Problem 7 - Biology Concepts and Applications

Question

The mutual attraction of opposite charges holds atoms together as molecules in a(n) __________ bond. a. ionic b. hydrogen c. polar covalent d. nonpolar covalent

Step-by-Step Solution

Answer

a. ionic

Step 1: Definition Review

To determine which type of bond holds atoms together as molecules due to mutual attraction of opposite charges, we must first understand what each option means. Ionic bonds involve the transfer of electrons from one atom to another, resulting in positively and negatively charged ions that attract each other. Hydrogen bonds involve attractions between a hydrogen atom and a more electronegative atom, but they aren't directly due to opposite charges. Polar covalent bonds involve unequal sharing of electrons, leading to slight charges, but not opposite. Nonpolar covalent bonds involve equal sharing of electrons, where no charges are formed.

Step 2: Identify Key Characteristics

The problem states that the bond is formed due to mutual attraction of opposite charges. This description fits ionic bonds, where one atom loses an electron and becomes positively charged, and another atom gains that electron and becomes negatively charged. These opposite charges attract each other, forming the bond.

Step 3: Elimination

Using the definitions and identified characteristics: - Ionic bonds fit as they involve opposite charges attracting. - Hydrogen bonds do not involve fully opposite charges (only partial positive and negative attractions). - Polar covalent bonds involve sharing electrons unequally, creating partial charges, not full opposite charges. - Nonpolar covalent bonds have no charges, as electrons are shared equally.

Step 4: Conclusion

From the elimination step, it is clear that the ionic bonds are the ones held together due to the attraction between opposite charges, as described in the exercise.

Key Concepts

Ionic Bond

An ionic bond is formed when one atom transfers an electron to another, creating ions. These ions are charged particles that stick together due to their opposite charges. For example, table salt ( ) is formed through an ionic bond where sodium (Na) donates an electron to chlorine (Cl), creating the ions Na^+ and Cl^-. The positively charged sodium ion is attracted to the negatively charged chloride ion, forming a stable ionic compound.

• Characterized by the transfer of electrons.
• Results in positive and negative ions.
• Held together by strong electrostatic forces.

Ionic bonds are often found in compounds formed between metals and non-metals. This bond type has high melting and boiling points due to the strong attraction between ions.

Covalent Bond

A covalent bond occurs when two atoms share one or more pairs of electrons. Instead of forming ions, atoms get even closer. Each atom contributes one electron to the bond, making it stable. Covalent bonds are fundamental to organic chemistry, forming the backbone for numerous biological molecules.

• Involves shared pairs of electrons.
• Can form single, double, or triple bonds based on the number of shared electrons.
• Creates molecules, such as H₂O or CO₂.

Covalent bonds are categorized into nonpolar and polar covalent bonds based on the equal or unequal sharing of electrons, leading to varying degrees of charge distribution.

Hydrogen Bond

Hydrogen bonds are weak attractions but play a crucial role in the structure of various compounds. They occur when a hydrogen atom is attracted to an electronegative atom such as oxygen, nitrogen, or fluorine. Despite being weak, numerous hydrogen bonds can provide significant stability to structures like DNA or proteins.

• Not a true bond, but an intermolecular force.
• Involves attractions between a partially positive hydrogen and a partially negative atom.
• Essential for maintaining the structure and function of biological molecules.

Hydrogen bonds give water its unique properties like high surface tension and boiling point, essential for life.

Electronegativity

Electronegativity is a measure of how strongly an atom can attract and hold onto electrons in a bond. It plays a crucial role in determining whether a bond will be covalent, polar covalent, or ionic. Elements with high electronegativity, like fluorine and oxygen, tend to pull electrons closer, influencing bond type.

• Fluorine is the most electronegative element.
• Higher electronegativity difference usually leads to ionic bonds.
• Smaller differences may result in polar covalent bonds.

Understanding electronegativity helps predict molecule behavior, such as polarity and reactivity in chemical reactions.