Problem 7
Question
The atomic number of sulfur is \(16 .\) Sulfur combines with hydrogen by covalent bonding to form a compound, hydrogen sulfide. Based on the number of valence electrons in a sulfur atom, predict the molecular formula of the compound. \begin{equation} \begin{array} { l l } { \text { (A) } \mathrm { HS } } & { \text { (C) } \mathrm { H } _ { 2 } \mathrm { S } } \\ { \text { (B) } \mathrm { HS } _ { 2 } } & { \text { (D) } \mathrm { H } _ { 4 } \mathrm { S } } \end{array} \end{equation}
Step-by-Step Solution
Verified Answer
The molecular formula is \( \text{H}_2 \text{S} \).
1Step 1: Determine Sulfur's Valence Electrons
Identify the number of valence electrons in a sulfur (S) atom. The atomic number of sulfur is 16, indicating it has 6 valence electrons.
2Step 2: Understand Covalent Bond Formation
In covalent bonding, atoms share electrons to achieve a full outer electron shell. Sulfur needs 2 more electrons to complete its outer shell, achieving a stable octet configuration.
3Step 3: Predict the Bonding Requirement
Hydrogen (H) has 1 valence electron and needs 1 more to fill its shell. Therefore, each hydrogen atom will share one electron with sulfur.
4Step 4: Identify the Molecular Formula
Since sulfur needs 2 additional electrons, it will form 2 covalent bonds with 2 hydrogen atoms. This means the molecular formula will be \( \text {H}_2 \text{S} \).
5Step 5: Conclusion
The correct molecular formula for the compound formed by sulfur and hydrogen based on the given options is \( \text {H}_2 \text{S} \).
Key Concepts
Atomic Number of SulfurCovalent BondingValence Electrons
Atomic Number of Sulfur
The atomic number of an element is crucial as it tells us the number of protons in its nucleus. For sulfur, this number is 16. This means a sulfur atom has 16 protons. Since atoms are electrically neutral overall, sulfur also has 16 electrons. These electrons are arranged in different shells or energy levels around the nucleus.
The distribution of electrons in sulfur is 2 in the first shell, 8 in the second shell, and 6 in the third shell. The electrons in the outermost shell, which in this case are 6, are called valence electrons.
The distribution of electrons in sulfur is 2 in the first shell, 8 in the second shell, and 6 in the third shell. The electrons in the outermost shell, which in this case are 6, are called valence electrons.
Covalent Bonding
Covalent bonding is a type of chemical bond where atoms share pairs of electrons. This typically occurs between nonmetals. Atoms form covalent bonds to achieve stability, which usually means having a full outer shell of electrons.
For sulfur (which has 6 valence electrons), it needs 2 more electrons to complete its outer shell and achieve a stable configuration. Hydrogen, having just 1 valence electron, needs one more to fill its shell. When sulfur bonds with hydrogen, each hydrogen atom shares one of its electrons with sulfur, and sulfur shares one of its own electrons with each hydrogen. Thus, the sulfur atom completes its outer shell by sharing two electrons, one with each of two hydrogen atoms.
This sharing results in the formation of a molecule, hydrogen sulfide (H₂S), where sulfur forms two covalent bonds with two hydrogen atoms.
For sulfur (which has 6 valence electrons), it needs 2 more electrons to complete its outer shell and achieve a stable configuration. Hydrogen, having just 1 valence electron, needs one more to fill its shell. When sulfur bonds with hydrogen, each hydrogen atom shares one of its electrons with sulfur, and sulfur shares one of its own electrons with each hydrogen. Thus, the sulfur atom completes its outer shell by sharing two electrons, one with each of two hydrogen atoms.
This sharing results in the formation of a molecule, hydrogen sulfide (H₂S), where sulfur forms two covalent bonds with two hydrogen atoms.
Valence Electrons
Valence electrons are the electrons in the outermost shell of an atom. They are important because they are involved in chemical bonding. In the case of sulfur, which has six electrons in its outer shell, these are its valence electrons.
The number of valence electrons determines how an atom will bond with other atoms. Sulfur's six valence electrons mean it needs two more electrons to achieve a full outer shell, totaling eight electrons. This is often referred to as the octet rule, a rule that states atoms tend to form bonds until they have eight electrons in their outermost shell.
Hydrogen, on the other hand, follows the duet rule and needs only two electrons to fill its outer shell, which corresponds to its maximum capacity. In the molecule H₂S, you will see that each hydrogen atom contributes one electron to help sulfur reach an octet, while sulfur shares its electrons with hydrogen, filling their duet. Therefore, sulfur's need for an octet and hydrogen's requirement for a duet are both satisfied by the formation of two covalent bonds in hydrogen sulfide.
The number of valence electrons determines how an atom will bond with other atoms. Sulfur's six valence electrons mean it needs two more electrons to achieve a full outer shell, totaling eight electrons. This is often referred to as the octet rule, a rule that states atoms tend to form bonds until they have eight electrons in their outermost shell.
Hydrogen, on the other hand, follows the duet rule and needs only two electrons to fill its outer shell, which corresponds to its maximum capacity. In the molecule H₂S, you will see that each hydrogen atom contributes one electron to help sulfur reach an octet, while sulfur shares its electrons with hydrogen, filling their duet. Therefore, sulfur's need for an octet and hydrogen's requirement for a duet are both satisfied by the formation of two covalent bonds in hydrogen sulfide.
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