The first ionization energy refers to the energy required to remove the outermost electron from an atom. In the given data, we see a trend in the ionization energies of alkali metals: they decrease as you move down the group in the periodic table. This is due to the increasing distance of the outer electron from the nucleus and the shielding effect of inner electrons.
Analyzing the Trend
From the values provided:
- Lithium: 520 kJ/mol
- Sodium: 496 kJ/mol
- Rubidium: 403 kJ/mol
- Cesium: 376 kJ/mol
As we move from lithium to cesium, the ionization energy decreases. Potassium (K) is located between sodium (Na) and rubidium (Rb) in the periodic table.
Estimating Potassium's Ionization Energy
Given that sodium has an ionization energy of 496 kJ/mol and rubidium has 403 kJ/mol, we can estimate potassium's first ionization energy to be slightly lower than sodium's but higher than rubidium's. This suggests a value around 450 kJ/mol.
Choosing the Closest Option
Looking at the provided options:
- A. 536 kJ/mol
- B. 504 kJ/mol
- C. 419 kJ/mol
- D. 391 kJ/mol
- E. 358 kJ/mol
The closest value to our estimate of potassium's ionization energy is C. 419 kJ/mol.
