Bonding Preferences - Online Tutor, Practice Problems & Exam Prep

Understanding bonding preferences is crucial in predicting the number of bonds and nonbonding electrons in molecular compounds. Elements in groups 1A to 4A typically form bonds equal to their group number, while those in groups 5A to 7A bond based on achieving a stable octet. For example, nitrogen forms three bonds, oxygen two, and halogens one. Lone pairs are nonbonding electrons, with nitrogen having one, oxygen two, and halogens three. This knowledge is essential for drawing accurate molecular structures and understanding chemical bonding dynamics.

Bonding Preferences Concept 1

Now when it comes to bonding preferences, realize that we can predict the number of bonds and non-bonding electrons in a molecular compound. Now when it comes to these non-bonding electrons, they're just electrons that do not participate in bonding with other elements. And we can say here that a lone pair is just a pair of these non-bonding electrons. Now, if we take a look here, we have some common bonding preferences. So we have from groups 1a to 7a, and here we have representative elements for each group. Realize here that when it comes to group 7a, to represent a halogen, I can use the variable of x, which stands in for fluorine, chlorine, bromine, and iodine.

Here, when we talk about bonding preferences, we're going to say here that for rule 1, we're gonna say group 1a to 4a elements, it's pretty simple. We're gonna say the number of bonds that they prefer is equal to their group number. So hydrogen, which is in group 1a, preferably wants to make one bond. And one important thing here is, when we start drawing molecular compounds later on, realize that hydrogen never goes in the center of any of those compounds. Beryllium is in group 2a, so it wants to make 2 bonds. Boron is in group 3a, so it wants to make 3. Now, carbon is incredibly important. Carbon wants to make 4 bonds, even if that means bonding with itself.

Now, for groups 5a to 7a, we go by rule 2. Here we're going to say that the number of bonds equals the number of electrons needed for a stable electron configuration or arrangement. So, again, groups 1a to 4a, it's based on group number. And then, we're going to say here that nitrogen, which is in group 5a, has 5 valence electrons, so it comes in with 5. But if it wants to follow the octet rule, it wants to get to 8 valence electrons. By forming bonds with surrounding elements, it's able to pick up 3 more. So that's why it wants to make 3 bonds. Oxygen's group 6a, so it has 6 valence electrons that it brings to the table, and it picks up the 2 additional ones that it needs by forming 2 bonds to surrounding elements. And then the halogens as surrounding elements only make a single bond. They come in with 7 valence electrons because they're in group 7a. So to pick up that 8th electron they need, they form one bond to a surrounding element.

Now, if we look here in terms of lone pairs, we're gonna say that the first four groups have no lone pairs. But then groups 5a to 7a, here we have 1 lone pair on nitrogen, then we have 2 lone pairs on oxygen, and then we have 1, 2, 3 lone pairs on a halogen when it's a surrounding element. So, just remember, when it comes to bonding preferences, these are the typical ones that we have for elements from groups 1a to 7a of the periodic table.

Bonding Preferences Example 1

Here it asks, how many bonds and lone pairs are typically found around an oxygen atom? Now we're going to say here, if we look up above, that'd be a little bit of cheating, so let's just think about this. Oxygen is in group 6a. Remember, from elements from groups 5a to 7a, the number of bonds they make is based on how many electrons they need to get to the ideal electron arrangement. Oxygen is in group 6a, so it has 6 valence electrons. If it wants to follow the octet rule to get 8 valence electrons around it, it wants to make 2 bonds, and thereby pick up 2 additional electrons. So here we can say the number of bonds an oxygen atom typically makes is 2, and then we can say the number of lone pairs around it are 1, 2. These lone pairs are not connecting to another element. So here, definitely the answer is option b.

How many bonds and nonbonding electrons can be found around Si atoms?

• A. 4, 4
• B. 2, 4
• C. 3, 2
• D. 4, 0

How many bonds and lone pairs can be found around Mg atoms?

a) 2, 1                    b) 2, 0                    c) 3, 1                     d) 3, 0

• A. 2, 1
• B. 2, 0
• C. 3, 1
• D. 3, 0

Here’s what students ask on this topic:

What are bonding preferences in chemistry?

Bonding preferences in chemistry refer to the typical number of bonds that elements form and the number of nonbonding electrons (lone pairs) they possess in molecular compounds. Elements in groups 1A to 4A of the periodic table form bonds equal to their group number. For example, hydrogen (group 1A) forms one bond, beryllium (group 2A) forms two bonds, boron (group 3A) forms three bonds, and carbon (group 4A) forms four bonds. Elements in groups 5A to 7A form bonds to achieve a stable octet configuration. For instance, nitrogen (group 5A) forms three bonds, oxygen (group 6A) forms two bonds, and halogens (group 7A) form one bond. Lone pairs are nonbonding electrons, with nitrogen having one, oxygen two, and halogens three.

How do elements in groups 1A to 4A determine their bonding preferences?

Elements in groups 1A to 4A determine their bonding preferences based on their group number. The number of bonds they prefer to form is equal to their group number. For example, hydrogen (group 1A) prefers to form one bond, beryllium (group 2A) prefers to form two bonds, boron (group 3A) prefers to form three bonds, and carbon (group 4A) prefers to form four bonds. This rule helps predict the bonding behavior of these elements in molecular compounds.

Why do elements in groups 5A to 7A form bonds based on achieving a stable octet?

Elements in groups 5A to 7A form bonds based on achieving a stable octet to attain a stable electron configuration. These elements have 5, 6, or 7 valence electrons, respectively, and need to gain additional electrons to reach a total of 8 valence electrons, which is a stable configuration. For example, nitrogen (group 5A) has 5 valence electrons and forms three bonds to gain 3 more electrons, achieving a stable octet. Oxygen (group 6A) forms two bonds to gain 2 more electrons, and halogens (group 7A) form one bond to gain 1 more electron.

What are lone pairs, and how do they relate to bonding preferences?

Lone pairs are pairs of nonbonding electrons that do not participate in bonding with other elements. They are important in determining the shape and reactivity of molecules. In terms of bonding preferences, elements in groups 5A to 7A have lone pairs in addition to their bonding electrons. For example, nitrogen (group 5A) has one lone pair, oxygen (group 6A) has two lone pairs, and halogens (group 7A) have three lone pairs. These lone pairs influence the geometry and properties of the molecules they form.

How do you predict the number of bonds an element will form in a molecular compound?

To predict the number of bonds an element will form in a molecular compound, you need to consider its group number and its need to achieve a stable electron configuration. For elements in groups 1A to 4A, the number of bonds is equal to their group number. For elements in groups 5A to 7A, the number of bonds is determined by the number of electrons needed to achieve a stable octet. For example, nitrogen (group 5A) forms three bonds, oxygen (group 6A) forms two bonds, and halogens (group 7A) form one bond.