Question

The bond order of a He2+ ion is:

a. 0

b. 0.5

c. 1

d. 1.5

e. 2

Answer B

Please solve this step by step. Let me know if I am suppose to memorize anything. Why can it be the other answers.

Answer 1

Concepts and reason

The concept used to solve this problem is to determine bond order in the by using MO or molecular orbitals diagram.

Fundamentals

The general molecular orbital is formed as follows:

The sigma (σ) bonding molecular orbitals, the electron probability of both molecular orbitals are centered along the line passing through the two nuclei.

The sigma (σ) bonding molecular orbital

When the parallel p orbital are combined with the positive and negative phases matched, constructive interference occurs, giving a bonding π orbital, electron probability lies above and below the line between the nuclei.

Bonding π orbital

The sigma (σ^*) anti-bonding molecular orbitals, the anti-bonding MO has greater electron probability on either side of nuclei.

The sigma (σ^*) anti-bonding molecular orbitals

When the parallel p orbital have opposite phase the π^* anti-bonding MO are formed.

The π^* anti-bonding MO orbital

The bond order in a molecule is one-half the difference between the number of electron in bonding molecular orbitals and the number in anti-bonding molecular orbitals.

Importance of bond order:

1.Stability of molecules or ions:

If the bond order is positive the molecule or ions will be stable, but if the value of bond order is zero or negative the molecule or ion will be un-stable.

2.Bond dissociation energy:

Bond dissociation energy is directly proportional to the bond order. Hence the more value of bond order; greater will be the bond dissociation energy .

3.Bond length:

Bond order is inversely proportional to bond length. This means that greater the bond order, smaller will be the bond length.

4.Number of bonds:

The value of bond order predicts the number of covalent bonds in the molecules. For example if the value of bond order is 2, thus there are two covalent bonds.

There are two types of ions: positive and negative ions; which are formed when an neutral atom either loses or gains an electron.

Since a negative ion is formed by the addition of one or two electrons to a neutral atom, the resulting anion is larger than its parents.

Similarly a positive ion is formed when an element, mostly a metal loses 1 or more electrons; the resulting cation is smaller than its parents.

The following MOs are occupied in and :

Calculate the bond order of ion as follows:

Ans:

Thus, the bond order in is .