Problem 57 - General Chemistry: Principles and Modern Applications

Question

Name these compounds: (a) \(\operatorname{SrO} ;\) (b) \(\mathrm{ZnS} ;\) (c) \(\mathrm{K}_{2} \mathrm{CrO}_{4}\) (d) \(\mathrm{Cs}_{2} \mathrm{SO}_{4} ;(\mathrm{e}) \mathrm{Cr}_{2} \mathrm{O}_{3} ;(\mathrm{f}) \mathrm{Fe}_{2}\left(\mathrm{SO}_{4}\right)_{3} ;(\mathrm{g}) \mathrm{Mg}\left(\mathrm{HCO}_{3}\right)_{2}\) (h) \(\left(\mathrm{NH}_{4}\right)_{2} \mathrm{HPO}_{4} ; \quad\) (i) \(\quad \mathrm{Ca}\left(\mathrm{HSO}_{3}\right)_{2} ; \quad(\mathrm{j}) \quad \mathrm{Cu}(\mathrm{OH})_{2}\) (k) \(\mathrm{HNO}_{3} ;\) (1) \(\mathrm{KClO}_{4} ;\) (m) \(\mathrm{HBrO}_{3} ;\) (n) \(\mathrm{H}_{3} \mathrm{PO}_{3}\).

Step-by-Step Solution

Answer

(a) Strontium Oxide, (b) Zinc Sulphide, (c) Potassium Chromate, (d) Caesium Sulphate, (e) Chromium (III) Oxide, (f) Iron (III) Sulphate, (g) Magnesium Bicarbonate, (h) Ammonium Hydrogen Phosphate, (i) Calcium Bisulphite, (j) Copper (II) Hydroxide, (k) Nitric Acid, (l) Potassium Perchlorate, (m) Bromic Acid, (n) Phosphoric Acid.

Step 1: Identify the type of compound and elements present

Confirm if the compound is ionic (contains a metal and a non-metal) or covalent (contains only non-metals). Then identify the elements present in the compound.

Step 2: Assign correct compound names

Give names to the compounds according to the rules of nomenclature. '-ide' usually comes at the end of non-metals, '-ate' and '-ite' are used for polyatomic ions.

Step 3: Associate names to formulas

Associate the names determined from step2 with the formulas provided in the problem.

Key Concepts

Ionic Compounds

Ionic compounds are formed when metals and non-metals come together. The metal, generally from the left side of the periodic table, loses electrons and forms positive ions while the non-metal, from the right side, gains those electrons, forming negative ions. This exchange creates an electrical attraction between the oppositely charged ions, resulting in an ionic bond.
Here’s how to identify and name ionic compounds:

• Check for a metal and a non-metal in the formula. Examples include \( ext{SrO}\) (Strontium Oxide) and \( ext{ZnS}\) (Zinc Sulfide).
• The name starts with the metal. No need to change its name except when transition metals are involved, then you add roman numerals indicating its charge.
• The non-metal gets an '-ide' suffix. For instance, \( ext{O}\) becomes Oxide and \( ext{S}\) becomes Sulfide.

Naming ionic compounds gets easier with practice, and following these guidelines ensures you recognize the pattern in the formulas.

Covalent Compounds

Covalent compounds involve the sharing of electrons between atoms, usually non-metals. In these compounds, the electrons are not transferred as in ionic bonds, but rather shared to allow each atom to reach a stable electron configuration.
To name covalent compounds, you should:

• Identify the non-metals present. Both elements are non-metals, like in \( ext{HNO}_3\) (Hydrogen Nitrate) despite it technically being an oxyacid.
• Use prefixes to denote the number of atoms present: 'mono-' for one, 'di-' for two, 'tri-' for three, etc. However, 'mono-' is often omitted for the first element.
• The suffix '-ide' is used for the second element, though it's less common in acids and more common in traditional covalent compounds.

The nature of the covalent bond keeps the atoms joined closely together, sharing their electron clouds.

Polyatomic Ions

Polyatomic ions are collections of atoms bonded together that bear a net charge. They act as a single unit and often participate in ionic bonding with metals, forming complex ionic compounds.
Some popular polyatomic ions include nitrate (\( ext{NO}_3^-\)), sulfate (\( ext{SO}_4^{2-}\)), and phosphate (\( ext{PO}_4^{3-}\)). Here’s how they fit into the chemical nomenclature:

• Recognize them within a compound. For example, in \( ext{K}_2 ext{CrO}_4\) (Potassium Chromate), \( ext{CrO}_4^{2-}\) is the chromate ion.
• The suffix '-ate' or '-ite' suggests an oxygen-rich polyatomic ion. 'Ate' indicates more oxygen than 'ite'.
• You name the metal first, followed by the name of the polyatomic ion. This usually sounds exactly like the ion's name itself.

Grasping the nature and naming of polyatomic ions will greatly enhance your understanding of more complex chemical formulas.