Yes, the electron configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 4d¹⁰ 4p⁵ is valid. It corresponds to the element iodine (I), which is a chemical element in the periodic table.

1. Electron Configuration Overview

The electron configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 4d¹⁰ 4p⁵ describes the arrangement of electrons in the electron shells (energy levels) around the nucleus of an atom.

Explanation of the Notation:

• 1s²: Two electrons in the 1st energy level (n=1) in the s orbital.
• 2s²: Two electrons in the 2nd energy level (n=2) in the s orbital.
• 2p⁶: Six electrons in the 2nd energy level (n=2) in the p orbital.
• 3s²: Two electrons in the 3rd energy level (n=3) in the s orbital.
• 3p⁶: Six electrons in the 3rd energy level (n=3) in the p orbital.
• 4s²: Two electrons in the 4th energy level (n=4) in the s orbital.
• 4d¹⁰: Ten electrons in the 4th energy level (n=4) in the d orbital.
• 4p⁵: Five electrons in the 4th energy level (n=4) in the p orbital.

2. Atomic Number and Element

This configuration represents the element iodine (I), which has an atomic number of 53. The atomic number refers to the number of protons in the nucleus of the atom, and it also indicates the number of electrons in a neutral atom.

• The total number of electrons described by the electron configuration is:
  • 1s² → 2 electrons
  • 2s² → 2 electrons
  • 2p⁶ → 6 electrons
  • 3s² → 2 electrons
  • 3p⁶ → 6 electrons
  • 4s² → 2 electrons
  • 4d¹⁰ → 10 electrons
  • 4p⁵ → 5 electrons

  Total electrons = 2 + 2 + 6 + 2 + 6 + 2 + 10 + 5 = 53 electrons.

This matches the atomic number of iodine (I), which is 53, confirming that the configuration is valid for iodine.

3. The Periodic Table Location

• Iodine is a halogen (Group 17) in the period 5 of the periodic table.
• The electron configuration for iodine reflects its position as a halogen, which typically has a 7 valence electrons (the 5 electrons in the 4p orbital plus the 2 electrons in the 4s orbital). Halogens are known for being highly reactive and having one electron short of a full outer shell, which drives their reactivity.

4. Electron Shells and Sublevels

• 1st shell (n=1): Can hold a maximum of 2 electrons (1s²).
• 2nd shell (n=2): Can hold a maximum of 8 electrons (2s² 2p⁶).
• 3rd shell (n=3): Can hold a maximum of 18 electrons (3s² 3p⁶).
• 4th shell (n=4): Can hold a maximum of 32 electrons. In this case, iodine fills up to 4p⁵ with 5 electrons in the 4p orbital after filling the 4s² and 4d¹⁰ orbitals.

5. Hund’s Rule and the Aufbau Principle

• The electron configuration follows the Aufbau principle, where electrons fill orbitals starting from the lowest energy level first and progressing to higher energy levels.
• The 4s orbital fills before the 3d orbital, and the 3p orbital fills before the 4d orbital. This is consistent with the order in which orbitals are filled based on their energy levels.
• According to Hund’s Rule, electrons will occupy degenerate orbitals (orbitals with the same energy) singly before pairing up. In the case of iodine, the 4p orbitals are filled with 5 electrons, which corresponds to the halogen’s valency of 1, as it needs to gain 1 electron to complete its outer shell and become stable.

6. Chemical Properties

• Iodine (I) is a non-metal and typically forms I⁻ ions by gaining 1 electron to fill its outer shell, achieving the stable electron configuration of a noble gas.
• Iodine is also highly reactive as a halogen, and it can form various compounds, including salts like sodium iodide (NaI), when it reacts with metals.

7. Electron Configuration Comparison with Other Elements

• The electron configuration for iodine is similar to that of other halogens. For example:
  • Fluorine (F) has the electron configuration 1s² 2s² 2p⁵ (atomic number 9).
  • Chlorine (Cl) has the electron configuration 1s² 2s² 2p⁶ 3s² 3p⁵ (atomic number 17).
  • Bromine (Br) has the electron configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁵ (atomic number 35).
  • Astatine (At) has the electron configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁵ (atomic number 85).

As you can see, iodine fits into the periodic trend for halogens, with its outermost electrons in the 4p orbital and the configuration ending in 4p⁵.

Conclusion

The electron configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 4d¹⁰ 4p⁵ is valid and represents the element iodine (I). It reflects the atom’s distribution of electrons across its energy levels and sublevels, following the rules of electron configuration and consistent with iodine’s position on the periodic table.