Question

Beryllium forms a compound with chlorine that has the empirical formula \(\mathrm{BeCl}_{2}\). How would you determine whether it is an ionic compound?

Short answer

BeCl2 might initially appear ionic due to metal and non-metal pairing, but it has covalent character due to Be's polarizing power and structure.

Step-by-step solution

Understand the Basics of Ionic Compounds

Ionic compounds are formed from a metal and a non-metal. They consist of ions held together by electrostatic forces. In this compound, Beryllium (Be) is a metal and Chlorine (Cl) is a non-metal.

Identify Type of Elements Involved

Beryllium (Be) is located in Group 2 of the periodic table, making it an alkaline earth metal. Chlorine (Cl) is located in Group 17, making it a halogen. The combination of metal and non-metal typically indicates an ionic bond.

Consider Electronegativity Difference

Ionic compounds often form when there is a large difference in electronegativity between the elements. The electronegativity of Be is 1.57 and that of Cl is 3.16. The difference in electronegativity is 3.16 - 1.57 = 1.59, which is generally consistent with ionic bonding, as it is greater than 1.7.

Check Compound Structure

In a typical ionic structure, compounds form a crystal lattice. Although BeCl2 can exist as a crystal, it does not form the classic lattice structure due to the covalent character induced by Be's high polarizing power (small size).

Evaluate Additional Chemical Properties

Consider if the compound meets additional properties of ionic compounds such as high melting and boiling points, and conductivity when liquefied or dissolved in water. BeCl2 doesn't readily fit these properties, indicating more covalent bonding.

Key concepts

Electronegativity

Electronegativity is a crucial concept in chemistry. It describes how strongly an atom can attract electrons towards itself. This property helps in predicting the type of bond that forms between two elements.

To determine the nature of the compound \(\mathrm{BeCl}_{2}\), understanding electronegativity is key. For ionic bonds, elements typically have a large difference in electronegativity. They form when the difference in electronegativity between two atoms is generally greater than 1.7.

In this exercise, beryllium (Be) has an electronegativity value of 1.57, while chlorine (Cl) has a higher value of 3.16. The difference is calculated as follows:

• Be = 1.57
• Cl = 3.16
• Difference = 3.16 - 1.57 = 1.59

This difference closes in on the typical threshold for ionic bonds, signaling some ionic characteristics, although slightly below the benchmark (1.7), which suggests \(\mathrm{BeCl}_{2}\) might not be a classic ionic compound.

Beryllium

Beryllium is a fascinating element found in Group 2 of the periodic table, known as the alkaline earth metals. These metals are typically shiny and have good electrical conductivity properties.

However, beryllium stands out for a few reasons:

• It has a relatively small atomic radius, which gives it a high polarizing power. This quality enables Be to distort electron clouds of other atoms, often inducing a covalent character in its compounds.
• As a metal, it typically donates electrons when bonding with non-metals, contributing positively to the formation of ionic compounds.
• Despite its potential to form ionic bonds, the high charge density due to its small size often results in significant covalent bonding characteristics, as observed in \(\mathrm{BeCl}_{2}\).

Understanding beryllium's unique properties is essential in predicting and explaining the partially covalent content in \(\mathrm{BeCl}_{2}\), despite its overall ionic introduction.

Chlorine

Chlorine is a highly reactive non-metal located in Group 17 of the periodic table, part of the family known as halogens. These elements are known for their strong electronegativity and their capability to form salts with metals.

Here are some fundamental aspects of chlorine relevant to this chemistry exercise:

• Chlorine has an electronegativity of 3.16, making it one of the most electronegative elements and highly effective in attracting electrons.
• In compounds like \(\mathrm{BeCl}_{2}\), chlorine generally acts as the electron acceptor, gaining electrons from metals such as beryllium.
• This property makes chlorine an essential player in forming ionic compounds. However, due to the specific conditions in \(\mathrm{BeCl}_{2}\), such as beryllium's polarizing capabilities, a degree of covalent character is also introduced.

Understanding chlorine's role helps explain both the ionic and covalent attributes found in compounds involving halogens.