For the molecule given below give the following bonding treatment: a) Lews struc
ID: 925262 • Letter: F
Question
For the molecule given below give the following bonding treatment: a) Lews structure, b) resonance structures, if ony, c) formal charges of oil atoms in one of the resonance structures if there is more than one, d) VSEPR designation (L1 A Xx). e) a sketch of the molecule showing position of substituent (terminal) atoms and lone pairs on the central atom, f) abatement of the molecular geometry, g) polarity of the overall molecule, h) hybridization on the central atom, and i) a picture of the sigma and pi structure (where appropriate)Explanation / Answer
As with configuration [ Ar ]3d^10 4s^2, 4 p^3 , is bonded to three Cl atoms with single bonds ( ie. a sharing of one electron each from As & separate chlorine atoms.) This results into a lone pair of electron over As atom .Hence,
Formal charge on central atom = [ Total number of valence electrons on the central atom ] - [ total no. of nonbonding ( lone pair ) of electrons - 1/2 [ total no. of bonding or shared electrons ]
--------------------------------------------- = 5 - 2 - 1/2 ( 6 ) = 0
Shape or molecular geometry - Trigonal Pyramidal
One AsCl3 molecule will have a total of 26 valence electrons - ie. 5 from As atom and 7 each from three separate Cl atoms. Since As atom is bonded to three separate Cl atoms through single bonds each chlorine atom would possess three lone pair of electrons. Thus arsenic atom with its own lone pair of electron is surrounded by 4 regions of electron density which means that the steric number is equal to 4., giving a molecular geometry as AX3 E1 representing a Trigonal Pyramidal shape.
Hybridization - sp^3
We have 5 (As ) + 3 x 7 (Cl ) = 26 sp valence electrons in the structure. Thus there must be a lone pair of electron on arsenic atom . So there are 4 electron pairs on As & so 4 hybrid orbitals are needed causing sp^3 hybridization on the molecule.
Polarity - Polar
Because of the lone pair of electrons over As and a more electronegative chlorine atom forming three separate bonds , the molecule should be polar.The two chlorine atoms are at an angle of 180o while the third Cl atom is at right angle to them , causing net polar charecter in the molecule. Of coursee the lone pair of electron on As atom accounts for the molecular shape - trigoanol pyramidal.