i. Draw the molecular orbital energy diagram for Be_(2) (5 marks) Calculate the bond order of Be_(2) (2 marks)

To draw the molecular orbital energy diagram for $Be_{2}$, we need to consider the atomic orbitals of the beryllium atoms and how they combine to form molecular orbitals.<br /><br />1. **Atomic orbitals**: Beryllium has two electrons in the 1s orbital and two in the 2s orbital. For $Be_{2}$, we only need to consider the 2s orbitals.<br /><br />2. **Combination of atomic orbitals**: The 2s orbitals of the two beryllium atoms combine to form molecular orbitals. The bonding orbital is formed by the constructive interference of the two 2s orbitals, while the antibonding orbital is formed by their destructive interference.<br /><br />3. **Energy levels**: The energy levels of the molecular orbitals depend on the distance between the two beryllium atoms. In $Be_{2}$, the bonding orbital is lower in energy than the antibonding orbital.<br /><br />The molecular orbital energy diagram for $Be_{2}$ can be represented as follows:<br /><br />```<br /> Energy<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br /> |<br />The molecular orbital energy diagram for $Be_{2}$ is shown above.<br /><br />To calculate the bond order of $Be_{2}$, we can use the formula:<br /><br />Bond order = (Number of bonding electrons - Number of antibonding electrons) / 2<br /><br />In $Be_{2}$, there are two bonding electrons in the bonding orbital and two antibonding electrons in the antibonding orbital. Therefore, the bond order is:<br /><br />Bond order = (2 - 2) / 2 = 0<br /><br />The bond order of $Be_{2}$ is 0.