Phosphorus, achemical element with the symbol P and atomic number 15, is an essential elementfor life as it is one of the major components of DNA, RNA, ATP, and phospholipids.The elemental phosphorus exists in two major forms, white phosphorus, and redphosphorus but due to high reactivity, it does not found in a free state on earth.

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It oxidation statesare varies from -3 to +5 (-3, -2,-1, 0, +1, +2, +3, +4, +5) and its electronegativityvalue is 2.19 according to the Pauli scale.

You are here toknow valence electrons of phosphorus atom, aren’t you? Don’t worry along with phosphorusvalence electrons we will explain its valency also. But before that let’s havesome basic ideas about what these two terms are:

Difference BetweenValence Electrons and Valency

Valence electronsare 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 arealways definite, it cannot be varied (more or less) in any condition for aparticular atom and may or may not be equal to its valency.


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

Phosphorus (P)Valence Electrons

There are foursimple steps to find out the valence electrons for phosphorus atom which are:

Step 1: Find theAtomic Number


To find out theatomic number of phosphorus, we can use the periodic table. With the help ofthe periodic table, we can easily see that the atomic number of phosphorus is 15.As its atomic number is 15, it has 15 protons, and for neutral phosphorus, thenumber of protons is always equal to the number of electrons i.e. has 15electrons in its nucleus.

Step 2: WriteElectron Configuration


Electronconfiguration is the arrangement of electrons on the orbitals. The phosphorusatom has a total of 15 electrons so, we have to put 15 electrons in orbitals. Theelectrons 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,

Phosphorus electronconfiguration P (15) =1s22s22p63s23p3(completeconfiguration).

= 3s²3p³(condensed configuration).

Step 3: DetermineValence Shell

As we know, thevalence shell of an atom can be found from the highest number of principlequantum numbers which are expressed in the term of n, and in 3s²3p³, thehighest value of n is 3 so that the valence shell of phosphorus is3s²3p³.

Step 4: FindValence Electrons

The total number ofelectrons present in the valence shell of an atom are called valence electrons,and there are a total of five electrons present in the valence shell of phosphorus(3s²3p³). Thus,phosphorus has five valence electrons.

Valency of Phosphorus(P)

There are manydifferent ways to find out the valency of an atom which reflects the ability ofan atom to bond with other atoms. Valence describes how easily an atom or afree radical can combine with other chemical species. The valency of an atom isdetermined based on the number of electrons lost, gained, or shared withanother atom at the time of bond formation.

An atom is said tobe 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, thevalency is calculated by subtracting from eight and valency will be zero. Atomshaving four outermost electrons possess both positive and negative valency, andatoms having eight outermost electrons, valency will be zero (i.e. noblegases).

Elements like phosphoruscan reach the stable state (nearest inert gas configuration: Ar) by getting 3 electrons.Sothat the valency of phosphorus is 3 (trivalent).

Note: Basically, phosphorushas a stable oxidation state of +3 and +5 in compound formations so that itcan forms both PCl3 and PCl5 in stable states. Do not confuse with +3 or +5,it is just an oxidation number that can vary from compound to compound. But itsvalency is 3 only in any case.

In another sense, aphosphorus atom can form a maximum of three covalent bonds in chemical bonding (Forexample: PH3, PCl3, etc.), and that what valency is, the maximum ability to formbonds with atoms at the time of chemical reactions.

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We can also find the valency of phosphorus withthe help of the periodic table. As phosphorus belongs to group 15 (5A or VA) alongwith nonmetal nitrogen (N), the metalloids arsenic (As) and antimony (Sb), andthe metal bismuth (Bi). These group elements are also called pnictogens. All theseelements have a valency of 3.