1. For which of these elements would the first ionization energy of the atom be higher than that of the diatomic molecule?
a. boron
b. helium
c. oxygen
d. lithium
lithium
To determine which element would have a higher first ionization energy for the atom compared to the diatomic molecule, let's examine the electron configuration and the trend in ionization energy.
a. Boron (B): The electron configuration of boron is 1s² 2s² 2p¹. The diatomic molecule of boron, B₂, would have a molecular orbital composed of the overlapping atomic orbitals of two boron atoms. The first ionization energy of an atom is generally higher than that of a diatomic molecule because breaking the bond requires more energy. Therefore, the first ionization energy of the atom of boron is higher than that of the diatomic molecule.
b. Helium (He): The electron configuration of helium is 1s². Since helium is a noble gas, it is already stable with a full valence shell. Therefore, the first ionization energy of helium would be higher for the atom compared to the diatomic molecule.
c. Oxygen (O): The electron configuration of oxygen is 1s² 2s² 2p⁴. The diatomic molecule of oxygen, O₂, would have a molecular orbital composed of the overlapping atomic orbitals of two oxygen atoms. Similar to boron, the first ionization energy of the atom of oxygen is higher than that of the diatomic molecule.
d. Lithium (Li): The electron configuration of lithium is 1s² 2s¹. The diatomic molecule of lithium, Li₂, would have a molecular orbital composed of the overlapping atomic orbitals of two lithium atoms. The first ionization energy of the atom of lithium is higher than that of the diatomic molecule.
In summary, the elements for which the first ionization energy of the atom would be higher than that of the diatomic molecule are:
- Boron (B)
- Oxygen (O)
To determine the element for which the first ionization energy of the atom is higher than that of the diatomic molecule among the given options (boron, helium, oxygen, and lithium), we need to understand the concept of ionization energy.
Ionization energy refers to the amount of energy required to remove an electron from an atom or ion in its gaseous state. This energy is typically measured in electron volts (eV) or kilojoules per mole (kJ/mol). When comparing the first ionization energies of atoms versus diatomic molecules, we need to consider the electron configuration and atomic structure of each element.
Now, let's evaluate each of the given options:
a. Boron (B): The atomic number of boron is 5, and its electron configuration is 1s²2s²2p¹. In diatomic boron (B₂), the molecule is formed by bonding two boron atoms, resulting in the sharing of electrons. The removal of an electron requires breaking the bond. Since the bond strengthens the attraction on the outermost electron, the ionization energy of the diatomic molecule (B₂) would be higher when compared to the ionization energy of the atom (B). Therefore, the first ionization energy of the atom (B) is lower than that of the diatomic molecule (B₂).
b. Helium (He): The atomic number of helium is 2, and its electron configuration is 1s². Helium does not readily form diatomic molecules, as it is a noble gas with a stable electron configuration. Therefore, for helium, the ionization energy of the atom (He) would be higher than that of any hypothetical diatomic molecule. Thus, the first ionization energy of the atom (He) is higher than that of any diatomic molecule.
c. Oxygen (O): The atomic number of oxygen is 8, and its electron configuration is 1s²2s²2p⁴. Oxygen readily forms diatomic molecules (O₂). In the diatomic molecule, the electron-electron repulsion is reduced, making it easier to remove an electron compared to the atom (O). Consequently, the first ionization energy of the atom (O) is higher than that of the diatomic molecule (O₂).
d. Lithium (Li): The atomic number of lithium is 3, and its electron configuration is 1s²2s¹. In diatomic lithium (Li₂), the molecule is formed by bonding two lithium atoms. As in the case of boron, the bond in the diatomic molecule strengthens the electron's attraction, resulting in a higher ionization energy compared to the atom (Li). Hence, the first ionization energy of the atom (Li) is lower than that of the diatomic molecule (Li₂).
Therefore, among the given options, the element for which the first ionization energy of the atom is higher than that of the diatomic molecule is b. helium (He).