Question

Match the following descriptions with the type of bond (ionic, nonpolar covalent, covalent). (a) One or more electrons are transferred from a metal to a non- metal atom. (b) Electrons are shared equally between two atoms. (c) Electrons are shared unequally by two atoms.

Short answer

(a) Ionic, (b) Nonpolar covalent, (c) Covalent (polar).

Step-by-step solution

Identify Ionic Bonds

An ionic bond is characterized by the transfer of one or more electrons from one atom to another. Typically, a metal donates electrons to a non-metal. This results in the formation of positively and negatively charged ions that are held together by electrostatic forces. Looking at the given descriptions, (a) 'One or more electrons are transferred from a metal to a non-metal atom' matches the definition of an ionic bond.

Identify Nonpolar Covalent Bonds

A nonpolar covalent bond involves the equal sharing of electrons between two atoms. This usually occurs between atoms of the same element or between atoms with similar electronegativities. From the provided descriptions, (b) 'Electrons are shared equally between two atoms' signifies a nonpolar covalent bond.

Identify Polar Covalent Bonds

In a polar covalent bond, electrons are shared unequally between two atoms, leading to partial charges on the atoms. This typically occurs between atoms with different electronegativities. (c) 'Electrons are shared unequally by two atoms' describes a covalent bond, more specifically a polar covalent bond.

Key concepts

Ionic Bonds

Ionic bonds are a fundamental type of chemical bond where there is a transfer of electrons from one atom to another. This usually happens between metal and non-metal atoms. Here's how it works:

• The metal atom loses one or more electrons, becoming positively charged. This is called a cation.
• The non-metal atom gains these electrons, becoming negatively charged, known as an anion.
• The opposite charges of the ions attract each other. This attraction forms the ionic bond.

These bonds are generally strong due to the electrostatic forces holding the ions together. Ionic compounds often form crystalline structures, like salt crystals. A common example is sodium chloride (NaCl), where sodium donates an electron to chlorine. This kind of bond results in distinct properties, such as high melting and boiling points and the ability to conduct electricity when dissolved in water.
Understanding ionic bonds is crucial, as they are one of the most common types of bonds in inorganic compounds.

Covalent Bonds

Covalent bonds occur when two atoms share electrons to fill their outer electron shells. This type of bond is typical in organic compounds and certain inorganic molecules. Covalent bonds can be single, double, or triple depending on how many pairs of electrons are shared. When covalent bonds form:

• The shared electrons allow each atom to achieve a stable electron configuration.
• This sharing typically happens between nonmetal atoms.
• The strength of the bond depends on how many electrons are shared.

Covalent bonds are generally strong and often require significant energy to break. They form the backbone of molecules essential for life, such as DNA and proteins. Unlike ionic bonds, covalent compounds generally have lower melting and boiling points and are poor conductors of electricity. An important aspect of covalent bonds is polarity, which affects how molecules interact with each other.

Nonpolar Covalent Bonds

Nonpolar covalent bonds are a special category within covalent bonds. In these bonds, electrons are shared equally between the two atoms involved. This usually happens when the electronegativities of the atoms are identical or very similar. The equally shared electrons mean there is no charge separation across the bond. Here are some key points:

• Nonpolar covalent bonds often occur between atoms of the same element, like two hydrogen atoms (H₂).
• These bonds create molecules that are typically not reactive with water, as there is no charge for water molecules to interact with.
• They are important in biological systems and materials like oils and fats.

Unlike polar covalent bonds where there's a difference in electronegativity leading to a charge difference, nonpolar bonds are crucial for maintaining neutrality. This quality makes them biologically essential for maintaining cell membranes and other structures where water repellency is needed.