Question

Determine whether each of the following compounds is ionic or covalent and draw an appropriate Lewis structure: a. \(\mathrm{MgS}\) b. \(\mathrm{PI}_{3}\) c. \(\mathrm{SrCl}_{2}\) d. \(\mathrm{CHClO}\) (carbon is the central atom)

Short answer

a. MgS - Ionic, no Lewis structure for ionic compounds. b. PCl3 - Covalent, P is central atom with three P-Cl bonds and one lone pair on P. c. SrCl2 - Ionic, no Lewis structure for ionic compounds. d. CHClO - Covalent, C is central atom with bonds to H, Cl, and a double bond to O, with lone pairs on Cl and O.

Step-by-step solution

Identifying Ionic or Covalent - MgS

To determine if MgS is ionic or covalent, we look at the types of atoms involved. Magnesium (Mg) is a metal, and sulfur (S) is a non-metal. Compounds between metals and non-metals are typically ionic. Therefore, MgS is an ionic compound. For the Lewis structure, we will not draw individual bonds since ionic compounds do not have discrete molecules. Mg has 2 valence electrons and S has 6. Mg will lose 2 electrons to become Mg^2+ and S will gain 2 electrons to become S^2-.

Identifying Ionic or Covalent - PCl3

For PCl3, both phosphorus (P) and chlorine (Cl) are non-metals. Compounds between non-metals are typically covalent. Therefore, PCl3 is a covalent compound. In the Lewis structure for PCl3, P is the central atom and has 5 valence electrons, while each Cl has 7 valence electrons. Each Cl will share one electron with P, resulting in three P-Cl single bonds and one pair of unshared electrons on the P atom.

Identifying Ionic or Covalent - SrCl2

Strontium (Sr) is a metal, and chlorine (Cl) is a non-metal. This means SrCl2 is an ionic compound. For the Lewis structure, we recognize that Sr has 2 valence electrons and each Cl has 7. Sr will lose 2 electrons to form Sr^2+, and each Cl will gain 1 electron to form two Cl^-, resulting in Sr^2+ ion surrounded by two Cl^- ions.

Identifying Ionic or Covalent - CHClO

In CHClO, all atoms involved are non-metals (C, H, Cl, and O). This indicates CHClO is a covalent compound. For the Lewis structure, the central atom C has 4 valence electrons, H has 1, Cl has 7, and O has 6. H will form one bond with C, O will form a double bond with C, and Cl will form a single bond with C. There will also be three lone pairs on Cl and two lone pairs on O.

Key concepts

Ionic and Covalent Compounds

Understanding the difference between ionic and covalent compounds is essential in the study of chemistry. Ionic compounds, such as magnesium sulfide ((MgS)) and strontium chloride ((SrCl_2)), typically form between metals and non-metals. These compounds consist of ions held together by ionic bonds, which are the electrostatic forces of attraction between positively and negatively charged ions.

In contrast, covalent compounds like phosphorus trichloride ((PCl_3)) and carbon monoxide ((CHClO)) are formed between non-metal atoms. These atoms share pairs of electrons to achieve stability, forming what are called covalent bonds.

To determine the type of compound:

• Identify the elements involved.
• Check their position in the periodic table (metals or non-metals).
• Apply the metal-nonmetal rule: metal + non-metal = ionic; non-metal + non-metal = covalent.

Covalent bonding allows for a wide variety of molecular structures and can result in single, double, or triple bonds, while ionic compounds tend to form crystalline lattice structures.

Valence Electrons

Valence electrons are the outermost electrons of an atom and play a pivotal role in chemical bonding. They are the electrons that participate in bond formation. For example, in magnesium sulfide ((MgS)), magnesium has two valence electrons and sulfur has six. During the formation of (MgS), magnesium donates its two valence electrons to sulfur, achieving a full outer shell for the sulfur atom.

In covalent bonding, such as with (PCl_3), atoms share valence electrons. Phosphorus has five valence electrons and chlorine has seven. They share electrons such that each chlorine atom and the phosphorus atom attain a stable electronic configuration.

Valence electrons can be identified by looking at an element's group number on the periodic table:

• Group 1: 1 valence electron
• Group 2: 2 valence electrons
• Groups 13-18: 3-8 valence electrons (subtract 10 from group number)

This simple guideline helps predict how atoms will bond and the type of ions they will form if they are involved in ionic bonding.

Chemical Bonding

Chemical bonding is what enables atoms to come together and form compounds. The two primary types of chemical bonding are ionic and covalent, as seen in the compounds (MgS), (PCl_3), (SrCl_2), and (CHClO). Ionic bonding occurs when there is a complete transfer of electrons from one atom to another, resulting in ions that are held together by the electric force between oppositely charged particles.

Covalent bonding, on the other hand, involves the sharing of electron pairs between atoms. The shared electrons contribute to each atom's valence shell, making them more stable. Depending on how many electrons are shared, we can have single, double, or triple bonds. In (CHClO), the central carbon atom forms single bonds with hydrogen and chlorine and a double bond with oxygen.

Chemical bonds are influenced by the electronegativity of atoms—how strongly they attract electrons. High electronegativity differences typically lead to ionic bonding, while smaller differences favor covalent bonding. This concept is crucial for predicting the types of bonds that will form in a chemical reaction.