What is the number of the principal energy level in which the valence electrons are found in MG?

The electron configuration of Magnesium can be found using the Aufbau principle.

Aufbau Principle:

• The word ‘Aufbau’ in German means ‘building up’.
• The Aufbau rule simply gives the order of electrons filling in the orbital of an atom in its ground state.
• It states that the orbital with the lowest energy level will be filled first before those with high energy levels. In short, the electrons will be filled in the orbital in order of their increasing energies.
• For example, the 1s orbital will be filled first with electrons before the 2s orbital.

Simply understand that there are commonly four different types of subshells – s, p, d, and, f.

These subshells can hold a maximum number of electrons on the basis of a formula, 2(2l + 1) where ‘l’ is the azimuthal quantum number.

Value of ‘l’ for different subshells.

So, in short, the s subshell can hold a maximum of 2 electrons(1 orbital), the p subshell can hold 6 electrons(3 orbitals), the d subshell can hold 10 electrons(5 orbitals), and the f subshell can hold at most 14 electrons(7 orbitals).

Now, the electron configuration of an atom can be built by filling the electrons in a lower energy subshell first then higher, higher, and higher.

Generally, (n + l) rule is used to predict the energy level of subshells.

n = principle quantum number

l = Azimuthal quantum number

⇒ Lower the value of (n + l) for an subshell, the lower its energy, hence, it will be filled first with electrons.

⇒ For two different subshells having same (n + l) value, then the subshell with lower value of n has lower energy.

So, all these are basics of How filling of electrons will be done in different subshells, obviously, you don’t have so much time for writing electron configuration by using so many rules.

Therefore, we have a diagonal rule for electron filling order in the different subshells using the Aufbau principle.

So, the order in which the orbitals are filled with electrons from lower energy to higher energy is – 1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s < 4f < 5d < 6p < 7s < 5f < 6d < 7p and so on.

Magnesium Electron configuration using the Aufbau Principle

• A Magnesium atom is a neutral atom that has an atomic number of 12 which implies it has a total of 12 electrons.
• As per the Aufbau rule, the electrons will be filled into 1s orbital first then 2s, then 2p…so on.
• Now, for the electron configuration of Magnesium, the first 2 electrons will go in 1s orbital since s subshell can hold a maximum of 2 electrons.
• The next two electrons will go into the 2s orbital, after that, the next 6 electrons will go into the 2p orbital since the p subshell can hold up to 6 electrons.
• Now, we are left with 2 electrons, this will go in a 3s orbital.
• Therefore, the electron configuration of Magnesium will be 1s22s22p63s2.

Magnesium (Mg) Electron Configuration

Check – Electron configuration calculator to count the electron configuration for any atom

Orbital diagram for Magnesium

The orbital diagram simply represents the arrangement of electrons in the different orbitals of an atom, it uses an arrow to represent the electrons, every orbital(one box) contains a maximum of 2 electrons.

There are three rules followed for drawing the orbital diagram for an atom.

(1). Aufbau’s principle:- This rule state that the lower energy orbital will be filled before the higher energy orbital, for example – the 1s orbital will fill before the 2s orbital.

(2). Hund’s rule:- This rule state that each orbital of a given subshell should be filled with one electron each before pairing them. That means “Each orbital gets one electron first, before adding the second electron to the orbital”.

(3). Pauli Exclusion Principle:- This rule state that, no two electrons can occupy the same orbital with the same spin. That means “One must be spin up (↑) and one must be spin down (↓)”.

If you understand the above rules then constructing the orbital diagram or orbital notation for Magnesium is super easy.

Basics of Orbital diagram:-

There are different types of orbitals – s, p, d, and, f. These orbitals contain a number of boxes that can hold a number of electrons. Let’s see.

Each box will hold a maximum of 2 electrons with opposite spin.

• S orbital contains 1 box that can hold a maximum of 2 electrons.
• P orbital contains 3 boxes that can hold a maximum of 6 electrons.
• D orbital contains 5 boxes that can hold a maximum of 10 electrons.
• F orbital contains 7 boxes that can hold a maximum of 14 electrons.

The orbital diagram will also be filled with the same order as described by the Aufbau principle. (1s < 2s < 2p < 3s……and so on.)

Also check – Orbital diagram calculator

What is the Orbital diagram for Magnesium?

We know the electron configuration of Magnesium is 1s22s22p63s2, now for drawing its orbital diagram, we need to show its electrons in form of an arrow in different boxes using Hund’s and Pauli’s exclusion rule.

• The orbital diagram of Magnesium contains 1s orbital, 2s orbital, 2p orbital, and 3s orbital. 1s orbital contains 1 box, 2s orbital also contains 1 box, 2p orbital contains 3 boxes, and 3s orbital contains 1 box.
• Magnesium has a total of 12 electrons and one box can hold up to two electrons.
• Therefore, the first two electrons will go into the 1s orbital, the next two will go into the 2s orbital, and after that, the next six electrons will go into the 2p orbital, since, the 2p orbital has 3 boxes, so, these electrons will be filled using Hund’s rule. (Each box gets one electron first, then start pairing).
• After filling these orbitals, we are still left with 2 electrons, this will go in 3s orbital.

Magnesium Orbital diagram

Electron configuration Vs Orbital diagram for Magnesium

The main difference between the orbital diagram and electron configuration is an orbital diagram shows electrons in form of arrows whereas an electron configuration shows electrons in form of numbers. Also, the orbital diagram shows details on the spin of electrons whereas the electron configuration doesn’t show it.

Both these follow the Aufbau principle (Diagonal rule).

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Electron configuration for Magnesium via Bohr model (Orbit)

Bohr model describes the visual representation of orbiting electrons around the small nucleus. It used different electron shells such as K, L, M, N…so on.

These electron shells hold a specific number of electrons that can be calculated via the 2n2 formula where n represents the shell number.

So, K is the first shell or orbit that can hold up to 2 electrons, L is the 2nd shell which can hold up to 8 electrons, M is the third shell that can hold up to 18 electrons, and N is the fourth shell that can hold up to 32 electrons.

Now, Magnesium has an atomic number of 12 and it contains a total number of 12 electrons. Hence, 2 electrons will go in the first shell(K), 8 electrons will go in the second shell(L), and the remaining two electrons will go in the third shell(M).

Therefore, the electrons per shell for Magnesium are 2, 8, 2, hence, we can say, based on the shell, the electronic configuration of the Magnesium atom is [2, 8, 2].

Also check – How to draw Bohr model of Magnesium atom

Magnesium Valence electrons

Valence electrons are the outermost electrons present in the outermost shell of an atom. They have more energy, hence, they are part of most chemical reactions.

We can find valence electrons of an atom either by knowing its periodic group number or its electron configuration. Both these ways are super easy.

Finding Magnesium Valence electrons through the Group number

For neutral atoms, the valence electrons of an atom will be equal to its main periodic group number. However, for transition metals, the process of finding valence electrons is complicated.

Now, for determining the valence electron for the Magnesium atom, look at the periodic table and find its Group number. The group number can be found from its column on the periodic table.

So, the number of valence electrons in Magnesium is 2. Since it belongs to Group 2 in the Periodic table.

Finding Magnesium Valence electrons through the Electron configuration or Bohr model

We know, the electron configuration of the Magnesium atom is 1s22s22p63s2, and valence electrons are those electrons found in the outer shell of an atom.

This electron configuration of Magnesium shows that the outer shell of Magnesium has just 2 electrons(3s2), hence, the number of valence electrons in the Magnesium atom is 2.

Also, we know, the electron configuration of Magnesium based on the shells is [2, 8, 2], which means, that two electrons are present in the first shell, eight electrons are present in the 2nd shell, and two electrons are present in the third shell or outer shell.

Hence, the electrons found in the 3rd shell of the Magnesium atom are its valence electrons because it is the outermost shell also called the valence shell.

The 3rd shell or outer shell of the Magnesium atom contains only 2 electrons, therefore, the number of valence electrons in the Magnesium atom is 2.

Check – Valence electron calculator to calculate the number of valence electrons for any atom

Electron configuration, Valence electrons, and Orbital diagram of Magnesium in tabular form

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FAQ

The orbital diagram for Magnesium is drawn with 4 orbitals. The orbitals are 1s, 2s, 2p, and 3s. The Magnesium orbital diagram contains 2 electrons in the 1s orbital, 2 electrons in the 2s orbital, the six electrons in the 2p orbital, and the remaining two electrons in the 3s orbital. An orbital diagram for a ground-state electron configuration of the Magnesium atom is shown below-

Properties of Magnesium

• It appears as shiny gray solid and tarnishes slightly when exposed to air.
• Among all alkaline earth metals, it has the lowest boiling and melting point.
• It has a hexagonal close-packed crystal structure.
• It has a boiling point of 1091 °C and a melting point of 650 °C.
• It is paramagnetic in nature.
• It has 1.31 electronegativity according to the Pauling scale.
• Its oxidation state varies from 0 to +2.
• It is highly flammable and can produce a brilliant white light.

Summary

• The electron configuration of Magnesium in terms of the shell or orbit is [2, 8, 2].
• The ground-state electron configuration of the Magnesium (Mg) atom is 1s22s22p63s2. And for the excited state, it is 1s22s22p63s13p1.
• The shorthand electron configuration for Magnesium is [Ne] 3s2.
• The electron configuration for the Magnesium ion (Mg2+) is 1s22s22p6.
• The number of valence electrons available for the Magnesium atom is 2. Magnesium is situated in Group 2nd and has an atomic number of 12.
• The first shell of Magnesium has 2 electrons and the outer shell or valence shell of Magnesium has 2 electrons, hence, the number of valence electrons in the Magnesium atom is 2.
• The orbital diagram for Magnesium is drawn by following three principles – the Aufbau principle, Hund’s principle, and Pauli’s exclusion principle.
• The Magnesium orbital diagram comprises four orbitals. The four orbitals are 1s, 2s, 2p, and 3s.
• The first two electrons will go in the 1s orbital, the next two in the 2s orbital, the next six in the 2p orbital, and the remaining two electrons in the 3s orbital.