32 Questions
What is the ionization energy of an atom?
The minimum amount of energy required to remove the outermost electron from an isolated gaseous atom in its ground state.
What is the unit of ionization enthalpy?
kJ mol-1
Is the process of ionization generally endothermic or exothermic?
Endothermic
What is the difference between the first and second ionization enthalpy?
The second ionization enthalpy (I2) is always larger than the first ionization enthalpy (I), because in the second ionization, the electron is removed from an already positive ion.
How is the theoretical ionization energy calculated?
Using the equation I.E = ..., where R∞ is the Rydberg constant, Z* is the effective nuclear charge, n is the principal quantum number, NA is Avogadro’s number, and Eel is electronegativity.
How are ionization energies measured experimentally?
Using photoelectron spectroscopy (PES)
What is the trend of the first ionization energy in the periodic table?
It increases up and to the right in the periodic table.
What explains the substantial increase in ionization energy from hydrogen to helium?
The second proton in the nucleus, which means each electron in the 1s orbital of helium is only slightly shielded by the other.
What is the effect of increasing atomic size on ionization enthalpy?
Ionization enthalpy decreases.
What is the electron configuration of Nitrogen (N)?
1s2 2s22p3
How does an increase in nuclear charge affect ionization enthalpy?
Ionization enthalpy increases.
Why does an electron in a doubly occupied p orbital require less energy to remove?
Because it is repelled by the other electron.
What is the effect of shielding on the nuclear charge experienced by the outermost electron?
Shielding decreases the nuclear charge experienced by the outermost electron.
What is the reason for the decrease in ionization energy from P to S?
The electron configurations, 1s2 2s22p6 3s2 3p3 and 1s2 2s22p6 3s2 3p4, respectively.
What is the order of screening effect among s, p, d, and f orbitals?
s < p < d < f.
Why is the ionization energy for Zn higher than for Ga?
The valence electron in Zn is in a 3d subshell, which is more stable than the 4p level in Ga.
Why does the ionization energy of s electrons decrease in the order s > p > d > f?
S electron cloud has maximum density near the nucleus.
What is the general trend for ionization energy in the periodic table?
It increases up and to the right.
Where are metals located in the periodic table?
To the left of the metal-nonmetal line.
Why does Be have a lower ionization energy than B?
Electrons in p orbitals are slightly higher in energy and further from the nucleus than electrons in s orbitals.
What are the elements that border the staircase called?
Metalloids.
Why does Mg have a higher ionization energy than Al?
Electrons in p orbitals are slightly higher in energy and further from the nucleus than electrons in s orbitals.
Why are half-filled and completely filled subshells more stable than otherwise filled subshells?
They are more stable due to exceptional stability.
Why are metals easily oxidized?
Because they hold their valence electrons loosely.
What is the energy change known as when an electron is added to a neutral gaseous atom in its ground state?
Electron gain enthalpy
Why are electron affinities usually reported as positive numbers despite being a negative process?
For historical reasons
What is the trend of electron affinities in the periodic table?
They generally increase up and to the right
How does the size of an atom affect its electron gain enthalpy?
As size increases, the magnitude of ∆egH decreases
What is the effect of effective nuclear charge on electron gain enthalpy?
As ENC increases, ∆egH increases
Why do elements of group 18 have positive electron gain enthalpies?
Because they have a stable octet structure
What happens to the electron added to an atom as you progress down a column?
It experiences a smaller nuclear attraction due to being in a higher energy level (larger n)
What can explain the exceptions to the general periodic trend of electron affinities?
Electron configurations
Study Notes
Ionization Energy
- Ionization energy is the minimum energy required to remove an outermost electron from an isolated gaseous atom in its ground state.
- The unit of ionization energy is kJ/mol-1, formerly ev and kcal/mol-1.
- It is generally an endothermic process (∆H = +).
- Theoretical ionization energies can be calculated using the equation: I.E = (R∞ * Z*^2) / (n^2 * NΑ), where R∞ is the Rydberg constant, Z* is the effective nuclear charge, n is the principal quantum number, and NΑ is Avogadro's number.
- Experimentally, ionization energies are measured using photoelectron spectroscopy (PES).
Factors Affecting Ionization Energy
- Atomic size: As atomic size increases, the attraction of the nucleus on the outermost electron decreases, and ionization energy decreases.
- Nuclear charge: As nuclear charge increases, ionization energy increases.
- Shielding of outer electrons: Inner electrons neutralize part of the nuclear charge experienced by the outermost electron, leading to a decrease in ionization energy.
- Nature of the orbital: Ionization energy decreases in the order s > p > d > f, as the electron cloud density near the nucleus affects the energy required to remove an electron.
Ionization Energy Exceptions
- Be and B have lower ionization energies due to the electron configuration, where electrons in p orbitals are higher in energy and further from the nucleus than electrons in s orbitals.
- N and O have lower ionization energies due to the removal of an electron from a doubly occupied p orbital, which is repelled by the other electron and requires less energy to remove.
- Zn has a higher ionization energy than Ga due to the removal of an electron from a stable filled 3d subshell in Zn, whereas the removal of an electron from Ga leads to a stable electron configuration.
Electron Affinity (Electron Gain Enthalpy)
- Electron gain enthalpy is the enthalpy change when an electron is added to a neutral gaseous atom in its ground state.
- The energy of this process is known as the electron gain enthalpy, which is usually negative but can be positive for noble gases.
- Electron affinity (E.A.) has the same magnitude but the opposite sign of the electron gain enthalpy.
Factors Affecting Electron Affinity
- Atomic size: As size increases, the magnitude of ∆egH decreases, e.g., down the group 1 and group 17.
- Effective nuclear charge (ENC): As ENC increases, ∆egH increases, e.g., along the second period.
- Progressing down a column, the electron is added to a quantum level farther from the nucleus, resulting in a lower E.A.
Electron Affinity Exceptions
- There are exceptions to the general periodic trend, e.g., N, C, and Ne have lower E.A. than expected due to their electron configurations.
This quiz covers the concept of ionization energy, also known as ionization potential or ionization enthalpy, which is the minimum energy required to remove an outermost electron from a gaseous atom. It involves the enthalpy change and units of measurement.
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