Question

question 3. the figure below illustrates the ionization of different elements according to their positions in the periodic table.

part a. what is the definition of ionization energy?

part b. what is the trend in ionization energy as you go across the periodic table from left to right?

part c. what is the trend in ionization energy as you go down the periodic table from top to bottom?

Explanation:

Part A:

Ionization energy is defined as the minimum amount of energy required to remove the most loosely bound electron (the valence electron) from an isolated gaseous atom or ion in its ground state to form a gaseous ion with a positive charge (a cation). For example, for a sodium atom (\( \text{Na} \)), the ionization energy is the energy needed to remove its outermost electron to form \( \text{Na}^+ \) ion: \( \text{Na}(g)
ightarrow \text{Na}^+(g) + e^- \).

Part B:

As you move across a period (from left to right) in the periodic table, the ionization energy generally increases. This is because, across a period, the number of protons in the nucleus (nuclear charge) increases while the electrons are added to the same principal energy level (shell). The increasing nuclear charge pulls the electrons more strongly towards the nucleus, making the outermost electrons more tightly bound. As a result, more energy is required to remove an electron. For example, in Period 2, lithium (Li) has a lower ionization energy than beryllium (Be), which is lower than boron (B), and so on, up to neon (Ne), which has a relatively high ionization energy.

Part C:

As you move down a group (from top to bottom) in the periodic table, the ionization energy generally decreases. This is because, down a group, the principal quantum number (\( n \)) of the outermost electrons increases, meaning the electrons are located in shells that are farther from the nucleus. The increased distance from the nucleus, along with the shielding effect of inner electron shells (which reduces the effective nuclear charge experienced by the outermost electrons), makes the outermost electrons less tightly bound. Thus, less energy is required to remove an electron. For example, in Group 1, lithium (Li) has a higher ionization energy than sodium (Na), which is higher than potassium (K), and so on.

Answer:

Part A:

The minimum energy required to remove a valence electron from an isolated gaseous atom/ion in its ground state to form a gaseous cation (e.g., \( \text{X}(g)
ightarrow \text{X}^+(g) + e^- \)).

Part B:

Ionization energy generally increases across a period from left to right.

Part C:

Ionization energy generally decreases down a group from top to bottom.