Question

According to general trends in the periodic table, predict which element in each of the following pairs has greater metallic character: (a) \(\mathrm{K}\) or \(\mathrm{Ca}\) (b) \(\mathrm{Mg}\) or \(\mathrm{Al}\) (c) Fe or Cu (d) S or Ar

Short answer

(a) K, (b) Mg, (c) Fe, (d) S.

Step-by-step solution

Understanding Metallic Character

Metallic character refers to how easily an element can lose electrons and form positive ions. Metals are typically more likely to lose electrons than nonmetals.

Periodic Table Trend: Metallic Character

As a general trend, metallic character increases as you move down a group and decreases as you move across a period from left to right on the periodic table.

Comparing K and Ca

Both potassium ((K)) and calcium ((Ca)) are in the same period, with potassium to the left of calcium. Since metallic character decreases as you move to the right across a period, (K)) has a greater metallic character than (Ca).

Comparing Mg and Al

Magnesium ((Mg)) and aluminum ((Al)) are in the same period with magnesium to the left of aluminum. Therefore, (Mg)) has a greater metallic character than (Al).

Comparing Fe and Cu

Iron ((Fe)) and copper ((Cu)) are in the same period, with iron to the left of copper. Thus, (Fe)) has a greater metallic character than (Cu).

Comparing S and Ar

Sulfur ((S)) is a nonmetal, and argon ((Ar)) is a noble gas, located far to the right on the periodic table. Nonmetals have lower metallic character. Argon, being a noble gas, exhibits very low metallic character, hence (S)) has slightly greater metallic character than (Ar).

Key concepts

Periodic Table Trends

The periodic table is a powerful tool in chemistry that helps us understand various properties of elements, including their metallic character. As you move down a group (a vertical column) in the periodic table, the metallic character of elements generally increases. This happens because the outer electrons are further from the nucleus and more easily lost. In contrast, when moving across a period (a horizontal row) from left to right, the metallic character decreases. This trend occurs because the effective nuclear charge increases, making it harder for elements to lose electrons. Understanding these trends helps us predict the behavior of elements in chemical reactions.

Electron Loss

The concept of electron loss is crucial when discussing metallic character. Metals tend to lose electrons easily to achieve a stable electronic configuration, often forming positive ions, also known as cations. This tendency is a defining feature of metals. For example, potassium (K) readily loses one electron to form a K⁺ ion. This ease of electron loss is directly linked to the position of an element in the periodic table and influences its reactivity and ability to conduct electricity. Nonmetals, on the other hand, tend to gain electrons rather than lose them, resulting in lower metallic character.

Metals and Nonmetals

Literally dividing the periodic table, metals and nonmetals have distinct characteristics. Metals, found on the left side of the periodic table, are typically shiny, good conductors of heat and electricity, and are malleable. They exhibit a high tendency to lose electrons, which is why they possess metallic character. Nonmetals, situated on the right side, display varied properties but generally have higher electronegativity and do not easily lose electrons. They are often brittle in solid form and are poor conductors. Metals and nonmetals react differently based on their tendency to lose or gain electrons. Thus, knowing if an element is a metal or nonmetal helps us understand its behavior in reactions.

Element Comparison

When comparing elements, understanding their position on the periodic table and their metallic character is essential. Let's consider the pairs from the exercise:

• Potassium (K) vs. Calcium (Ca): Both are in the same period. Potassium is to the left of calcium, thus has greater metallic character.
• Magnesium (Mg) vs. Aluminum (Al): Magnesium, being further to the left, has greater metallic character than aluminum in the same period.
• Iron (Fe) vs. Copper (Cu): Iron is to the left and has greater metallic character than copper.
• Sulfur (S) vs. Argon (Ar): Though both are nonmetals, sulfur has a slightly greater metallic character compared to argon, a noble gas, which exhibits hardly any metallic character.

These comparisons showcase how the periodic table's structure helps us predict relative properties such as metallic character effectively.