Covalent Bonds: Study with Video Lessons, Practice Problems & Examples

Covalent bonding involves the sharing of valence electrons between nonmetals, allowing them to achieve stable electron configurations, following the octet rule or the duet rule for hydrogen. Covalent compounds can exist as solids, liquids, or gases at room temperature, are poor electrical conductors, and typically have lower melting and boiling points. The sharing of electrons enables nonmetals like fluorine to mimic the electron configuration of noble gases, enhancing their stability.

Covalent Bonds Concept 1

So with covalent bonding, we say that a key feature of covalent compounds is where molecular bonds involve sharing valence electrons between nonmetals. Remember, covalent compounds only involve nonmetals. Recall they do this in order to achieve 8 valence electrons or a filled outer shell like the noble gases. Now we're going to say with this idea we have what's called the octet rule and the duet rule. With the octet rule, that's when an element reacts in order to achieve 8 valence electrons. And with the duet rule, this is specifically for the element of hydrogen. Here, it reacts in order to achieve 2 valence electrons. Doing this helps it to establish a filled outer shell like the noble gas of helium. Remember, from hydrogen to helium, hydrogen only needs to gain one more electron to be just like the noble gas of helium. So just remember, nonmetals form bonds in order to obtain electron arrangements like the noble gases. They do this to fulfill either the octet rule or the duet rule in terms of hydrogen.

Covalent Bonds Concept 2

So with the duet rule and the octet rule, remember, hydrogen follows the duet rule. Here we have 2 hydrogens. Both of their electron configurations are s1. If they can gain 1 electron, they can become 1s2 and become just like the noble gas helium. When it comes to covalent bonds, though, there is no transferring of electrons. It's the sharing of valence electrons. So what they do here is that they each share their one valence electron. So basically, they don't have sole possession of both electrons, they're sharing amongst each other. That gives each of them an electron configuration of 1s2, just like the noble gases in terms of helium. Other non-metals, they have more shells and therefore they want to follow the octet rule. If we take a look here at fluorine, fluorine is 1s22s22p5. If it can get to 2p6, it can become just like the noble gas of neon. What each fluorine decides to do is they decide to share their one electron. So here, neither one has sole possession of both electrons within this bond. They're sharing them with each other. And in that way, they each can have the 2p6 electron configuration that they desire. Doing this allows them to have or mimic the electron configuration of neon. So in both instances, the duet rule and the octet rule allow for a noble gas to mimic the electron configuration or electron arrangement of the nearest noble gases to them.

Covalent Bonds Example 1

Which of these elements is unlikely to form covalent bonds? We have sulfur, hydrogen, potassium, argon, and silicon here. Remember, covalent bonds involve the sharing of electrons between nonmetals. So, if we take a look here, sulfur is a nonmetal, so sulfur could form covalent bonds. Hydrogen is a nonmetal. Potassium is a metal; we said that it's between nonmetals. So, it can't ever form covalent bonds. Let's look at the other options. We have argon and then we have silicon. Argon is a nonmetal. Silicon is a metalloid. Now, technically, remember metalloids share characteristics of both metals and nonmetals, and since it's a metalloid and shares some nonmetal characteristics, there is the potential to form covalent bonds. So, e has the potential. c can't ever have the potential in forming covalent bonds because it's strictly a metal. So just remember, when it comes to covalent bonding, it's the sharing of electrons between elements that have nonmetallic characteristics.

Covalent Bonds Concept 3

When it comes to the properties of covalent compounds, we can take a look at their physical states, their conductivity, as well as their temperature. Now we're going to say because of the nature of their sharing of valence electrons, they can exist in any of the three states of matter at room temperature. So they can exist as solids, liquids, or gases. In terms of conductivity, we're going to say that they represent poor electrical conductors, and that's because they're not easily dissolved when I place them in a solvent like water. And then also we're going to say here that in terms of temperature, they tend to have lower melting points and lower boiling points.

Covalent Bonds Example 2

Which of the following compounds is expected to have the lowest boiling point? So here we have LiBr, lithium bromide, we have sulfur dioxide, we have sodium metal, we have zinc chloride, and then we have lead. Alright. So low boiling points are indicative of covalent compounds. Now before we even talk about that, realize that we have sodium metal and we have lead. Metals, when you think about metals in everyday life, you see metal structures, you see that they're pretty strong and rigid. We'd expect them to have higher boiling points. So choices (c) and (e) are out. Choices (a) and (d) are compounds composed of a metal, in this case, lithium and zinc, with a nonmetal in terms of bromine and chlorine. So they would represent ionic compounds. Ionic compounds tend to have higher boiling points. (b) is the answer because we have sulfur with oxygen. We have only nonmetals bonded together. So this represents a covalent compound, which tends to have a lower boiling point.

Here’s what students ask on this topic:

What is a covalent bond and how does it differ from an ionic bond?

A covalent bond involves the sharing of valence electrons between nonmetals, allowing them to achieve stable electron configurations. In contrast, an ionic bond involves the transfer of electrons from one atom to another, typically between a metal and a nonmetal. This transfer creates ions: the metal becomes a positively charged cation, and the nonmetal becomes a negatively charged anion. Covalent bonds result in the formation of molecules, whereas ionic bonds result in the formation of ionic compounds. Covalent compounds generally have lower melting and boiling points and are poor electrical conductors, while ionic compounds have higher melting and boiling points and conduct electricity when dissolved in water.

What is the octet rule and how does it apply to covalent bonding?

The octet rule states that atoms tend to form bonds in such a way that they each have eight valence electrons, achieving a stable electron configuration similar to that of noble gases. In covalent bonding, nonmetals share valence electrons to fulfill the octet rule. For example, in a molecule of fluorine (F₂), each fluorine atom shares one electron with the other, allowing both to achieve the electron configuration of neon (2s²2p⁶). This sharing of electrons helps the atoms achieve a more stable, lower-energy state.

What is the duet rule and which element does it apply to?

The duet rule is a specific case of the octet rule that applies to hydrogen. According to the duet rule, hydrogen atoms form bonds to achieve two valence electrons, mimicking the electron configuration of helium (1s²). For instance, in a hydrogen molecule (H₂), each hydrogen atom shares its single electron with the other, resulting in both atoms having a filled 1s orbital, similar to helium. This sharing of electrons allows hydrogen to achieve a stable, lower-energy state.

What are the properties of covalent compounds?

Covalent compounds exhibit several distinct properties due to the nature of their bonding. They can exist in any of the three states of matter (solids, liquids, or gases) at room temperature. They are generally poor electrical conductors because they do not easily dissolve in solvents like water, and they do not have free ions to carry an electric current. Additionally, covalent compounds typically have lower melting and boiling points compared to ionic compounds, due to the weaker intermolecular forces between their molecules.

How do covalent bonds enable nonmetals to mimic the electron configuration of noble gases?

Covalent bonds enable nonmetals to mimic the electron configuration of noble gases by sharing valence electrons. For example, in a fluorine molecule (F₂), each fluorine atom shares one electron with the other, allowing both to achieve the electron configuration of neon (2s²2p⁶). This sharing of electrons allows the atoms to achieve a stable, lower-energy state similar to that of noble gases, which have complete valence electron shells. This stability is the driving force behind the formation of covalent bonds.