Question

Which of the following elements is the least chemically reactive? (A) fluorine, based on its seven valence electrons (B) neon, based on its Group 8 status (C) lithium, based on its one valence electron (D) sulfur, based on its six valence electrons

Short answer

The least chemically reactive element among the given options is (B) neon, based on its Group 8 status and stable electron configuration, which does not readily form compounds.

Step-by-step solution

Recall the meaning of valence electrons and group status

Valence electrons are the electrons in the outermost shell of an atom, and these play a significant role in determining the atom's chemical reactivity. Group status refers to the position of an element in the periodic table, and elements in the same group tend to have similar properties due to having the same number of valence electrons.

Compare the electron configurations of the given elements

We need to compare the given elements based on their valence electrons and group status to see which one has the most stable electron configuration. (A) Fluorine is in Group 17 of the periodic table and has seven valence electrons. It is highly reactive because it can easily gain one electron to achieve the stable noble gas configuration. (B) Neon is in Group 18 (also known as Group 8) of the periodic table and has a full set of eight valence electrons. It has a stable electron configuration, which is similar to the noble gas configuration. Therefore, it is not reactive and does not readily form compounds. (C) Lithium is in Group 1 of the periodic table and has one valence electron. This means it can easily lose one electron to achieve the stable helium configuration. Thus, it is highly reactive. (D) Sulfur is in Group 16 of the periodic table and has six valence electrons, meaning it can gain two electrons to achieve the stable noble gas configuration. However, this means that it is still reactive and tends to form compounds.

Determine the least chemically reactive element

Based on their electron configurations and group status, the least chemically reactive element among the given options is neon (B), as it already has a stable electron configuration and does not readily form compounds.

Key concepts

Valence Electrons

Understanding valence electrons is crucial to grasping the fundamental behaviors of atoms in chemical reactions. Simply put, valence electrons are the electrons situated in the outermost electron shell of an atom. These electrons play a pivotal role in bond formation, as they participate in chemical reactions by either being gained, lost, or shared to achieve stability in the form of a full valence shell, imitating the electron configuration of noble gases.

For instance, in our exercise, fluorine, with seven valence electrons, seeks to complete its octet by gaining a single electron, resulting in a propensity for high reactivity. Conversely, neon, which already boasts a full set of valence electrons (eight), does not seek additional electrons and therefore remains largely unreactive. Hence, identifying the number of valence electrons provides insight into an element's reactivity.

Periodic Table Groups

The periodic table is organized into columns known as groups which are pivotal in predicting the chemical behavior of elements. Elements within the same group share the same number of valence electrons, granting them similar reactivity patterns. For example, Group 1 elements (alkali metals) have a single valence electron and are highly reactive as they tend to lose this electron to achieve the electron configuration of the nearest noble gas.

In the exercise provided, neon is grouped in Group 18, the noble gases, which are renowned for their lack of reactivity due to a full valence shell. This characteristic of noble gases directly influences their position as the least reactive elements on the periodic table.

Chemical Reactivity

Chemical reactivity is a measure of how readily an element can combine with others. This trait is largely dictated by an element's desire to reach a state of maximum stability, with noble gases setting the standard due to their complete valence electron shells.

Honing in on the given exercise, it is evident that most elements attempt to attain stability by emulating the electron configuration of noble gases. Fluorine (Group 17) yearns to gain an electron, lithium (Group 1) aims to lose one, and sulfur (Group 16) seeks two additional electrons, highlighting their reactive nature. Conversely, neon is inert, as it is already in a low-energy, stable state. Understanding this concept will significantly aid students in predicting the reactivity of elements.

Electron Configuration

Electron configuration describes the distribution of electrons in an atom across different energy levels and subshells. This distribution governs an atom's reactivity and its chemical properties. Atoms strive for the most stable configuration, which often means mimicking the configuration of the nearest noble gas—either through gaining, losing, or sharing electrons.

Applying this to our exercise, fluorine, lithium, and sulfur are seeking stability, with each requiring a different electron exchange to reach the ideal configuration. In stark contrast, neon's electron configuration is naturally stable. It mirrors that of a noble gas, with no further adjustments being necessary for stability, rendering it the least reactive of the options provided. Grasping these concepts about electron configuration allows for a better understanding of the periodic trends in reactivity and the underlying reasons for the chemical behavior of elements.