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

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

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

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:

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 :

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

element X  

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electrons and atomic orbitals  

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about subatomic particles statement  

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

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.

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explanation: