Problem 52 - Chemistry: An Atoms-Focused Approach

Question

Draw Lewis symbols for the most stable ions formed by lithium, magnesium, aluminum, and fluorine.

Step-by-Step Solution

Answer

Question: Draw the Lewis symbols for the most stable ions formed by lithium (Li), magnesium (Mg), aluminum (Al), and fluorine (F). Answer: The Lewis symbols for the most stable ions are: Li^+: Li Mg^2+: Mg Al^3+: Al F^-: F:

Step 1: Determine the atomic numbers and electron configurations

Using the periodic table, we can find the atomic numbers for each element: Lithium (Li) - atomic number: 3 Magnesium (Mg) - atomic number: 12 Aluminum (Al) - atomic number: 13 Fluorine (F) - atomic number: 9 The electron configurations are determined from the atomic number as follows: Lithium (Li): 1s^2 2s^1 Magnesium (Mg): 1s^2 2s^2 2p^6 3s^2 Aluminum (Al): 1s^2 2s^2 2p^6 3s^2 3p^1 Fluorine (F): 1s^2 2s^2 2p^5

Step 2: Determine the most stable ions

The most stable ions for each element can be determined by the octet rule, where an atom is most stable when its valence electron shell is filled or has eight electrons: Lithium (Li): loses 1 electron -> Li^+ (1s^2) Magnesium (Mg): loses 2 electrons -> Mg^2+ (1s^2 2s^2 2p^6) Aluminum (Al): loses 3 electrons -> Al^3+ (1s^2 2s^2 2p^6) Fluorine (F): gains 1 electron -> F^- (1s^2 2s^2 2p^6)

Step 3: Draw Lewis symbols for the most stable ions

To draw Lewis symbols, place the element's symbol in the center and surround it by dots representing the valence electrons in its most stable ion configuration: Lithium (Li^+): Li Magnesium (Mg^2+): Mg Aluminum (Al^3+): Al Fluorine (F^-): F: : None of the cations (Li^+, Mg^2+, and Al^3+) have any valence electrons in their most stable ion configurations, so no dots are surrounding them. The anion F^- has eight valence electrons (achieved by gaining 1 electron), and it has four pairs surrounding it in the Lewis symbol.

Key Concepts

Electrons

Electrons are tiny subatomic particles that orbit around the nucleus of an atom. They carry a negative charge and are key players in determining how atoms interact with each other. Electrons are organized in electron shells or energy levels around the nucleus. The closest shell is filled first, followed by the outer shells.

• The distribution of electrons in these shells defines the electron configuration of an atom.
• Electron configuration helps in predicting the kind of chemical bonds an atom will form with others.

For example, the electron configurations of lithium, magnesium, aluminum, and fluorine show how many electrons each element has and which energy levels they occupy. This is essential for understanding their stability and tendency to form ions.

Ionic Compounds

Ionic compounds are formed when atoms transfer electrons to achieve greater stability. This transfer usually occurs between metals and nonmetals.

• Metals tend to lose electrons, becoming positively charged ions called cations.
• Nonmetals tend to gain electrons, forming negatively charged ions known as anions.

When these opposite charges attract, they create a strong ionic bond, resulting in a stable compound. For example, when lithium (a metal) loses an electron, it forms a Li⁺ ion, while fluorine (a nonmetal) gains an electron to become F^-. This electron exchange helps each element achieve a stable electron configuration, akin to noble gases.

Octet Rule

The octet rule is a guiding concept in chemistry, stating that atoms aim to have a full set of eight electrons in their outermost shell, similar to noble gases. This configuration usually grants the atom increased stability.

• Atoms will lose, gain, or share electrons to satisfy the octet rule.
• It's particularly applicable for elements in the second period of the periodic table.

For example, lithium (Li) loses one electron to achieve a full outer shell like helium, while fluorine (F) gains one electron to mirror the electronic structure of neon. The rule is useful in predicting the common ion forms and behaviors of elements, aiding in the understanding of chemical reactions and the formation of stable ions, as seen in the step-by-step exercise solution.