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Ch.10 - Chemical Bonding I: The Lewis Model
Chapter 10, Problem 41

Use Lewis symbols to determine the formula for the compound that forms between each pair of elements. a. Mg and S b. Sr and Br c. K and Se d. Al and S

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Identify the valence electrons for each element using their group number on the periodic table. For example, Mg is in Group 2 and thus has 2 valence electrons, while S is in Group 16 and has 6 valence electrons.
Determine the total number of electrons each element needs to achieve a stable octet (8 electrons in the outer shell). For instance, Mg needs 6 more electrons to complete its octet, and S needs 2 more electrons.
Decide how the elements can share or transfer electrons to achieve stable octets. For example, Mg can lose 2 electrons to form Mg2+, and S can gain 2 electrons to form S2-.
Combine the ions in a ratio that balances the total positive and negative charges to form a neutral compound. For Mg2+ and S2-, the ratio is 1:1, resulting in the formula MgS.
Repeat the above steps for each pair of elements: Sr and Br, K and Se, Al and S, to determine the formulas SrBr2, K2Se, and Al2S3 respectively, based on their electron transfers and the charges of the resulting ions.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Lewis Symbols

Lewis symbols, or Lewis dot structures, represent the valence electrons of an atom as dots around the element's symbol. This visual representation helps in understanding how atoms bond with each other by either sharing or transferring electrons. In the context of ionic and covalent bonding, Lewis symbols are essential for predicting the formation of compounds between different elements.
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Ionic and Covalent Bonds

Ionic bonds form when one atom donates electrons to another, resulting in the creation of charged ions that attract each other. In contrast, covalent bonds involve the sharing of electrons between atoms. Understanding the nature of the bond formed between elements, such as metals and nonmetals, is crucial for determining the correct formula of the resulting compound.
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Periodic Table Trends

The periodic table organizes elements based on their atomic number and properties, revealing trends in electronegativity, ionization energy, and atomic size. These trends help predict how elements will interact with each other, particularly in terms of electron transfer or sharing. Recognizing these trends is vital for accurately determining the formulas of compounds formed between different pairs of elements.
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