Second ionization energy, which is strongly connected to atomic number, electronegativity, and ionic charge, plays a crucial role in various chemical processes. It represents the energy required to remove an electron from an ion that has already lost one electron. This concept finds applications in understanding both atomic and chemical bonding properties as well as the reactions involving charged species in different chemical systems.
What is Second Ionization Energy?
The second ionization energy refers to the energy required to remove an electron from a once-ionized atom, resulting in the formation of a doubly charged cation. It is expressed in electronvolts (eV) or kilojoules per mole (kJ/mol).
Definition
- The energy needed to remove a second electron from a neutral atom.
- Represented as IE2 or I2.
- Measured in electronvolts (eV) or kilojoules per mole (kJ/mol).
Factors Affecting Second Ionization Energy
- Nuclear Charge: The higher the nuclear charge, the greater the attraction between the nucleus and electrons, resulting in higher ionization energy.
- Electronic Configuration: The stability of the electron configuration before and after ionization affects the ionization energy.
- Size of Atom: Larger atoms have more electron shells, leading to greater distance between the nucleus and outermost electrons, resulting in lower ionization energy.
- Shielding Effect: Inner electrons shield the outermost electrons from the nucleus, reducing the attraction and lowering ionization energy.
Factors that Do Not Affect Second Ionization Energy
- Type of removed electron (1s, 2s, etc.)
- Nature of the cation formed
Periodic Trends
- Across a period (left to right): Generally increases due to increasing nuclear charge.
- Down a group (top to bottom): Generally decreases due to increased atomic size and shielding effect.
Table of Second Ionization Energies
| Element | Symbol | First Ionization Energy (eV) | Second Ionization Energy (eV) |
|---|---|---|---|
| Hydrogen | H | 13.60 | 54.4 |
| Helium | He | 24.59 | 54.4 |
| Lithium | Li | 5.39 | 72.5 |
| Beryllium | Be | 9.32 | 18.21 |
| Boron | B | 8.30 | 24.96 |
| Carbon | C | 11.26 | 24.38 |
| Nitrogen | N | 14.53 | 29.60 |
| Oxygen | O | 13.61 | 35.12 |
| Fluorine | F | 17.42 | 34.97 |
| Neon | Ne | 21.56 | 40.96 |
Question 1: What is second ionization energy?
Answer:
– Second ionization energy is the energy required to remove an electron from an atom or ion that already has one electron removed.
– It is the energy needed to promote an electron from the state of an ion with a +1 charge to the state of an ion with a +2 charge.
Question 2: How does second ionization energy vary across elements?
Answer:
– Second ionization energy generally increases across a period from left to right.
– This is because the effective nuclear charge experienced by the electron increases as more protons are added to the nucleus.
– Second ionization energy also generally decreases down a group.
– This is because the electron being removed is further from the nucleus and experiences less attraction to it.
Question 3: What factors affect the second ionization energy of an element?
Answer:
– The atomic number of the element: The more protons in the nucleus, the higher the second ionization energy.
– The size of the atom: The larger the atom, the lower the second ionization energy.
– The electronic configuration of the atom: The presence of electrons in orbitals with higher n values reduces the second ionization energy.
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