Bromine, a chemicalelement with the symbol Br and atomic number 35, is a very reactive gas so thatdoes not occur in free states but exists as halide salts or table salts. At standardtemperature and pressure, it is found as a liquid like mercury.
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You are here toknow valence electrons of bromine atom, aren’t you? Don’t worry along with brominevalence 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 orchemical reactions due to the different bonding circumstances. Most of the timevalency varies/changes due to change in oxidation and reduction states.
Bromine (Br)Valence Electrons
There are four simplesteps to find out the valence electrons for bromine atom which are:
Step 1: Find theAtomic Number
To find out theatomic number of bromine, we can use the periodic table. With the help of theperiodic table, we can easily see that the atomic number of bromine is 35. Asits atomic number is 35, it has 35 protons, and for neutral bromine, the numberof protons is always equal to the number of electrons i.e. has 35 electrons inits nucleus.
Step 2: WriteElectron Configuration
Electronconfiguration is the arrangement of electrons on the orbitals. The bromine atomhas a total of 35 electrons so, we have to put 35 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,
Bromine electronconfiguration Br (35) =1s22s22p63s23p63d104s24p5(completeconfiguration).
Step 3: DetermineValence Shell
As we know, thevalence shell of an atom can be found from the highest number of principlequantum numbers are expressed in the term of n, and in
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 seven electrons present in the valence shell of bromine(4s² 3d¹⁰ 4p⁵). Thus,bromine has seven valence electrons.
Valency of Bromine(Br)
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 brominecan reach the stable state (nearest inert gas configuration: Ar) by getting oneelectron.So that the valency of bromine is 1.
Mathematically, theelectronic configuration of bromine is 2, 8, 18, 7. And as we know, ifelectrons in the outermost shell exceed from 4, it should be subtracted from 8. So,
ElectronConfiguration of bromine (Br) = 2, 8, 18, 7
We can see theoutermost shell of bromine has 7 electrons so, have to subtract it from 8.
8 – 7 = 1
That’s why valencyof bromine is 1.
Note: In general, brominehas a stable oxidation state of -1 most of the time but it can differ insome compounds with values 0 (Br2), +1 (NaBrO), +3 (NaBrO2), +4 (BrO3), +5 (NaBrO3),+7 (NaBrO4). Do not confuse with -1 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 1 in any case.
In another sense, abromine atom can form a maximum of one covalent bond in a chemical bonding (For example:HBr, CH3Br, CaBr2, etc.), and that what valency is, the maximum ability to formbonds with atoms at the time of chemical bonding.
We can also findthe valency of bromine with the help of the periodic table. As bromine belongsto group 17 (17A or VIIA) along with fluorine (F), chlorine (Cl), iodine (I), andastatine (At). These group elements are also called halogens. All these elementshave valency one.