s² 2p⁶

11. Na:

1s² 2s² 2p⁶ 3s¹

12. Mg:

1s² 2s² 2p⁶ 3s²

13. Al:

1s² 2s² 2p⁶ 3s² 3p¹

14. Si:

1s² 2s² 2p⁶ 3s² 3p²

15. P:

1s² 2s² 2p⁶ 3s² 3p³

16. S:

1s² 2s² 2p⁶ 3s² 3p⁴

17. Cl:

1s² 2s² 2p⁶ 3s² 3p⁵

18. Ar:

1s² 2s² 2p⁶ 3s² 3p⁶

19. K:

1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹

20. Ca:

1s² 2s² 2p⁶ 3s² 3p⁶ 4s²

21. Sc:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹ 4s²

22. Ti:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d² 4s²

23. V:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d³ 4s²

24. Cr:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁴ 4s²

• Here, the electron configuration of (n-1) d⁴ ns² is unstable. Thus, an electron from the s orbital migrates to the d orbital and makes (n-1) d⁵ ns² electron configuration. It is a stable configuration compared with the early one. So, we can write the correct electron configuration of Cr as follows.

Cr: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵ 4s¹

25. Mn:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵ 4s²

26. Fe:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶ 4s²

27. Co:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁷ 4s²

28. Ni:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁸ 4s²

29. Cu:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁹ 4s²

• Here, the electron configuration of (n-1) d⁹ ns² is unstable, and therefore an electron from the s orbital migrates to the d orbital and forms a more stable (n-1) d¹⁰ ns¹ electron configuration. So, we can write the actual electron configuration of Cu as follows.

Cu: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s¹

30. Zn:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s²

31. Ga:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p¹

32. Ge:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p²

33. As:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p³

34. Se:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁴

35. Br:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁵

36. Kr:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶

37. Rb:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 5s¹

38. Sr:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 5s²

39. Yr:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹ 5s²

40. Zr:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d² 5s²

41. Nb:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d³ 5s²

42.Mo:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d⁵ 5s¹

43. Tc:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d⁵ 5s²

44. Ru:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d⁶ 5s²

45. Rh:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d⁷ 5s²

46. Pd:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶4d⁸ 5s²

47. Ag:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p² 4d¹⁰ 5s¹

48. Cd:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s²

49. In:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p¹

50. Sn:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p²

51. Sb:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p³

52. Te:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁴

53. I:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁵

54. Xe:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶

55. Cs:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 6s¹

56. Ba:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 6s²

57. La:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹ 5s² 5p⁶ 6s²

58. Ce:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f² 5s² 5p⁶ 6s²

59. Pr:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f³ 5s² 5p⁶ 6s²

60. Nd:

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f⁴ 5s² 5p⁶ 6s²

How to write the electron configuration of an ion?

As you know, there are two types of ions: cations and anions. So, first, let’s see how cations are done.

Electron configuration of a cation

When forming cations, electrons are removed from the farthest energy level. So, when you are writing the electron configuration of a cation, all you have to do is subtract the number corresponding to the cation charge from the farthest energy level. So, let’s go ahead with some examples.

11. Na: 1s² 2s² 2p⁶ 3s¹

Na⁺: 1s² 2s² 2p⁶

13. Al: 1s² 2s² 2p⁶ 3s² 3p¹

Al³⁺: 1s² 2s² 2p⁶

20. Ca: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s²

Ca²⁺: 1s² 2s² 2p⁶ 3s² 3p⁶

22. Ti: 1s2² 2s² 2p⁶ 3s² 3p⁶ 3d² 4s²

Ti³⁺: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹

26. Fe: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶ 4s²

There are two common cations of Fe: Fe²⁺ and Fe³⁺.

Fe²⁺: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶

Fe³⁺: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵

29. Cu: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s¹

Like Fe, Cu also has two common cations which are Cu⁺ and Cu²⁺.

Cu⁺: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰

Cu²⁺: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁹

30. Zn: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s²

Zn²⁺: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰

Electron configuration of an anion

When writing the electron configuration of an anion, add the number of electrons equal to the charge to the element’s atomic formula and write as usual. So, here are some examples for you.

1. H: 1s¹

H^–: 1s²

7.N: 1s² 2s² 2p³

N^3-:1s² 2s² 2p⁶

8. O: 1s² 2s² 2p⁴

O^2-: 1s² 2s² 2p⁶

15. P: 1s² 2s² 2p⁶ 3s² 3p³

P^3-: 1s² 2s² 2p⁶ 3s² 3p⁶

16. S: 1s² 2s² 2p⁶ 3s² 3p⁴

S^2-: 1s² 2s² 2p⁶ 3s² 3p⁶

17. Cl: 1s² 2s² 2p⁶ 3s² 3p⁵

Cl^–: 1s² 2s²2p⁶ 3s² 3p⁶

35. Br: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁵

Br^–:1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶

Conclusion

So, I hope that now you can write the electron configuration of any element or ion. If you got any doubt, feel free to ask.