Electron dot structure gives idea about the planer (2D) structure of a molecule. This article will discuss about SeCl4 lewis structure and the method of drawing it.
To draw SeCl4 lewis structure, the atomic symbols of atoms are written,the outer orbit electrons of the atoms are shown by dot symbols. From this we can predict many propeerties like hybridization, shape, polarity etc.
How to draw lewis structure for SECL4
SeCl4 Lewis structure gives idea about outer most orbit electrons of the atoms. These electrons are responsible for characteristic properties in the molecule.
To draw SeCl4 lewis structure, the atomic symbols of atoms are written, that is ‘Se’ for Selenium and ‘Cl’ for Chlorine The outer orbit electrons of an atom are shown by dot symbols around that particular atom of the Selenium tetrachloride molecule.
Selenium is a ‘group 16’ element and Chlorine is a ‘group 17’ element in the Periodic table.
Electronic configuration of Selenium: [Ar] 3d10 4s2 4p4. Electronic configuration of Chlorine: [Ne] 3s2 3p5. So outer most orbit electrons of Selenium atom are six and that of Chlorine atom are seven.
For four Chlorine atoms and one Selenium atom, the total number of the outer orbit electrons are {6 + (7×4)} =34. Hence 17 pairs of electrons participate to form a SeCl4 molecule.
Being the less electronegative atom, Selenium is the central atom in the molecule. Chlorine atoms are around the central atom. Four Chlorine atoms form sigma bonds (single bond) with Selenium atom. Eight electrons (four pairs of electrons) take part in bond formation.
Each Chlorine atom of the SeCl4 molecule has six unshared electrons. Central atom Selenium has one pair of unshared electron over it.
Straight lines are used for showing the bonding electrons of the sigma bond in the molecule.
SECL4 lewis structure shape
SeCl4 lewis structure shape can be found out with the help of VSEPR theory (Valence shell electron pair repulsion theory).
This theory states that the outer most orbit electrons of the atoms are arranged in a way that there is a minimum repulsion between the electrons in the molecule.
This theory assumes that, the unshared electrons (lone pair) cover more space than the bonding electrons. The repulsion between lone pair- bond pair is greater than the repulsion between bond pair- bond pair. Hence if a central atom contains unshared electron pair, the geometry of the molecule disturbed.
Hybridization of central atom Selenium is sp3d in the molecule. For this the geometry of the molecule should be trigonal bipyramidal. But central atom has one unshared pair of electron. For repulsion the molecule has a distorted tetrahedral shape.
SECL4 lewis structure formal charges
The electron dot structure which has ‘zero’ formal charge that is regarded as the stable structure of the molecule among all the possible electron dot structure.
Formal charge of a atom in a molecule = (total number of outer shell electrons – nonbonding electrons – (1/2×bonding electrons))
From the lewis structure of the molecule, we know that outer most orbit electrons of Selenium are six and that of Chlorine are seven. Selenium atom has two unshared electrons whereas each Chlorine atom has six unshared electrons.
Formal charge for the central atom Selenium is = {6- 2- (1/2×8)} = 0.
Formal charge for the each Chlorine atom is = {7- 6- (1/2×2)} = 0.
As the charge on the individual atoms in the molecule is zero, hence the formal charge of the molecule, SeCl4 is also Zero.
SECL4 lewis structure lone pairs
In a molecule lone pair contains such type of electrons which don’t take part in the bonding formation.
In SeCl4 lewis structure, there are 34 outer shell electrons that mean 17 pairs of electrons. Among these electrons only eight electrons make bond between the central atom Selenium and the four chlorine atoms. Remaining all are unshared electrons.
There are thirteen pairs of electrons that not participate in the molecule formation. Among these each Chlorine atom has three pair of that electrons and Selenium has one pair of unshared electrons or lone pair.
SECL4 hybridization
In the concept of hybridization, mixing of atomic orbitals take place. The component orbitals are comparative in energy.
The new hybridized orbital is different in energy with respect to the component orbitals. In the Selenium tetrachloride molecule, only consider the hybridization of the Selenium atom. This helps to determine the geometry of the molecule.
In the unexcited Selenium atom, it has two unpaired electrons in 4p orbital. Beside this it has two pair of electrons in the outer orbit, one is in 4s orbital and another one is in 4p orbital. So it can form two bond pair in this state.
But Selenium has ‘d’ orbital, where paired electrons from 4p orbital can sift and become unpaired one. Now the 4s orbital, three 4p orbital and one 4d orbital mixed up together. This results in the formation of sp3d hybridized orbital.
The hybridized orbital are same in energy. So the bonding overlap of the new orbital with the ligand orbitals becomes better than the unhybridized orbitals.
SECL4 lewis structure resonance
SeCl4 lewis structure may have many forms. The electron dot structures are made by delocalizing of the unshared electrons.
In Selenium tetrachloride molecule, both the Selenium and Chlorine atoms have pair of unshared electron. They can delocalize from the parent atom and form resonating structure. Among these lewis structures, which have the ‘zero’ formal charge that would be the real configuration.
Chlorine is more electronegative than the Selenium atom. So it can bear the negative charge easily. Pi (π) back bonding occurs i.e.4pπ (Se) – 3dπ (Cl) in the molecule.
It means that the unshared electron of Selenium delocalized to the vacant 3d orbital of the Chlorine atom. This results in the formation of the partial pi (π) bonding in the molecule.
As the nonbonding electrons of the Selenium atom involve in the back bonding the repulsion between the bonding electron pair and this unshared electron pair decreases.
SECL4 lewis structure octet rule
Octet rule relates with the electronic stability of the elements in the Periodic table.
All main group elements of the Periodic table like to have eight electrons in the last orbit. This tend to have full filled orbitals is named as Octet rule. Only Hydrogen atom can have highest two electrons in the orbit. This is because it has only ‘K’ orbit.
Selenium has six electrons in the outer orbit. It prefers two more electrons to be like nearest Noble gas Krypton. Chlorine atom has seven electrons in the outer orbit, so it accepts that electron from Selenium atom. In this way both cover eight electrons in the outer shell. This gives the molecule stable structure.
SECL4 polar or nonpolar
Polarity is a physical property of a molecule if the molecule has a net dipole moment generated by polar bonds.
In the Selenium tetrachloride molecule, electronegativity of Selenium (Se) is 2.55 and that of Chlorine is 3.16 on the Pauling scale. For this difference between the electronegativity of the atoms, an unequal charge separation occurs in the molecule. This results a net dipole moment e and SeCl4 becomes polar.
The capacity of strongly pulling the electron cloud of a covalent bond towards the atom is the measurement of electronegativity of that atom. The electronegativity gives a direction of dipole moment. If these direction vectors are not cancelled out each other, a net dipole moment generated.
In the Selenium tetrachloride molecule, Selenium atom has six outer most orbit electrons where Chlorine atom has seven outer shell electrons. SeCl4 molecule has total 34 outer most orbit electrons in the molecule. Among these eight electrons (4 pairs of electron) make bond in the molecule and Selenium has two unshared electrons (one pair of electron).
The geometry of the molecule should be trigonal bipyramidal. From VSEPR theory we know that lone pair- bond pair repulsion is greater than bond pair- bond pair repulsion. For the nonbonding electron pair of the central atom Selenium, the shape of the molecule becomes distorted tetrahedral.
For the distorted shape, the direction of dipole moments for electronegativity difference, can’t neutralized each other. Selenium tetrachloride become a polar molecule
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Hi…I am Triyasha Mondal, pursuing M.Sc in Chemistry. I am an enthusiastic learner. My specialization is in physical chemistry.
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