Problem 100 - Chemistry Matter and Change

Question

Antimony and chlorine can form antimony trichloride or antimony pentachloride. Explain how these two elements can form two different compounds.

Step-by-Step Solution

Answer

In conclusion, antimony and chlorine can form two different compounds, antimony trichloride (SbCl₃) and antimony pentachloride (SbCl₅), by sharing valence electrons in different ways to achieve stable electron configurations. Antimony can either share 3 electrons in SbCl₃ or all 5 electrons in SbCl₅, with each chlorine atom contributing one electron. Consequently, molecules with varying numbers of covalent bonds are formed between antimony and chlorine atoms.

Step 1: Valence Electrons of Antimony and Chlorine

First, we need to determine the valence electrons of both antimony (Sb) and chlorine (Cl). Antimony is a metalloid in group 15 of the periodic table and has 5 valence electrons. Chlorine is a halogen in group 17 and has 7 valence electrons.

Step 2: Formation of Covalent Bonds

Covalent bonds are formed when two non-metal atoms share electrons to achieve a full outer electron shell. In this case, antimony and chlorine will form covalent bonds to fill their outer electron shells.

Step 3: Formation of Antimony Trichloride (SbCl₃)

In the first compound, antimony trichloride (SbCl₃), antimony shares 3 of its 5 valence electrons with 3 separate chlorine atoms. Each chlorine atom contributes one electron, which means that both antimony and chlorine achieve a stable electron configuration: - Antimony: 5 valence electrons (original) + 3 shared electrons = 8 electrons (full outer shell) - Each Chlorine: 7 valence electrons (original) + 1 shared electron = 8 electrons (full outer shell) This results in the formation of SbCl₃, where each chlorine atom forms a covalent bond with the antimony atom.

Step 4: Formation of Antimony Pentachloride (SbCl₅)

In the second compound, antimony pentachloride (SbCl₅), antimony uses all 5 of its valence electrons to form covalent bonds with 5 chlorine atoms. Each chlorine atom contributes one electron, and both elements achieve a stable electron configuration: - Antimony: 5 valence electrons (original) + 5 shared electrons = 10 electrons (including its empty d-orbital) - Each Chlorine: 7 valence electrons (original) + 1 shared electron = 8 electrons (full outer shell) This results in the formation of SbCl₅, where each of the 5 chlorine atoms forms a covalent bond with the antimony atom. In conclusion, antimony and chlorine can form two different compounds, antimony trichloride (SbCl₃) and antimony pentachloride (SbCl₅), due to the different ways antimony can share its valence electrons with chlorine atoms to achieve stable electron configurations. This leads to the formation of molecules with varying numbers of covalent bonds between the elements.

Key Concepts

Valence Electrons

Valence electrons are the electrons present in the outermost shell of an atom. These electrons play a crucial role in forming bonds between atoms, particularly covalent bonds.

• For antimony (Sb), which is found in group 15 of the periodic table, there are 5 valence electrons.
• Chlorine (Cl), located in group 17, has 7 valence electrons.

The number of valence electrons determines how an atom interacts with others. Atoms tend to form bonds to achieve a more stable electron configuration, typically aiming for the same number of electrons as the nearest noble gas.
Antimony, with its 5 valence electrons, can share these electrons in different ways with chlorine, leading to the formation of distinct compounds.

Antimony Trichloride

Antimony trichloride, chemical formula SbCl₃, is one of the compounds formed by antimony and chlorine. In this compound, antimony shares electrons with three chlorine atoms, forming covalent bonds.
The formation process involves antimony sharing three out of its five valence electrons:

• Each chlorine atom contributes one electron, which pairs with one of the antimony’s valence electrons.
• This electron sharing results in each atom achieving a stable electron configuration.
• Antimony ends up with a full outer shell comprising eight electrons.
• Each chlorine atom also obtains eight electrons in its outer shell, forming a full octet.

The result is a stable molecule where the central antimony atom is linked to three chlorine atoms, making SbCl₃ a distinct compound with specific properties.

Antimony Pentachloride

Another compound formed by antimony and chlorine is antimony pentachloride, with the formula SbCl₅. In this compound, antimony utilizes all five of its valence electrons to create covalent bonds with five chlorine atoms.
This occurs through the following mechanism:

• Antimony provides each of its five valence electrons, sharing one with each of the five chlorine atoms.
• Each chlorine atom contributes one electron, completing their outer shell with eight electrons.
• Antimony expands its coordination number by using empty d-orbitals to accommodate more electrons, which allows it to have ten electrons surrounding it.

SbCl₅ results in a stable molecular formation where antimony is centrally bonded to five chlorine atoms. This difference in the sharing of electrons compared to SbCl₃ demonstrates how the same elements can form different compounds.

Electron Configurations

Electron configuration describes the distribution of electrons in an atom's orbitals. Understanding electron configurations helps explain an element's chemical properties and its tendency to form certain types of bonds.
In antimony and chlorine, the electron configurations influence how they bond:

• Antimony's electron configuration allows for a certain flexibility. While its ground state is \[ [Kr] 4d^{10} 5s^{2} 5p^{3} \], it can utilize d-orbitals when forming compounds like SbCl₅, enabling it to expand its valence shell.
• Chlorine, with a configuration of \[ [Ne] 3s^{2} 3p^{5} \], always seeks to gain one more electron to achieve a stable octet, guiding it towards forming covalent bonds with antimony.

These configurations underline the possible bonding scenarios between antimony and chlorine, resulting in the formation of either SbCl₃ or SbCl₅. Hence, electron configurations are foundational to understanding chemical reactivity and compound formation.