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\begin{tabular}{|c|c|c|}
\hline
Element & \begin{tabular}{c}
Atomic \\
Radius
\end{tabular} & \begin{tabular}{c}
First \\
Ionization \\
Energy
\end{tabular} \\
\hline
Calcium & 194 pm & [tex]$590 kJ / mol$[/tex] \\
\hline
Potassium & - & - \\
\hline
\end{tabular}

1. Based on periodic trends and the data in the table above, which of the following are the most probable values of the atomic radius and the first ionization energy for potassium, respectively?

A. [tex]$242 pm , 633 kJ / mol$[/tex]

B. [tex]$242 pm , 419 kJ / mol$[/tex]

C. [tex]$120 pm , 633 kJ / mol$[/tex]

D. [tex]$120 pm , 419 kJ / mol$[/tex]



Answer :

GinnyAnswer
Let's solve this question by analyzing the periodic trends and comparing the elements in the given table.

Step 1: Understanding Periodic Trends

1. Atomic Radius:
- Within a group (vertical column) on the periodic table, the atomic radius increases as we move down the group.
- Within a period (horizontal row), the atomic radius decreases as we move from left to right across the period.

2. Ionization Energy:
- Within a group, the ionization energy decreases as we move down the group.
- Within a period, the ionization energy increases as we move from left to right across the period.

Step 2: Position of Elements

- Calcium (Ca) is in Group 2 and Period 4.
- Potassium (K) is in Group 1 and Period 4.
- Thus, Potassium is directly to the left of Calcium and is below Calcium within the same period.

Step 3: Applying Periodic Trends

- Since Potassium (K) is directly to the left of Calcium (Ca) in the periodic table, Potassium will have:
- A larger atomic radius than Calcium.
- A lower ionization energy than Calcium.

Given data for Calcium:
- Atomic radius of Calcium = 194 pm
- First ionization energy of Calcium = 590 kJ/mol

Step 4: Analyzing the Given Options

Let's analyze each option in the context of the periodic trends:

- Option A: 242 pm, 633 kJ/mol
- Atomic radius is larger than Calcium (correct).
- Ionization energy is higher than Calcium (incorrect, should be lower).

- Option B: 242 pm, 419 kJ/mol
- Atomic radius is larger than Calcium (correct).
- Ionization energy is lower than Calcium (correct).

- Option C: 120 pm, 633 kJ/mol
- Atomic radius is smaller than Calcium (incorrect).
- Ionization energy is higher than Calcium (incorrect, should be lower).

- Option D: 120 pm, 419 kJ/mol
- Atomic radius is smaller than Calcium (incorrect).
- Ionization energy is lower than Calcium (correct, but atomic radius is incorrect).

Conclusion:
Based on the periodic trends and the given data, the most probable values for the atomic radius and the first ionization energy for Potassium are given in Option B:
- Atomic radius = 242 pm
- Ionization energy = 419 kJ/mol

Thus, the answer is:
(B) 242 pm, 419 kJ/mol

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