Ionization energy of an element is:

Options

A. Equal in magnitude but opposite in sig to the electron gain enthalpy of the cation of the element
B. Same as electron affinity of the element
C. Enegy required to remove one valence electron from an isolated gseous atom in its ground state
D. Equal in magnitude but opposite in sign to t no gain enthalpy of the anion of the element

Answer

**Step-by-Step Solution:**

1. **Understanding Ionization Energy**: Ionization energy is defined as the amount of energy required to remove an electron from an isolated gaseous atom or ion. It is a measure of how strongly an atom holds onto its electrons.

2. **Factors Affecting Ionization Energy**:
- **Atomic Size**: As the atomic size increases, the ionization energy generally decreases. This is because the outermost electrons are farther from the nucleus and are less strongly attracted to it.
- **Nuclear Charge**: A higher nuclear charge (more protons in the nucleus) generally increases ionization energy, as the increased positive charge attracts the electrons more strongly.
- **Electron Shielding**: Inner shell electrons can shield outer electrons from the full effect of the nuclear charge, reducing ionization energy.
- **Electron Configuration**: Atoms with a stable electron configuration (like noble gases) have higher ionization energies because they are less likely to lose electrons.

3. **Trends in the Periodic Table**:
- **Across a Period**: Ionization energy increases across a period from left to right due to increasing nuclear charge and decreasing atomic size.
- **Down a Group**: Ionization energy decreases down a group due to increasing atomic size and increased electron shielding.

4. **Conclusion**: The ionization energy of an element can be determined by considering its position in the periodic table and the factors affecting it.

**Final Answer**: Ionization energy of an element is the energy required to remove an electron from an isolated gaseous atom.

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