Question

In each of the following sets of elements, indicate which element shows the most active chemical behavior. a. \(\mathbf{B}, \mathbf{A l}, \mathbf{I n}\) b. \(\mathrm{Na}, \mathrm{Al}, \mathrm{S}\) \(\mathrm{c} \cdot \mathrm{B}, \mathrm{C}, \mathrm{F}\)

Short answer

In summary, the elements with the most active chemical behavior in each set are: a. In (Indium) b. Na (Sodium) c. F (Fluorine)

Step-by-step solution

Set a#: B, Al, In

B (Boron) is a metalloid, Al (Aluminum) is a metal and In (Indium) is a metal. Compared to metalloids and non-metals, metals generally have higher chemical reactivity. Both Al and In are in Group 13, but In is located below Al in the periodic table. Elements lower in a group generally have lower ionization energy and higher reactivity. Therefore, in this set, In (Indium) shows the most active chemical behavior.

Set b#: Na, Al, S

Na (Sodium) is an alkali metal, Al (Aluminum) is a metal, and S (Sulfur) is a non-metal. Alkali metals are known for their high reactivity due to their low ionization energy. Metals, in general, have higher chemical reactivity than non-metals. In this set, Na (Sodium) shows the most active chemical behavior.

Set c#: B, C, F

B (Boron) is a metalloid, C (Carbon) is a non-metal, and F (Fluorine) is a halogen. Halogens, being in the second-most right column of the periodic table, have high electronegativity and chemical reactivity. In this set, F (Fluorine) shows the most active chemical behavior.

Key concepts

Periodic Table Trends

The periodic table is not just a tool for organizing elements; it reveals trends in element behavior and properties. As you move from left to right across a period, you'll notice that electron affinity and electronegativity increase. This is because elements on the right side tend to want to gain electrons to fulfill their outer electron shells.
On the other hand, moving down a group in the periodic table demonstrates increasing atomic size. This trend happens because additional electron shells are added, making the outer electrons farther from the nucleus.
With respect to chemical reactivity, elements on the left, particularly alkali metals, are known for their high reactivity. They have only one electron in their outer shell which they can easily lose, making them highly reactive. In contrast, non-metals on the right tend to gain electrons, thus the halogens are notably reactive as well.

• Across a period (left to right): increases in electronegativity and electron affinity.
• Down a group: increases in atomic size and often an increase in reactivity due to additional electron shells.
• Alkali metals are very reactive due to their history of easily losing an electron.
• Halogens are reactive because they readily gain electrons to complete their valence shells.

Ionization Energy

Ionization energy is the energy required to remove an electron from an atom in its gaseous state. It gives a measure of an atom's willingness to part with an electron. This energy varies noticeably across the periodic table.
Generally, ionization energy increases as you move from left to right across a period. This is because electrons are more strongly attracted to the nucleus, making them more difficult to remove. Higher nuclear charge without additional electron shell shielding is responsible for this.
Conversely, as you move down a group, the ionization energy decreases. This is because the outermost electrons are farther from the nucleus and are shielded by inner electron layers, making them easier to remove.

• High ionization energy means an element is less likely to lose electrons easily, which often correlates to less reactivity in metals.
• Lower ionization energy in alkali metals means they readily lose their outer electron, hence they are very reactive.
• In a period, moving left to right, ionization energy generally increases.
• In a group, moving down, ionization energy generally decreases.

Types of Elements

The periodic table categorizes elements into metals, metalloids, and non-metals. Each type exhibits different chemical and physical properties that influence their reactivity and use.
**Metals**, like sodium and aluminum, are typically shiny, conductive, and highly malleable. Most metals, especially alkali metals, have low ionization energies and tend to lose electrons, making them excellent conductors and very reactive.
**Non-metals** include elements like sulfur and fluorine. These elements typically have higher electronegativities and ionization energies compared to metals. Non-metals tend to gain electrons to fill their outer shells, resulting in varying levels of reactivity.
**Metalloids**, such as boron, share properties of both metals and non-metals. Their reactivity can vary considerably depending on the reaction conditions and the specific elements involved. Metalloids serve as a bridge between metals and non-metals.

• Metals: conductive, malleable, tend to lose electrons, especially reactive among alkali metals.
• Non-metals: tend to gain electrons, reactive in different ways, includes gases like fluorine which are highly reactive.
• Metalloids: behave with properties of metals and non-metals, often seen as a balance or transition.