# Magnesium Electron Configuration – Aufbau & Bohr Model

The electron configuration of magnesium refers to the arrangement of electrons in the magnesium atom’s orbitals. It describes how electrons are distributed among the various atomic orbitals and energy levels, and provides a detailed map of where each electron is likely to be found.

Magnesium is the 12th element in the periodic table and the symbol is ‘Mg’. The atomic number of magnesium is 12, which means its atom has twelve electrons outside the nucleus.

**So, the first two electrons enter the 1s subshell, the next two enter the 2s subshell, the next six enter the 2p subshell and the remaining two enter the 3s subshell. Therefore, the electron configuration of magnesium is 1s ^{2} 2s^{2} 2p^{6} 3s^{2}.**

To understand the mechanism of magnesium electron configuration, you need to understand two basic things. These are orbits and orbitals. Also, you can arrange electrons in those two ways.

In this article, I have discussed all the necessary points to understand the mechanism of magnesium electron configuration. I hope this will be helpful in your study.

## Electron arrangement for Magnesium through orbit

Scientist Niels Bohr was the first to give an idea of the atom’s orbit. He provided a model of the atom in 1913 and provided a complete idea of orbit in that model.

The electrons of the atom revolve around the nucleus in a certain circular path. These circular paths are called orbits (shells or energy levels). These orbits are expressed by n. [n = 1,2,3,4 . . . The serial number of the orbit]

The name of the first orbit is K, L is the second, M is the third, and N is the name of the fourth orbit. The electron holding capacity of each orbit is 2n^{2}.

Shell Number (n) | Shell Name | Electrons Holding Capacity (2n^{2}) |

1 | K | 2 |

2 | L | 8 |

3 | M | 18 |

4 | N | 32 |

### Explanation:

- Let, n = 1 for K orbit. So, the maximum electron holding capacity in the K orbit is 2n
^{2}= 2 × 1^{2}= 2 electrons. - n = 2, for L orbit. The maximum electron holding capacity in the L orbit is 2n
^{2}= 2 × 2^{2}= 8 electrons. - n=3 for M orbit. The maximum electron holding capacity in the M orbit is 2n
^{2}= 2 × 3^{2 }= 18 electrons. - n=4 for N orbit. The maximum electron holding capacity in N orbit is 2n
^{2}= 2 × 4^{2}= 32 electrons.

Therefore, the maximum electron holding capacity in the first shell is two, the second shell is eight and the 3rd shell can have a maximum of eighteen electrons.

The atomic number is the number of electrons in that element. The atomic number of magnesium is 12. That is, the number of electrons in magnesium is twelve. Therefore, the magnesium atom will have two electrons in the first shell, eight in the 2nd shell, and two in the 3rd shell. Hence, the order of the number of electrons in each shell of a magnesium(Mg) atom is 2, 8, 2.

The Bohr atomic model has many limitations. In the Bohr atomic model, the electrons can only be arranged in different shells but the exact position, orbital shape, and spin of the electron cannot be determined.

Also, electrons can be arranged correctly from 1 to 18 elements. The electron arrangement of any element with atomic number greater than 18 cannot be accurately determined by the Bohr atomic model following the 2n^{2} formula. We can overcome all limitations of the Bohr model following the electron configuration through orbital.

## Electron configuration of Magnesium through orbital

Atomic energy shells are subdivided into sub-energy levels. These sub-energy levels are also called orbital. The most probable region of electron rotation around the nucleus is called the orbital.

The sub-energy levels depend on the azimuthal quantum number. It is expressed by ‘l’. The value of ‘l’ is from 0 to (n – 1). The sub-energy levels are known as s, p, d, and f.

Orbit Number | Value of ‘l’ | Number of subshells | Number of orbitals | Subshell name | Electrons holding capacity | Electron configuration |

1 | 0 | 1 | 1 | 1s | 2 | 1s^{2} |

2 | 0 1 | 2 | 1 3 | 2s 2p | 2 6 | 2s^{2} 2p^{6} |

3 | 0 1 2 | 3 | 1 3 5 | 3s 3p 3d | 2 6 10 | 3s^{2} 3p^{6} 3d^{10} |

4 | 0 1 2 3 | 4 | 1 3 5 7 | 4s 4p 4d 4f | 2 6 10 14 | 4s^{2} 4p^{6} 4d^{10} 4f^{14} |

### Explanation:

- If n = 1,

(n – 1) = (1–1) = 0

Therefore, the value of ‘l’ is 0. So, the sub-energy level is 1s. - If n = 2,

(n – 1) = (2–1) = 1.

Therefore, the value of ‘l’ is 0, 1. So, the sub-energy levels are 2s, and 2p. - If n = 3,

(n – 1) = (3–1) = 2.

Therefore, the value of ‘l’ is 0, 1, 2. So, the sub-energy levels are 3s, 3p, and 3d. - If n = 4,

(n – 1) = (4–1) = 3

Therefore, the value of ‘l’ is 0, 1, 2, 3. So, the sub-energy levels are 4s, 4p, 4d, and 4f. - If n = 5,

(n – 1) = (n – 5) = 4.

Therefore, l = 0,1,2,3,4. The number of sub-shells will be 5 but 4s, 4p, 4d, and 4f in these four subshells it is possible to arrange the electrons of all the elements of the periodic table.

Sub-shell name | Name source | Value of ‘l’ | Value of ‘m’(0 to ± l) | Number of orbital (2l+1) | Electrons holding capacity2(2l+1) |

s | Sharp | 0 | 0 | 1 | 2 |

p | Principal | 1 | −1, 0, +1 | 3 | 6 |

d | Diffuse | 2 | −2, −1, 0, +1, +2 | 5 | 10 |

f | Fundamental | 3 | −3, −2, −1, 0, +1, +2, +3 | 7 | 14 |

The orbital number of the s-subshell is one, three in the p-subshell, five in the d-subshell, and seven in the f-subshell. Each orbital can have a maximum of two electrons.

The sub-energy level ‘s’ can hold a maximum of two electrons, ‘p’ can hold a maximum of six electrons, ‘d’ can hold a maximum of ten electrons, and ‘f’ can hold a maximum of fourteen electrons.

Aufbau is a German word, which means building up. The main proponents of this principle are scientists Niels Bohr and Pauli. The Aufbau method is to do electron configuration through the sub-energy level.

The Aufbau principle is that the electrons present in the atom will first complete the lowest energy orbital and then gradually continue to complete the higher energy orbital.

The energy of an orbital is calculated from the value of the principal quantum number ‘n’ and the azimuthal quantum number ‘l’. The orbital for which the value of (n + l) is lower is the low energy orbital and the electron will enter that orbital first.

Orbital | Orbit (n) | Azimuthal quantum number (l) | Orbital energy (n + l) |

3d | 3 | 2 | 5 |

4s | 4 | 0 | 4 |

Here, the energy of 4s orbital is less than that of 3d. So, the electron will enter the 4s orbital first and enter the 3d orbital when the 4s orbital is full.

Following the Aufbau principle, the sequence of entry of electrons into orbitals is 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p.

**The first two electrons of magnesium enter the 1s subshell. As you already know the s-subshell can hold a maximum of two electrons. Therefore, the next two electrons enter the 2s subshell. Also, you know the p-subshell can hold a maximum of six electrons. So, the next six electrons enter the 2p subshell and the remaining two enter the 3s-subshell. Therefore, the complete electron configuration of magnesium will be 1s ^{2} 2s^{2} 2p^{6} 3s^{2}.**

Note:The unabbreviated electron configuration of magnesium is [Ne] 3s^{2}. When writing an electron configuration, you have to write serially.

## Magnesium ion(Mg^{2+}) Electron configuration

The ground state electron configuration of magnesium is 1s^{2} 2s^{2} 2p^{6} 3s^{2}. After the electron configuration, the last shell of the magnesium atom has two electrons. Therefore, the valency and valence electrons of magnesium are 2.

The elements that have 1, 2, or 3 electrons in the last shell donate the electrons in the last shell during bond formation. Magnesium donates the electron of the last shell to form bonds and turns into a magnesium ion(Mg^{+2}).

The elements that form bonds by donating electrons are called cations. That is, magnesium is a cation element.

Mg – 2e^{–} → Mg^{2+}

The electron configuration of magnesium ion(Mg^{+2}) is 1s^{2} 2s^{2} 2p^{6}. This electron configuration shows that magnesium ion(Mg^{+2}) has acquired the electron configuration of neon and it achieves an octave full stable electron configuration.

## FAQs

### How do you write the complete electron configuration for magnesium?

The complete electron configuration for magnesium is 1s

^{2}2s^{2}2p^{6}3s^{2}.### What is the electron configuration for mg2+?

The electron configuration of magnesium ion(Mg

^{+2}) is 1s^{2}2s^{2}2p^{6}. This electron configuration shows that magnesium ion(Mg^{+2}) has acquired the electron configuration of neon and it achieves an octave full stable electron configuration.### What is the valence electron configuration for the magnesium atom?

The valence electron configuration for the magnesium atom is [Ne] 3s

^{2}.### What is the complete ground state electron configuration for the magnesium atom?

The complete ground state electron configuration for the magnesium atom is 1s

^{2}2s^{2}2p^{6}3s^{2}.### How many filled s orbitals does magnesium have?

Magnesium (Mg) has three filled s orbital. The s orbitals can hold a maximum of 2 electrons, and the electron configuration of magnesium is 1s

^{2}2s^{2}2p^{6}3s^{2}. This means that the 1s orbital is filled with 2 electrons, while the 2s and 3s orbital are also filled with 2 electrons. Therefore, magnesium has three filled s orbital.### What is the abbreviated electron configuration for magnesium?

The abbreviated electron configuration for magnesium is [Ne] 3s

^{2}. The noble gas neon (Ne) has the electron configuration 1s^{2}2s^{2}2p^{6}, which represents the filled inner energy levels. By using the noble gas notation, we can replace this inner electron configuration of neon with the symbol [Ne].### How many electron shells does magnesium have?

Magnesium has 3 electron shells. The electron configuration of magnesium is 1s

^{2}2s^{2}2p^{6}3s^{2}. From this configuration, we can see that there are electrons present in the first, second, and third energy levels (shells). Therefore, magnesium has a total of 3 electron shells.### How many electrons are in the outer orbit of magnesium?

Magnesium (Mg) has 2 electrons in its outer orbit. The outer orbit refers to the outermost energy level, which is the third energy level (designated as the 3s orbital) in the electron configuration of magnesium. In this case, there are 2 electrons in the 3s orbital, which are the valence electrons.

### How many electrons are in the 3s sublevel for magnesium?

The 3s sublevel of magnesium (Mg) contains 2 electrons.

### How many electrons are in the n = 2 shell of a magnesium atom?

The second energy level can hold a maximum of 8 electrons. The electron configuration of magnesium is 1s

^{2}2s^{2}2p^{6}3s^{2}. From this configuration, we can see that there are a total of 8 electrons in the n = 2 shell. This includes the 2 electrons in the 2s sublevel and the 6 electrons in the 2p sublevel. Therefore, the n = 2 shell of a magnesium atom contains 8 electrons.### How many electrons are in the n = 3 shell of a magnesium ion (Mg

^{2+})?The n = 3 shell of the Mg

^{2+}ion does not contain any electrons. When magnesium loses two electrons to form the Mg^{2+}ion, it achieves a stable, noble gas-like configuration similar to neon (Ne). Therefore, the Mg^{2+}ion has the electron configuration of [Ne], representing a filled n = 2 shell.### What is the symbol for magnesium ion?

The symbol for the magnesium ion with a 2+ charge is Mg

^{2+}. The 2+ indicates that the magnesium ion has lost two electrons, resulting in a 2+ charge.