Nitrogen Family Reactions: Videos & Practice Problems

The nitrogen family, or group 5A elements, are characterized by having five valence electrons, leading to diverse chemical behaviors among its members, which include nonmetals, metalloids, and metals. These elements can react with halogens to form trihalides and, in some cases, pentahalides—compounds with three and five halogen atoms, respectively. This is due to the ability of elements from period 3 and lower to have expanded octets, allowing for additional bonding. However, nitrogen, being in period 2, cannot form pentahalides. When trihalides and pentahalides interact with water, they produce oxyacids—covalent compounds with hydrogen atoms bonded to an oxyanion. Trihalides yield oxyacids with three oxygen atoms, while pentahalides result in oxyacids with four oxygen atoms, as the maximum number of oxygens observed in oxyacids is four. It's important to note that nitrogen's trihalides do not participate in these reactions. Understanding these reaction patterns is crucial for predicting the behavior of group 5A elements when they encounter halogens and water.

Nitrogen Family Reactions

The nitrogen family, also known as group 5A of the periodic table, consists of elements characterized by having five valence electrons in their s and p subshells. This unique electron configuration drives their chemical reactivity, particularly in two main types of reactions: those with halogens and those with water.

To initiate reactions with water, group 5A elements first form halides through their interaction with halogens. This step is crucial as it sets the stage for subsequent reactions with water. As we move across the periodic table from groups 1A to 4A and into group 5A, we observe a diverse range of elements. This group includes nonmetals like nitrogen and phosphorus, metalloids such as arsenic and antimony, and the metallic element bismuth. The elements in rows 2 to 6 are of primary interest, while the synthetic elements in row 7 are generally less predictable and not the focus of typical discussions regarding this group.

Understanding the reactions of the nitrogen family is essential for grasping their chemical behavior and applications. The diversity of elements within this group allows for a variety of chemical interactions, making it a fascinating area of study in chemistry.

Reaction with Halogens

The nitrogen family elements, also known as Group 15 elements, react with halogens to form compounds called trihalides and pentahalides. It's important to note that only nonmetals from periods 3 and lower can exhibit expanded octets, allowing them to accommodate more than eight electrons in their valence shell. Since nitrogen is located in period 2, it cannot form pentahalides due to this limitation. Additionally, while bismuth is a member of the nitrogen family, it is metallic and thus excluded from this discussion. However, metalloids like arsenic and antimony can participate in these reactions due to their nonmetal characteristics.

When considering the reaction of a Group 15 element (denoted as E) with a diatomic halogen (represented as X₂), the general reaction can be expressed as:

$$2E + 3X_2 \rightarrow 2EX_3$$

In this balanced equation, two moles of the Group 15 element react with three moles of the diatomic halogen to produce trihalides (EX₃). This trihalid can further react with an additional mole of diatomic halogen to form a pentahalide:

$$EX_3 + X_2 \rightarrow EX_5$$

In this case, the pentahalide is formed with a balanced equation of:

$$EX_3 + X_2 \rightarrow EX_5$$

Thus, to synthesize a pentahalide from a Group 15 element, a total of four moles of diatomic halogens are required: three for the formation of the trihalid and one more for the conversion to the pentahalide. Recognizing these patterns is crucial for understanding the formation of trihalides and pentahalides in chemical reactions involving halogens.

Nitrogen Family Reactions Example

In the reaction between nitrogen and diatomic fluorine, we start with 2 moles of solid nitrogen (N₂) and 3 moles of fluorine (F₂). When a group 5A element, such as nitrogen, reacts with a diatomic halogen, the expected product is a trihalide. In this case, the product formed is nitrogen trifluoride (NF₃).

To ensure the reaction is balanced, we need to account for the number of atoms on both sides. Initially, we have 2 nitrogen atoms from the nitrogen reactant. To balance this, we place a coefficient of 2 in front of NF₃, resulting in 2 NF₃ on the product side. This adjustment gives us a total of 2 nitrogen atoms and 6 fluorine atoms (since each NF₃ contains 3 fluorine atoms, and 2 NF₃ yields 6 fluorines).

On the reactant side, we also have 3 moles of F₂, which provides 6 fluorine atoms (3 F₂ molecules × 2 F per molecule = 6 F). Thus, the balanced equation for the reaction is:

2 N₂ + 3 F₂ → 2 NF₃

This equation illustrates the formation of nitrogen trifluoride, confirming that the reaction adheres to the principles of stoichiometry and the conservation of mass.

Reaction with H2O

In the study of halides, particularly focusing on group 5A elements, we explore the formation of trihalides and pentahalides and their subsequent reactions with water to produce oxyacids. Oxyacids are defined as covalent compounds that consist of a hydrogen atom bonded to an oxyanion. It is important to note that the trihalogens of nitrogen do not participate in these reactions.

When trihalides react with water, they yield oxyacids characterized by the number of halogens present. Specifically, trihalides, which contain three halogens, produce oxyacids with three oxygen atoms. For example, if we denote the group 5A element as 'E', the resulting oxyacid can be represented as H₃EO₃. Additionally, this reaction generates a hydrogen halide as a byproduct, and the balanced equation for this reaction would be 1H₃E + 3H₂O → H₃EO₃ + 3HX.

On the other hand, pentahalides, which contain five halogens, react with water to form oxyacids with four oxygen atoms, as oxyacids do not extend to five oxygens. Thus, the oxyacid formed from a pentahalide can be represented as H₃EO₄. Similar to the trihalides, a hydrogen halide is also produced in this reaction, and the balanced equation would be 1H₃E + 4H₂O → H₃EO₄ + 5HX.

In summary, the key takeaway is that trihalides yield oxyacids with three oxygen atoms, while pentahalides yield oxyacids with four oxygen atoms. This relationship can be remembered as a straightforward rule: the number of halogens in trihalides corresponds directly to the number of oxygens in the resulting oxyacids, while for pentahalides, the number of oxygens is one less than the number of halogens.

Nitrogen Family Reactions Example

In the context of chemical reactions, when dealing with trihalides, such as arsenic trifluoride (AsF₃), it is essential to recognize their ability to form oxyacids. Trihalides consist of three halogen atoms, which correspondingly lead to the formation of three oxygen atoms in the resulting oxyacid. For arsenic, a Group 5A element, the reaction can be represented as:

H₃AsO₃ + 3HF

In this equation, H₃AsO₃ represents the oxyacid formed, while HF denotes the hydrogen halide produced during the reaction. To ensure the reaction is balanced, coefficients are adjusted accordingly. In this case, placing a coefficient of 3 in front of HF balances the equation, resulting in:

H₃AsO₃ + 3HF → H₃AsF₃ + 3H₂O

Thus, the balanced equation illustrates the relationship between trihalides and the formation of oxyacids, emphasizing that three halogens yield three oxygens, leading to the creation of a stable oxyhalide compound.

Provide the products from the reaction between 2 moles of antimony with four moles of chlorine.
2 Sb(s) + 4 Cl₂ → 

• A. SbCl₃
• B. Sb₂Cl₃
• C. SbCl₅
• D. SbCl₄

Answer: (C)

Name the oxyacid created from the reaction between phosphorus trichloride and 3 moles of water.

• A. hydrophorous acid
• B. phoric acid
• C. phosphorous acid
• D. phosphoric acid

Answer: (C)

Here’s what students ask on this topic:

What are the common reactions of group 5A elements with halogens?

Group 5A elements react with halogens to form trihalides and pentahalides. Trihalides are compounds with three halogen atoms, while pentahalides have five halogen atoms. The general reaction for forming a trihalide is:

$e+3X=eX{3}_{}$

where e represents a group 5A element and X is a halogen. For pentahalides, the reaction is:

$eX{3}_{}+2X=eX{5}_{}$

Note that nitrogen, being in period 2, cannot form pentahalides due to its inability to have an expanded octet.

How do trihalides and pentahalides of group 5A elements react with water?

Trihalides and pentahalides of group 5A elements react with water to form oxyacids. Trihalides produce oxyacids with three oxygen atoms, while pentahalides yield oxyacids with four oxygen atoms. The general reaction for a trihalide with water is:

$eX{3}_{}+3H2O=H{3}_{}eO{3}_{}+3\mathrm{HX}$

For pentahalides, the reaction is:

$eX{5}_{}+4H2O=H{3}_{}eO{4}_{}+5\mathrm{HX}$

where e is a group 5A element and X is a halogen. Nitrogen's trihalides do not participate in these reactions.

Why can't nitrogen form pentahalides?

Nitrogen cannot form pentahalides because it is in period 2 of the periodic table and cannot have an expanded octet. Elements in period 2 are limited to a maximum of eight electrons in their valence shell, which restricts nitrogen to forming only trihalides. In contrast, elements from period 3 and lower can have expanded octets, allowing them to form pentahalides with five halogen atoms.

What are oxyacids, and how are they formed from group 5A elements?

Oxyacids are covalent compounds containing a hydrogen atom bonded to an oxyanion. They are formed when trihalides and pentahalides of group 5A elements react with water. Trihalides produce oxyacids with three oxygen atoms, while pentahalides yield oxyacids with four oxygen atoms. For example, a trihalide reaction with water can be represented as:

$eX{3}_{}+3H2O=H{3}_{}eO{3}_{}+3\mathrm{HX}$

where e is a group 5A element and X is a halogen. The resulting oxyacid has three oxygen atoms. For pentahalides, the reaction is similar but results in an oxyacid with four oxygen atoms.

What is the significance of expanded octets in the reactions of group 5A elements?

Expanded octets are significant in the reactions of group 5A elements because they allow elements from period 3 and lower to form compounds with more than eight electrons in their valence shell. This capability enables these elements to form pentahalides with five halogen atoms. For example, arsenic and antimony, which are metalloids in group 5A, can have expanded octets and thus form pentahalides. In contrast, nitrogen, which is in period 2, cannot have an expanded octet and is limited to forming trihalides.