Question

Place the clements in each set in order of decreasing atomic radius. a. \(\mathrm{Al}, \mathrm{S} \mathrm{i}, \mathrm{Mg}\) b. \(\mathrm{Cl}, \mathrm{I}, \mathrm{Br}\) c. \(\mathrm{Sr}, \mathrm{Sb}, \mathrm{I}\) d. \(\mathrm{P}, \mathrm{Si}\), \(\mathrm{Na}\)

Short answer

a: Mg, Al, Si; b: I, Br, Cl; c: Sr, Sb, I; d: Na, Si, P.

Step-by-step solution

- Understand Atomic Radius Trends

Atomic radius increases down a group in the periodic table and decreases across a period from left to right.

- Determine the Group and Period for Each Element in Set (a)

Al (Aluminum) and Si (Silicon) are in the same period (Period 3), while Mg (Magnesium) is also in Period 3. Order in decreasing atomic radius: Mg, Al, Si.

- Apply Trends for Set (b)

Cl (Chlorine), Br (Bromine), and I (Iodine) all belong to Group 17 (Halogens). Order in decreasing atomic radius: I, Br, Cl.

- Analyze Elements in Set (c)

Sr (Strontium) is in Group 2, Sb (Antimony) is in Group 15, and I (Iodine) is in Group 17. Sr has the largest radius being in Period 5. Next, Sb is in Period 5, followed by I in Period 5. Order in decreasing atomic radius: Sr, Sb, I.

- Arrange the Elements in Set (d)

P (Phosphorus) and Si (Silicon) are in Period 3, and Na (Sodium) is also in Period 3. Order in decreasing atomic radius: Na, Si, P.

Key concepts

periodic table

The periodic table is a fundamental tool in chemistry. It organizes all known elements based on their atomic number, electron configurations, and recurring chemical properties.
Each row in the table is called a period, and each column is called a group. Elements in the same group have similar properties because they have the same number of valence electrons.
The periodic table helps predict the properties of elements and how they might react with others.

atomic radius

Atomic radius refers to the size of an atom. It's generally defined as the distance from the nucleus to the outermost electron shell.
The atomic radius can vary depending on the atom's environment, but there are clear trends across the periodic table. As you move down a group, the atomic radius increases.
This is because each successive element has an additional electron shell. Meanwhile, moving from left to right across a period, the atomic radius decreases.
This happens because the electrons are added to the same shell while the number of protons in the nucleus increases, pulling the electron shell closer to the nucleus.

group trends

Understanding group trends is crucial for predicting chemical behavior. In the periodic table, elements in the same group exhibit similar properties.
The atomic radius increases as you move down a group. This is because each element down a group has an additional electron shell, making the atom larger.
Additionally, the shielding effect increases down the group, which weakens the attraction between the nucleus and the valence electrons. This makes the outermost shell further from the nucleus.

period trends

Period trends describe how properties of elements change as you move across a period from left to right. One significant trend is the decrease in atomic radius.
Across a period, electrons are added to the same principal energy level, but protons are also being added to the nucleus. This increases the positive charge in the nucleus, which pulls the electrons closer, decreasing the atomic radius.
These trends are key to understanding the chemical reactivity and the formation of ions and bonds.