Problem 55 - Chemistry: The Central Science

Question

(a) Does metallic character increase, decrease, or remain unchanged as one goes from left to right across a row of the periodic table? (b) Does metallic character increase, decrease, or remain unchanged as one goes down a column of the periodic table? (c) Are the periodic trends in (a) and (b) the same as or different from those for first ionization energy?

Step-by-Step Solution

Answer

(a) Metallic character decreases as one goes from left to right across a row of the periodic table, due to the increase in effective nuclear charge experienced by the valence electrons. (b) Metallic character increases as one goes down a column of the periodic table, due to the increase in atomic size and electron shielding. (c) The periodic trends for metallic character are opposite those for first ionization energy, meaning they are inversely related.

Step 1: Define Metallic Character

Metallic character refers to an element's ability to lose its electrons and form a positive ion or cation. Elements displaying a high metallic character tend to donate electrons more readily, allowing them to have stronger electrical conductivity and metallic properties. In the periodic table, metallic character is found to generally increase down a group and decrease across a period.

Step 2: Metallic Character Trend across a Period (Left to Right)

Generally, the metallic character decreases as we move from left to right across a period in the periodic table. This is due to the increase in the effective nuclear charge experienced by the valence or outer shell electrons. As we move from left to right in a period, the number of protons increases, and the electrons experience a stronger attraction to the nucleus. This increased attraction makes it more challenging for the atom to lose electrons, hence decreasing the metallic character. Answer (a): Metallic character decreases as one goes from left to right across a row of the periodic table.

Step 3: Metallic Character Trend down a Group (Column)

As we move down a group in the periodic table, the metallic character tends to increase. This is due to the increase in atomic size and electron shielding. Since electron shielding increases as we go down the group due to the addition of electron shells, the effective nuclear charge experienced by the outer electrons decreases. This decreased attraction to the nucleus allows the outer electrons to be more easily lost, resulting in increased metallic character. Answer (b): Metallic character increases as one goes down a column of the periodic table.

Step 4: Compare Trends of Metallic Character with First Ionization Energy

The first ionization energy is the energy required to remove an electron from a neutral atom in its gaseous state. In general, first ionization energy increases from left to right across a period and decreases as we go down a group. This is due to the same factors that affect the metallic character: effective nuclear charge and atomic size. When comparing the trends of metallic character and first ionization energy, it can be seen that they are inversely related. This means that when metallic character increases, the first ionization energy tends to decrease, and vice versa. Answer (c): The periodic trends for metallic character are opposite those for first ionization energy.