Question

Which of the following compounds are likely to have covalent bonds? (a) \(\mathrm{HF}\) (c) \(\mathrm{NCl}_{3}\) (e) \(\mathrm{CF}_{4}\) (b) \(\mathrm{NaF}\) (d) \(\mathrm{MgBr}_{2}\)

Short answer

HF, NCl3 and CF4 are likely to be covalent compounds because they are composed of non-metal elements. NaF and MgBr2 are not likely to be covalent compounds because they are composed of metals and non-metals.

Step-by-step solution

HF

Hydrogen (H) and Fluorine (F) are both non-metals. Compounds formed between non-metals generally form covalent bonds. Therefore, HF is likely to be a covalent compound.

NCl3

Nitrogen (N) and Chlorine (Cl) are both non-metals. Compounds formed between non-metals generally form covalent bonds. Therefore, NCl3 is likely to be a covalent compound.

CF4

Carbon (C) and Fluorine (F) are both non-metals. Compounds formed between non-metals generally form covalent bonds. Therefore, CF4 is likely to be a covalent compound.

NaF

Sodium (Na) is a metal and Fluorine (F) is a non-metal. Compounds formed between metals and non-metals generally form ionic bonds. Therefore, NaF is not likely to be a covalent compound.

MgBr2

Magnesium (Mg) is a metal and Bromine (Br) is a non-metal. Compounds formed between metals and non-metals generally form ionic bonds. Therefore, MgBr2 is not likely to be a covalent compound.

Key concepts

Chemical Compounds

Chemical compounds are substances formed when two or more elements are chemically bonded together. These compounds can consist of atoms that are bonded in various ways, leading to different types of chemical bonds.
Depending on the nature of the elements involved and how they share or exchange electrons, chemical compounds can be categorized into two main types: covalent compounds and ionic compounds.

• Covalent compounds: These are formed when two or more non-metal elements share electrons. The shared electrons allow each atom to attain a stable electron configuration, resembling that of noble gases.
• Ionic compounds: These occur when a metal atom donates electrons to a non-metal atom, creating ions that attract each other due to opposite charges. This electron transfer leads to the formation of ionic bonds.

In the case of covalent compounds like \(\text{HF}, \text{NCl}_3, \text{CF}_4\) from the exercise, the non-metals involved share electrons to stabilize each other. Conversely, compounds like \(\text{NaF}\) and \(\text{MgBr}_2\) involve metals interacting with non-metals, thus forming ionic compounds. Both types of compounds are fundamental to chemistry and have distinct properties and behaviors.

Non-metals

Non-metals are elements usually found on the right side of the periodic table and include elements like hydrogen, carbon, nitrogen, and the halogens (like fluorine and chlorine). These elements are characterized by their tendency to gain electrons to fill their outer electron shells.

• They are generally poor conductors of heat and electricity.
• Non-metals have higher electronegativities than metals, enabling them to attract electrons when forming bonds.
• Many non-metals exist in various states at room temperature: gases (e.g., oxygen), liquids (e.g., bromine), or solids (e.g., carbon).

When non-metals combine, they usually form covalent bonds by sharing electrons. This shared approach fulfills the non-metals’ quest for a stable electron configuration. For instance, hydrogen and fluorine in \(\text{HF}\), and nitrogen and chlorine in \(\text{NCl}_3\) share electrons, forming covalent bonds. This intrinsic property of non-metals highlights their role in creating a diverse array of covalent compounds with distinctive chemical properties.

Ionic Bonds

Ionic bonds are a type of chemical bond formed through the electrostatic attraction between oppositely charged ions. This bond occurs when an electron transfer happens between a metal and a non-metal. The metal loses electrons to form a positively charged ion (cation), while the non-metal gains these electrons to become a negatively charged ion (anion).

• The strength of the ionic bond relies heavily on the charges and sizes of the ions.
• Common characteristics of ionic compounds include high melting and boiling points and being good conductors of electricity when melted or dissolved in water.

In the examples from the exercise, \(\text{NaF}\) and \(\text{MgBr}_2\), sodium and magnesium are metals that donate electrons to the non-metals fluorine and bromine respectively, creating ionic bonds. These types of bonds result in compounds with crystalline structures that are typically hard and brittle. Understanding ionic bonds is crucial in predicting the behavior and properties of a wide range of chemical compounds.