Question

For each of the following pairs of elements, state whether the binary compound they form is likely to be ionic or covalent. Write the empirical formula and name of the compound: (a) I and \(\mathrm{Cl}\), (b) \(\mathrm{Mg}\) and \(\mathrm{F}\).

Short answer

For pair (a) I and Cl, the bond type is covalent, the formula is ICl and the name is iodine chloride. For pair (b) Mg and F, the bond type is ionic, the formula is MgF2 and the name is magnesium fluoride.

Step-by-step solution

Determine the type of bond for pair (a) I and Cl

Both Iodine (I) and Chlorine (Cl) are nonmetals. Therefore, the bond that forms between them is covalent.

Write the empirical formula and name for pair (a)

In a covalent bond, the empirical formula is simply the combination of the elements. Therefore, the empirical formula for a compound of iodine and chlorine is ICl. The name of the compound follows the pattern 'first element + second element + ide', therefore it is named 'iodine chloride'.

Determine the type of bond for pair (b) Mg and F

Magnesium (Mg) is a metal, and Fluorine (F) is a nonmetal. Therefore, the bond that forms between them is ionic.

Write the empirical formula and name for pair (b)

In an ionic bond, the metal loses electrons to the non-metal till both have a full outer shell. Magnesium (Mg) needs to lose two electrons to have full outer shell. Fluorine (F), on the other hand, needs to gain one electron to have a full outer shell. Therefore, one magnesium atom will combine with two fluorine atoms to form MgF2. The name of the compound is 'magnesium fluoride'.

Key concepts

Empirical Formula

The empirical formula of a compound provides the simplest whole-number ratio of atoms of each element present in the compound. It does not necessarily correspond to the actual numbers of atoms but gives an idea of the relative proportion in which the elements combine. For instance, in the binary compound of iodine and chlorine, which is covalent, the empirical formula is \( \text{ICl} \). This indicates one iodine atom is paired with one chlorine atom. In the example of magnesium and fluorine, which form an ionic compound, the empirical formula is \( \text{MgF}_2 \). This shows one magnesium atom combining with two fluorine atoms to maintain electrically neutral compounds. Always remember, empirical formulas are key in understanding the basic composition of compounds, whether they are ionic or covalent in nature.

Binary Compounds

Binary compounds are composed of two different elements. The nature of the compound, whether ionic or covalent, depends largely on the types of elements that combine. For example, a binary compound can be a combination of metals with nonmetals or nonmetals with nonmetals.

• If a nonmetal like chlorine combines with another nonmetal like iodine, the resulting binary compound, iodine chloride, will exhibit covalent bonding.
• Conversely, if a metal like magnesium bonds with a nonmetal such as fluorine, they form an ionic bond, resulting in a compound called magnesium fluoride.

Determining whether a binary compound is likely ionic or covalent helps in predicting its chemical behavior and properties.

Ionic Compounds

Ionic compounds are formed through the transfer of electrons from a metal to a nonmetal, resulting in the formation of ions. These oppositely charged ions attract each other to form a compound. A good example is shown in the compound formed by magnesium and fluorine. Magnesium, a metal, loses two electrons to become \( Mg^{2+} \), while each fluorine atom gains one electron to form \( F^- \). Therefore, two fluorine ions will bond with one magnesium ion to form \( \text{MgF}_2 \).
Characteristics of ionic compounds include:

• High melting and boiling points due to strong ionic bonds.
• Conductive when dissolved in water, as ions are free to move and carry charge.
• Generally solid at room temperature.

Understanding these properties helps in identifying ionic compounds and predicting their reactions.

Covalent Compounds

Covalent compounds are made when nonmetal atoms share electrons to achieve a full outer electron shell. The bond formed by sharing electrons between atoms signifies a covalent bond. In our example, the compound formed by iodine and chlorine exemplifies covalent bonding. Each atom shares one electron to create a pair of electrons, commonly represented as \( \text{ICl} \), the empirical formula indicating one iodine atom and one chlorine atom.
Key aspects of covalent compounds include:

• Lower melting and boiling points compared to ionic compounds.
• Often exist as gases or liquids at room temperature.
• Poor electrical conductivity because there are no free ions to carry charge.

Through these properties, covalent compounds can be easily characterized, aiding in understanding their potential applications and interactions in chemistry.