Question

Give the chemical formula for each of the following ionic compounds: (a) sodium phosphate, (b) zinc nitrate, (c) barium bromate, \((\mathbf{d})\) iron(II) perchlorate, \((\mathbf{e})\) cobalt(II) hydrogen carbonate, (f) chromium(III) acetate, \((\mathbf{g})\) potassium dichromate.

Short answer

The chemical formulas for the given ionic compounds are: (a) \(\ce{Na3PO4}\), (b) \(\ce{Zn(NO3)2}\), (c) \(\ce{Ba(BrO3)2}\), (d) \(\ce{Fe(ClO4)2}\), (e) \(\ce{Co(HCO3)2}\), (f) \(\ce{Cr(CH3COO)3}\), and (g) \(\ce{K2Cr2O7}\).

Step-by-step solution

(a) Sodium Phosphate

The ions in this compound are sodium (Na+) and phosphate (PO4^3-). To balance the charges, we need 3 sodium ions for each phosphate ion. The chemical formula is: \[ \ce{Na3PO4} \]

(b) Zinc Nitrate

The ions in this compound are zinc (Zn^2+) and nitrate (NO3^-). To balance the charges, we need 2 nitrate ions for each zinc ion. The chemical formula is: \[ \ce{Zn(NO3)2} \]

(c) Barium Bromate

The ions in this compound are barium (Ba^2+) and bromate (BrO3^-). To balance the charges, we need 2 bromate ions for each barium ion. The chemical formula is: \[ \ce{Ba(BrO3)2} \]

(d) Iron(II) Perchlorate

Iron(II) means that iron has a +2 charge (Fe^2+), and the ion in this compound is perchlorate (ClO4^-). To balance the charges, we need 2 perchlorate ions for each iron(II) ion. The chemical formula is: \[ \ce{Fe(ClO4)2} \]

(e) Cobalt(II) Hydrogen Carbonate

Cobalt(II) means that cobalt has a +2 charge (Co^2+), and the ion in this compound is hydrogen carbonate (HCO3^-). To balance the charges, we need 2 hydrogen carbonate ions for each cobalt(II) ion. The chemical formula is: \[ \ce{Co(HCO3)2} \]

(f) Chromium(III) Acetate

Chromium(III) means that chromium has a +3 charge (Cr^3+), and the ion in this compound is acetate (CH3COO^-). To balance the charges, we need 3 acetate ions for each chromium(III) ion. The chemical formula is: \[ \ce{Cr(CH3COO)3} \]

(g) Potassium Dichromate

The ions in this compound are potassium (K+) and dichromate (Cr2O7^2-). To balance the charges, we need 2 potassium ions for each dichromate ion. The chemical formula is: \[ \ce{K2Cr2O7} \]

Key concepts

Ionic Compounds

Ionic compounds are formed from the electrical attraction between oppositely charged ions. These ions are formed when an atom loses or gains electrons to achieve a full outer shell, very much like a soccer team aiming for a full roster. For instance, when a sodium atom loses an electron, it becomes positively charged (Na extsuperscript{+}), while a chlorine atom that gains an electron becomes negatively charged (Cl extsuperscript{-}). These opposite charges attract, pulling the ions together to form ionic sodium chloride (NaCl).

Ionic compounds typically have high melting and boiling points and can conduct electricity when molten or dissolved in water. This stems from the strong force between the ions, making them cling tightly to each other. Understanding the formation of ionic compounds is key to exploring chemical reactions and transformations.

Charge Balancing

Charge balancing involves ensuring that the total positive and negative charges in an ionic compound are equal. This balance is crucial because compounds typically exist in a neutral state. Think of it like crafting a puzzle where each piece must perfectly match the others.

To achieve this balance, you need to determine the charge of each ion involved in forming the compound. For example, in zinc nitrate (\[\ce{Zn(NO3)2}\]), zinc has a +2 charge, and nitrate has a -1 charge. To balance the total charges, it takes two nitrate ions to offset one zinc ion, ensuring that the overall charge remains neutral.

This process helps us derive the correct chemical formula by clearly understanding how many ions are required to neutralize the charges.

Polyatomic Ions

Polyatomic ions are ions composed of two or more atoms covalently bonded, that act as a single charged entity. Common examples include sulfate (SO extsubscript{4} extsuperscript{2-}), nitrate (NO extsubscript{3} extsuperscript{-}), and ammonium (NH extsubscript{4} extsuperscript{+}). These ions can combine with other simple ions to form ionic compounds, much like different groups teaming up to form a club.

When combining polyatomic ions with other ions, it's essential to consider their overall charge to achieve charge balance. For example, the ammonium ion itself acts just like a single ion with a positive charge. This characteristic plays a critical role in writing chemical formulas, as the polyatomic ion needs the correct number of partner ions to balance out its charge.

Chemical Nomenclature

Chemical nomenclature is the systematic naming of chemical compounds following specific rules. This is similar to giving each chemical compound a distinct name, just like we name our pets to distinguish them easily from one another.

The nomenclature for ionic compounds involves naming the cation (positively charged ion) first, followed by the anion (negatively charged ion). For example, in sodium chloride, 'sodium' denotes Na extsuperscript{+}, while 'chloride' represents Cl extsuperscript{-}.

When dealing with compounds that have metals with variable charges, such as iron, the charge is indicated in parentheses using Roman numerals (e.g., iron(II) for Fe extsuperscript{2+} and iron(III) for Fe extsuperscript{3+}).

The systematic approach in chemical nomenclature aids chemists in easily identifying and communicating the component ion of the compound, ensuring clarity and precision in scientific messaging.