How Many Valence Electrons Does Magnesium (Mg) Have? [Valency of Magnesium]

Magnesium, a chemical element with the symbol Mg and atomic number 12, is shiny grey white solid appearance element with the lowest melting and boiling points among all the alkaline earth metals.

Magnesium has a great biological role. The important interaction between phosphate and magnesium ions makes magnesium a very essential element to the nucleic acid of all cells. Also, it is used as nutrition in diet, metabolism, detection in serum and plasma, therapy, etc.

You are here to know valence electrons of a magnesium atom, aren’t you? Don’t worry along with magnesium valence electrons we will explain its valency also. But before that let’s have some basic ideas about what these two terms are:

Difference Between Valence Electrons and Valency

Valence electrons are the total number of electrons present in the outermost shell of an atom (i.e. in outermost orbital). The valence electrons for a neutral atom are always definite, it cannot be varied (more or less) in any condition for a particular atom and may or may not be equal to its valency.

Valency is defined as the total number of electrons an atom can lose, gain, or share at the time of bond formation to get a stable electronic configuration i.e. to complete an octet. The valency of an atom can be variable in different compounds or chemical reactions due to the different bonding circumstances. Most of the time valency varies/changes due to change in oxidation and reduction states.

Magnesium (Mg) Valence Electrons

There are four simple steps to find out the valence electrons for magnesium atom which are:

Step 1: Find the Atomic Number

To find out the atomic number of magnesium, we can use the periodic table. With the help of the periodic table, we can easily see that the atomic number of magnesium is 12. As its atomic number is 12, it has 12 protons, and for neutral magnesium, the number of protons is always equal to the number of electrons i.e. has 12 electrons in its nucleus.

Step 2: Write Electron Configuration

Electron configuration is the arrangement of electrons on the orbitals. The magnesium atom has a total of 12 electrons so, we have to put 12 electrons in orbitals. The electrons will be placed in different orbitals according to the energy level: [1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f]. Now,

Magnesium electron configuration Mg (12) = [Ne] 3s²(complete configuration).

= 1s²2s²2p⁶3s²(condensed configuration).

Step 3: Determine Valence Shell

As we know, the valence shell of an atom can be found from the highest number of principle quantum numbers which are expressed in the term of n, and in [Ne]3s², the highest value of n is 3 so that the valence shell of magnesium is 3s².

Step 4: Find Valence Electrons

The total number of electrons present in the valence shell of an atom are called valence electrons, and there are a total of two electrons present in the valence shell of magnesium (3s²). Thus, magnesium has two valence electrons.

Valency of Magnesium (Mg)

There are many different ways to find out the valency of an atom which reflects the ability of an atom to bond with other atoms. Valence describes how easily an atom or a free radical can combine with other chemical species. The valency of an atom is determined based on the number of electrons lost, gained, or shared with another atom at the time of bond formation.

An atom is said to be stable when its outermost shells have eight electrons (except H & He). If the total number of electrons in outermost shells is between one to four, the atom has positive valency and if electrons are between four to eight, the valency is calculated by subtracting from eight and valency will be zero. Atoms having four outermost electrons possess both positive and negative valency, and atoms having eight outermost electrons, valency will be zero (i.e. noble gases).

Elements like magnesium can reach the stable state (nearest inert gas configuration: Ne) by losing two electrons. So that the valency of magnesium is 2.

Note: Usually, magnesium has a stable oxidation state of +2 most of the time but it may differ in some compounds. Do not confuse with +2 or something else (+1, +3, +4, etc.) with a positive or negative sign, it is just an oxidation number that can vary from compound to compound. But its valency is always 2 in any case.  

In another sense, a magnesium atom can form a maximum of two covalent bonds in a chemical bonding (For example: MgO, MgCl2, MgSO4, etc.), and that what valency is, the maximum ability to form bonds with atoms at the time of chemical bonding.

We can also find the valency of magnesium with the help of the periodic table. As magnesium belongs to group 2A (or IIA) along with beryllium (Be), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). These group elements are also called alkaline earth metals. All these elements have valency two.