Identify the neutral element represented by this excited-state electron configuration, then write the ground-state electron configuration for that element.
Excited State: 1s2 2s2 2p2 3s1
Element Symbol: ?
Ground State: ?

1s² 2s² 2p³

Nitrogen

Explanation:

Excited state configuration: 1s² 2s² 2p² 3s¹

Unknown:

Ground state configuration = ?

Element symbol = ?

Solution:

Let us start by understanding what a ground state configuration entails:

A ground state configuration shows the lowest allowed energy levels of an atom. The excited state denotes when electrons have moved to higher energy levels away from their ground state.

The superscript in the configuration depicts the number of electrons in each of the sublevels.

We can use this number to identify the atom we are dealing with:

 Total number of electrons = 2 + 2 + 2 + 1 = 7 electrons

The element with 7 electrons on the periodic table is Nitrogen.

Now, the ground state configuration:

In writing the electronic configuration of an atom, certain rules must be complied with.

Aufbau's principle states that the sublevels with lower energies are filled up before those with higher energies. The order of filling is:

        1s 2s 2p 3s 3p 4s etc

To fill the s-orbital = 2 electrons

                p-orbital = 6 electrons

The outermost shell electrons are usually the ones excited.

  Now, the 3s¹ shell is an excited one taking 1 electron from the second energy level;

 The ground state configuration is 1s² 2s² 2p³

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