Problem 117 - Chemistry An Atoms First Approach

Question

Write the formula for each of the following compounds: a. sulfur difluoride b. sulfur hexafluoride c. sodium dihydrogen phosphate d. lithium nitride e. chromium(III) carbonate f. \(\operatorname{tin}(\text { II })\) fluoride g. ammonium acetate h. ammonium hydrogen sulfate i. cobalt(III) nitrate J. mercury(I) chloride k. potassium chlorate 1\. sodium hydride

Step-by-Step Solution

Answer

a. \(SF_2\) b. \(SF_6\) c. \(NaH_2PO_4\) d. \(Li_3N\) e. \(Cr_2(CO_3)_3\) f. \(SnF_2\) g. \((NH_4)CH_3COO\) h. \((NH_4)HSO_4\) i. \(Co(NO_3)_3\) j. \(HgCl\) k. \(KClO_3\) l. \(NaH\)

Step 1: a. Sulfur difluoride

Sulfur is represented by the symbol S. Fluorine is represented by the symbol F. "Di" means two. Sulfur forms a -2 charge when combined with Fluorine, which forms a -1 charge. To balance the charges, we need one sulfur atom and two fluorine atoms. Thus, the formula for sulfur difluoride is \(SF_2\).

Step 2: b. Sulfur hexafluoride

Similar to sulfur difluoride, sulfur is represented by the symbol S, and fluorine is represented by the symbol F. "Hexa" means six. In this case, sulfur forms a +6 charge and fluorine forms a -1 charge. We need one sulfur atom and six fluorine atoms to balance the charges. So, the formula for sulfur hexafluoride is \(SF_6\).

Step 3: c. Sodium dihydrogen phosphate

Sodium is represented by the symbol Na, hydrogen by the symbol H, and phosphate by the symbol \(PO_4\). Sodium forms a +1 charge, Hydrogen forms a +1 charge and phosphate forms a -3 charge. "Di" means two, referring to two hydrogen atoms. To balance the charges, we need one sodium atom, two hydrogen atoms, and one phosphate atom. Therefore, the formula for sodium dihydrogen phosphate is \(NaH_2PO_4\).

Step 4: d. Lithium nitride

Lithium is represented by the symbol Li and nitrogen by the symbol N. Lithium forms a +1 charge, and nitrogen forms a -3 charge. To balance the charges, we need three lithium atoms and one nitrogen atom. The formula for lithium nitride is \(Li_3N\).

Step 5: e. Chromium(III) carbonate

Chromium is represented by the symbol Cr and carbonate by the symbol \(CO_3\). Chromium(III) refers to a chromium ion with a +3 charge, and carbonate has a -2 charge. To balance the charges, we need two chromium atoms and three carbonate atoms. Therefore, the formula for chromium(III) carbonate is \(Cr_2(CO_3)_3\).

Step 6: f. Tin(II) fluoride

Tin is represented by the symbol Sn and fluorine by the symbol F. Tin(II) refers to a tin ion with a +2 charge, and fluorine forms a -1 charge. To balance the charges, we need one tin atom and two fluorine atoms. The formula for tin(II) fluoride is \(SnF_2\).

Step 7: g. Ammonium acetate

Ammonium is represented by the symbol \(NH_4\), and acetate is represented by the symbol \(CH_3COO\). Ammonium forms a +1 charge and acetate forms a -1 charge. Since the charges are already balanced, the formula for ammonium acetate is \((NH_4)CH_3COO\).

Step 8: h. Ammonium hydrogen sulfate

Ammonium is represented by the symbol \(NH_4\), and hydrogen sulfate is represented by the symbol \(HSO_4\). Ammonium forms a +1 charge and hydrogen sulfate forms a -1 charge. Since the charges are already balanced, the formula for ammonium hydrogen sulfate is \((NH_4)HSO_4\).

Step 9: i. Cobalt(III) nitrate

Cobalt is represented by the symbol Co and nitrate by the symbol \(NO_3\). Cobalt(III) refers to a cobalt ion with a +3 charge, and nitrate has a -1 charge. To balance the charges, we need one cobalt atom and three nitrate atoms. The formula for cobalt(III) nitrate is \(Co(NO_3)_3\).

Step 10: j. Mercury(I) chloride

Mercury is represented by the symbol Hg and chloride by the symbol Cl. Mercury(I) refers to a mercury ion with a +1 charge, and chloride forms a -1 charge. To balance the charges, we need one mercury atom and one chloride atom. The formula for mercury(I) chloride is \(HgCl\).

Step 11: k. Potassium chlorate

Potassium is represented by the symbol K, and chlorate is represented by the symbol \(ClO_3\). Potassium forms a +1 charge, and chlorate forms a -1 charge. Since the charges are already balanced, the formula for potassium chlorate is \(KClO_3\).

Step 12: 1. Sodium hydride

Sodium is represented by the symbol Na and hydrogen by the symbol H. Sodium forms a +1 charge, and hydrogen forms a -1 charge. Since the charges are already balanced, the formula for sodium hydride is \(NaH\).

Key Concepts

Ionic Compounds

Ionic compounds are formed when positively charged ions, known as cations, are attracted to negatively charged ions, known as anions. This attraction occurs due to the electrostatic forces between oppositely charged ions, creating a stable compound.

For example, sodium chloride ( NaCl ) is a classic ionic compound, where sodium (Na) acts as a cation with a +1 charge and chloride (Cl) acts as an anion with a -1 charge.

• Ionic compounds usually consist of a metal and a non-metal.
• They have high melting and boiling points because of the strong forces between ions.
• They often form crystalline structures.

Writing the formula for ionic compounds involves balancing the total positive and negative charges to ensure neutrality.

Molecular Compounds

Molecular compounds, also known as covalent compounds, form when two or more non-metals share electrons to achieve full outer electron shells. This sharing creates a stable compound.

Sulfur hexafluoride ( SF_6 ) is a molecular compound where sulfur shares electrons with six fluorine atoms.

• These compounds typically have lower melting and boiling points compared to ionic compounds.
• They may be gases, liquids, or low melting point solids.
• Molecular compounds often display distinct properties depending on their structure and bonding.

When naming molecular compounds, prefixes like "di-" and "hexa-" are used to denote the number of each type of atom present in the compound.

Charge Balance

Charge balance is a fundamental concept in chemistry, particularly when determining the chemical formulas of compounds.
It ensures that the total positive charge and total negative charge in a compound are equal, resulting in an overall neutral compound.

For instance, in lithium nitride ( Li_3N ), three lithium ions each with a +1 charge balance the -3 charge of a single nitrogen ion.

• This principle governs the formation of both ionic and polyatomic compounds.
• Aids in predicting the stoichiometry of reactions involving ions.

Accurately applying charge balance is key in writing correct chemical formulas.

Polyatomic Ions

Polyatomic ions are ions composed of two or more atoms covalently bonded, that collectively carry a charge, acting as a single ion.
A common example is the phosphate ion ( PO_4^{3-} ) found in sodium dihydrogen phosphate ( NaH_2PO_4 ).

Understanding these ions is critical for predicting compound properties and reactions.

• Polyatomic ions can form ionic bonds with other ions to create complex compounds.
• Names of polyatomic ions often end in "-ate" or "-ite,” such as sulfate ( SO_4^{2-} ) or nitrite ( NO_2^{-} ).
• They frequently appear in various biological and industrial processes.

Mastering polyatomic ions helps with both writing chemical formulas and understanding chemical nomenclature.