Question

Write the formula for each of the following compounds. (a) potassium bromite (b) calcium bromide (c) sodium periodate (d) magnesium hypochlorite

Short answer

Based on the step-by-step solutions above, provide the chemical formulas for the following compounds: a) Potassium Bromite: KBrO2 b) Calcium Bromide: CaBr2 c) Sodium Periodate: NaIO4 d) Magnesium Hypochlorite: Mg(ClO)2

Step-by-step solution

(a) Potassium Bromite

To find the formula for potassium bromite, first identify the ions involved: 1. Potassium ion (K) has a charge of +1. 2. Bromite ion (BrO2) has a charge of -1. Now combine the ions in a way that their charges cancel each other out, resulting in a neutral compound: (K^+1) + (BrO2^-1) => KBrO2 So, the formula for potassium bromite is KBrO2.

(b) Calcium Bromide

To find the formula for calcium bromide, first identify the ions involved: 1. Calcium ion (Ca) has a charge of +2. 2. Bromide ion (Br) has a charge of -1. Now combine the ions in a way that their charges cancel each other out, resulting in a neutral compound: (Ca^+2) + 2 (Br^-1) => CaBr2 So, the formula for calcium bromide is CaBr2.

(c) Sodium Periodate

To find the formula for sodium periodate, first identify the ions involved: 1. Sodium ion (Na) has a charge of +1. 2. Periodate ion (IO4) has a charge of -1. Now combine the ions in a way that their charges cancel each other out, resulting in a neutral compound: (Na^+1) + (IO4^-1) => NaIO4 So, the formula for sodium periodate is NaIO4.

(d) Magnesium Hypochlorite

To find the formula for magnesium hypochlorite, first identify the ions involved: 1. Magnesium ion (Mg) has a charge of +2. 2. Hypochlorite ion (ClO) has a charge of -1. Now combine the ions in a way that their charges cancel each other out, resulting in a neutral compound: (Mg^+2) + 2 (ClO^-1) => Mg(ClO)2 So, the formula for magnesium hypochlorite is Mg(ClO)2.

Key concepts

Ionic Compounds

Ionic compounds are composed of ions—that is, atoms or molecules that have gained or lost electrons, resulting in a net positive or negative charge. The key feature of an ionic compound is the presence of both positively charged ions (cations) and negatively charged ions (anions). These compounds are held together by the electrostatic attraction between the opposite charges, known as ionic bonding.

For example, when sodium (Na), a metal, reacts with chlorine (Cl), a non-metal, the sodium atom donates an electron, becoming a Na^+ cation, while the chlorine atom gains an electron, becoming a Cl^- anion. As a result, they combine to form sodium chloride (NaCl), an ionic compound. Ionic compounds typically have high melting and boiling points, and when dissolved in water, they can conduct electricity due to the mobility of ions.

Valency and Charge Balancing

Valency, also known as oxidation state, refers to the combining power of an element, especially with respect to the number of hydrogen atoms it can combine with or displace to form a compound. In ionic compounds, this concept is essential as it guides the balancing of charges between the cations and anions to form a neutral compound.

To write the correct formula for an ionic compound, one must balance the total positive charge of the cations with the total negative charge of the anions. If the charges do not match, it's necessary to determine the smallest ratio of ions that will balance out the charges. This often requires using subscripts in the chemical formula to indicate the number of each ion needed to achieve neutrality.

For instance, with magnesium hypochlorite from the exercise, the magnesium ion (Mg) has a valency of +2, and the hypochlorite ion (ClO) has a valency of -1. To achieve charge balance, two hypochlorite ions are needed for every magnesium ion, resulting in the formula Mg(ClO)2.

Compound Nomenclature

The nomenclature of chemical compounds is a systematic way of naming chemicals so that scientists can communicate with precision. Each part of a compound's name reveals something about its structure or composition. Ionic compounds are usually named by stating the cation first and anion second.

Monatomic Ions

For monatomic ions, the cation's name is the same as the element, while the anion's name is formed by dropping the ending of the element's name and adding '-ide.' For example, NaCl is named sodium chloride.

Polyatomic Ions

For polyatomic ions, which are ions composed of more than one atom, specific names are used based on their composition and oxidation state, such as sulfate (SO4^2-) or nitrate (NO3^-). In the exercise's case, 'bromite' indicates the BrO2^- ion, and 'periodate' refers to the IO4^- ion. Therefore, the name reflects the polyatomic ions bromite and periodate, leading to the names potassium bromite (KBrO2) and sodium periodate (NaIO4), respectively.