Question

Classify each of the following substances according to the primary type of bonding. (a) \(\mathrm{HCN}\) (c) \(S_{8}\) (e) \(\mathrm{CoCl}_{2}\) (b) \(\mathrm{AgCl}\) (d) \(\mathrm{CH}_{4}\)

Short answer

The primary type of bonding in HCN and CH4 is covalent, in CoCl2 and AgCl is ionic, and in S8 is also covalent.

Step-by-step solution

Identify the Bonding in HCN

HCN (hydrogen cyanide) is a molecule formed from Hydrogen (H), a non-metal, and Cyanide (CN), which is a polyatomic ion made up of Carbon (C) and Nitrogen (N), both non-metals. Therefore, its bonding is primarily covalent.

Identify the Bonding in S8

S8 molecules are formed by eight sulfur atoms (S). Since sulfur is a non-metal, and the molecule is formed from atoms of the same element, its bonding is also covalent.

Identify the Bonding in CoCl2

CoCl2 (cobalt(II) chloride) is a compound made of Cobalt (Co), a metal, and Chlorine (Cl), a non-metal. As metals and non-metals form ionic bonds, through the transfer of electrons, CoCl2 exhibits primarily ionic bonding.

Identify the Bonding in AgCl

AgCl (silver chloride) is a compound formed by Silver (Ag), a metal, and Chlorine (Cl), a non-metal. Like prior, the bond is Ionic due to the transfer of electrons between metal and non-metal.

Identify the Bonding in CH4

CH4 (methane) is a molecule made up of Carbon (C) and Hydrogen (H), both non-metals. Therefore, it contains covalent bonding as it involves the sharing of electrons between non-metals.

Key concepts

Covalent Bonding

When atoms connect by sharing electrons, they form a covalent bond, which is a strong bond between two non-metals. This kind of bonding is based on the mutual attraction of the atoms for the shared pair of electrons.

For example, in hydrogen cyanide (\textnormal{HCN}), the bond between hydrogen and cyanide, and in methane (\textnormal{CH}\(_4\)), the bonds between carbon and hydrogen are covalent. These atoms share their electrons in order to achieve a fuller outer electron shell, akin to that of noble gases, which is a state of greater stability.

Understanding the behavior of covalent compounds includes examining how atoms attain the octet rule, which means having eight electrons in their valence shell. The number of shared electron pairs varies, leading to single, double, or even triple bonds, like in \textnormal{HCN}.

Ionic Bonding

Ionic bonding, on the other hand, takes place when there is a complete transfer of electrons from one atom to another, typically occurring between metals and non-metals. The metals, losing electrons, become positively charged ions (cations), while the non-metals, gaining electrons, turn into negatively charged ions (anions).

For instance, in the compound cobalt(II) chloride (\textnormal{CoCl}\(_2\)), cobalt gives up electrons to form a cation, and chlorine accepts these electrons to form an anion. This electron transfer leads to an electrostatic attraction between the ions, resulting in an ionic bond. Ionic compounds like \textnormal{CoCl}\(_2\) and silver chloride (\textnormal{AgCl}) often form crystalline structures and exhibit properties such as high melting points and the ability to conduct electricity when dissolved in water.

Chemical Compounds

Chemical compounds are substances composed of two or more different types of atoms bonded together chemically. The properties and behavior of chemical compounds are determined largely by the type of chemical bonding they exhibit.

Compounds like \textnormal{HCN} and \textnormal{CH}\(_4\), with covalent bonds, tend to have distinct molecular structures and generally do not conduct electricity. In contrast, ionic compounds like \textnormal{CoCl}\(_2\) and \textnormal{AgCl} form extensive ionic lattices and typically dissolve in water to produce ions that conduct electricity.

Understanding the bonding in chemical compounds allows us to predict their properties and reactions. When students can classify these bonds, as seen in the textbook exercise, they are better equipped to comprehend chemical reactions and the compounds' potential uses in various applications.