For which of these elements would the first ionization energy of the atom be higher than that of the diatomic molecule?
helium
oxygen
carbon
lithium
Please explain why and thanks
To determine which of these elements would have a higher first ionization energy for the atom compared to the diatomic molecule, we need to consider their electron configurations and the concept of ionization energy.
Ionization energy refers to the amount of energy required to remove an electron from an atom or ion. In general, it is easier to remove an electron from an atom than from a diatomic molecule because an atom has a lower effective nuclear charge.
First, let's analyze the electron configurations of each element:
- Helium (He): Its electron configuration is 1s², which means it has a completely filled 1s orbital, making it highly stable. As a result, helium has a high ionization energy for both the atom and the diatomic molecule.
- Oxygen (O): Its electron configuration is 1s² 2s² 2p⁴. Oxygen has six valence electrons, and removing one electron requires breaking the stability of a half-filled p orbital. However, in the O₂ diatomic molecule, there is a bond formed by sharing electrons between the two oxygen atoms, making it more difficult to remove an electron. Therefore, the first ionization energy of the oxygen atom would be higher than that of the diatomic molecule.
- Carbon (C): Its electron configuration is 1s² 2s² 2p². Carbon has a half-filled p orbital, making it relatively stable. Similar to oxygen, the presence of a covalent bond in the diatomic molecule (C₂) would make it more difficult to remove an electron compared to the carbon atom. Hence, the first ionization energy of the carbon atom would be higher than that of the diatomic molecule.
- Lithium (Li): Its electron configuration is 1s² 2s¹. Lithium has a single valence electron in the 2s orbital. Unlike helium, oxygen, and carbon, there is no diatomic molecule for lithium (Li₂). Therefore, there is no comparison to be made, and the first ionization energy of the lithium atom is not relevant in this context.
In summary, among the given elements, the first ionization energy of the atom would be higher than that of the diatomic molecule for both oxygen (O) and carbon (C).