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Which electron configuration represents the electrons of an atom in an excited state?
(1) 2–8–1 (3) 2–8–17–6(2) 2–8–6 (4) 2–8–18–5



Answer :

Dejanras

Answer is: (3) 2–8–17–6.

1) This is ground state of sodum atom.

Electron configuration of sodium atom: ₁₁Na 1s² 2s² 2p⁶ 3s¹.  

Atomic number of sodium is 11, it means that it has 11 protons and 11 electrons, so atom of sodium is neutral.  

2) This is ground state of sulfur atom.

Sulfur electron configuration: ₁₆S 1s²2s²2p⁶3s²3p⁴.


Sulfur has six valence electrons (3s²3p⁴), in 3s orbital, two electrons are paired, in 3p orbital, two electrons are paired and two are unpaired.

4) This is ground state of arsenic atom.

Electron configuration of arsenic atom:

₃₃As 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p³.

ardni313

Electron configuration represents an excited state : (3) 2–8–17–6

Further explanation

In an atom there are levels of energy in the shell and sub shell

This energy level is expressed in the form of electron configurations.

Writing electron configurations starts from the lowest to the highest sub-shell energy level. There are 4 sub-shells in the shell of an atom, namely s, p, d and f. The maximum number of electrons for each sub shell is

  • s: 2 electrons
  • p: 6 electrons
  • d: 10 electrons and
  • f: 14 electrons

Charging electrons in the sub shell uses the following sequence:

1s², 2s², 2p⁶, 3s², 3p⁶, 4s², 3d¹⁰, 4p⁶, 5s², 4d¹⁰, 5p⁶, 6s², etc.

Determination of electron configurations based on principles:

  • 1. Aufbau: Electrons occupy orbitals of the lowest energy level
  • 2 Hund: electrons fill orbitals with the same energy level
  • 3. Pauli: no electrons have the same 4 quantum numbers

According to Niels Bohr, electrons surround the nucleus of an atom on a path called the electron shell. Each shell has an energy level. The further from the core, the higher the energy level

Maximum electrons of shells :

  • K shell: 2 electrons
  • L shell: 8 electrons
  • M shell: 18 electrons
  • N shell: 32 electrons
  • O shell: 50 electrons
  • P shell: 72 electrons

The maximum number of electrons in each shell can be formulated = 2n² (n = shell number)

Electrons can move the shell up or down by releasing energy or absorbing energy

Excited electrons show higher electron transfer to the shell by absorbing energy

So it can be concluded that there are 2 conditions :

Ground state is the state of electrons filling skins with the lowest energy levels.

Excited state is the state of electrons which occupy a higher energy level

The state of excited electrons can be seen from the presence of electrons which do not fill the skin completely but fill the skin afterwards

From the electron configuration , option 3 shows the excitation of one electron in the M shell towards the N shell, which should have a configuration in the ground state:

2–8–18–5

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Keywords: electron configurations, the shell of atoms, excited state