q4 What element has the greatest first ionization energy?
Li
Na
K
Rb
Cs
To determine which element has the greatest first ionization energy, we need to understand what ionization energy is and how it varies across the periodic table.
Ionization energy refers to the amount of energy required to remove an electron from a neutral atom and convert it into a positive ion. The first ionization energy specifically refers to the energy required to remove the first electron from an atom.
First ionization energy generally increases across a period (from left to right) on the periodic table and decreases down a group (from top to bottom). This trend is primarily due to the increasing nuclear charge (number of protons) and the distance between the nucleus and the outermost electrons.
Looking at the options provided - Li (lithium), Na (sodium), K (potassium), Rb (rubidium), and Cs (cesium) - we can determine which element has the greatest first ionization energy based on their positions on the periodic table:
- Li is the first element in Group 1 (alkali metals) and has the lowest atomic number among the options given.
- Na is the second element in Group 1, with a slightly higher atomic number than Li.
- K is the third element in Group 1, with a higher atomic number than Na.
- Rb is the fourth element in Group 1, with a higher atomic number than K.
- Cs is the fifth and final element in Group 1, with the highest atomic number among the options.
Since first ionization energy generally increases across a period, we can conclude that cesium (Cs) has the greatest first ionization energy among the given elements.