Question

Which among the following is an incorrect
statement?
(1) Sigma molecular orbitals are symmetrical around the bond-axis
(2) He2 does not exist
(3) F2 contains ten electrons in bonding molecular orbital
4) C2 contains one sigma and one pi bond
Please answer soon.. With explanation ​

Answer 1

Answer:

(1) sigma molecure or orbitals are symmetrical around the bond- axis

Answer 2

Answer:

The incorrect statement is "C₂ contain one sigma and one pi bond". C₂ contains two pi bonds.

Explanation:

C₂ molecule is formed when two hydrogen atoms combine. The number of electrons in one C atom is 6 electrons. Therefore, the number of electrons in the C₂ molecule is 12. The molecular orbital diagram shows that the degenerate pi bond set of orbitals contains 2 sets of electrons which are paired. Thus, there are two pi bonds formed.

• In the case of diatomic molecules, molecular orbitals are designated as sigma, pi, delta etc. If the molecular orbital is symmetrical about the internuclear axis or bond axis it is called a sigma molecular orbital. If it is not symmetrical about the bond axis it is called a pi molecular orbital.

• He₂ does not exist. This is because the molecular orbital diagram of He₂ contains 2 electrons in the bonding and 2 electrons in the anti-bonding molecular orbital. On calculating the bond order,$Bondorder =\frac{Bonding electron-Antibonding electron}{2}$

       The bond order for He₂ is

       $Bond order = \frac{2-2}{2} = 0$

        The bond order value of zero means that there is no formation of a      bond between two He atoms. Such a molecule is unstable and does not exist.

• Each fluorine atom contains 9 electrons. The molecular orbital diagram for F₂ shows that there are 10 electrons in the bonding molecular orbital and 8 electrons in the anti-bonding molecular orbital. The molecular orbitals obtained by the addition of atomic orbital are called the bonding molecular orbitals. The molecular orbitals obtained by subtraction of the atomic orbitals are called anti-bonding molecular orbitals.