Glossary
Attraction (in PE diagrams)
The decrease in potential energy that occurs as atoms approach each other, primarily due to the electrostatic forces between the nucleus of one atom and the electrons of another.
Example:
The initial dip in the potential energy curve as atoms approach signifies the attraction between their nuclei and electron clouds, leading to bond formation.
Bond Energy
The amount of energy required to break one mole of a specific type of bond in the gaseous state, indicating the strength of the bond.
Example:
Breaking the strong triple bond in nitrogen gas (N₂) requires a very high bond energy, which is why N₂ is relatively unreactive.
Bond Length
The average distance between the nuclei of two bonded atoms in a molecule.
Example:
The bond length of a carbon-carbon single bond is longer than that of a carbon-carbon double bond, reflecting the number of shared electrons.
Bond Order
The number of chemical bonds between a pair of atoms, typically represented as single (1), double (2), or triple (3) bonds.
Example:
In carbon dioxide (CO₂), each carbon-oxygen bond has a bond order of two, indicating a double bond.
Bond Strength
A measure of how strongly two atoms are held together in a chemical bond, directly related to the bond energy.
Example:
A diamond's incredible hardness is due to the very high bond strength of the carbon-carbon covalent bonds within its structure.
Charge Magnitude (in Coulomb's Law)
The absolute value of the electrical charge on an ion, which directly influences the strength of the electrostatic attraction or repulsion between ions.
Example:
A calcium ion (Ca²⁺) has a greater charge magnitude than a potassium ion (K⁺), leading to stronger ionic interactions with an anion of the same charge.
Coulomb's Law
A fundamental law describing the electrostatic force between two charged particles, stating that the force is directly proportional to the product of their charges and inversely proportional to the square of the distance between them.
Example:
Coulomb's Law explains why a crystal of magnesium oxide (Mg²⁺O²⁻) has a much higher melting point than sodium chloride (Na⁺Cl⁻), due to the greater charges on its ions.
Covalent bonds
Chemical bonds formed by the sharing of electrons between two atoms.
Example:
In methane (CH₄), carbon and hydrogen atoms are held together by covalent bonds, where they share electrons to achieve stability.
Distance (in Coulomb's Law)
The separation between the centers of two charged particles, which inversely affects the strength of the electrostatic force between them.
Example:
As the distance between two oppositely charged ions decreases, the attractive force between them increases significantly, leading to a stronger ionic bond.
Equilibrium Bond Length
The specific internuclear distance between two bonded atoms where the potential energy of the system is at its lowest, representing the most stable bond.
Example:
For a diatomic molecule like O₂, the equilibrium bond length is the precise distance between the two oxygen nuclei where the attractive and repulsive forces are perfectly balanced, leading to maximum stability.
Intermolecular forces
Forces that exist *between* molecules, influencing physical properties like boiling point and vapor pressure.
Example:
The forces that cause water molecules to stick together and form a liquid, rather than being a gas at room temperature, are intermolecular forces.
Intramolecular forces
Forces that hold atoms *within* a molecule together, forming the chemical bonds.
Example:
The strong forces holding hydrogen and oxygen atoms together to form a water molecule (H₂O) are intramolecular forces.
Ionic bonds
Chemical bonds formed by the electrostatic attraction between oppositely charged ions, resulting from the transfer of electrons between atoms.
Example:
Sodium chloride (NaCl) forms through an ionic bond when sodium transfers an electron to chlorine, creating Na⁺ and Cl⁻ ions that attract each other.
Potential energy
The energy an object possesses due to its position or arrangement, which atoms seek to minimize for stability in bonding.
Example:
When two atoms are far apart, their potential energy is high, but as they approach and form a stable bond, their potential energy decreases to a minimum.
Repulsion (in PE diagrams)
The increase in potential energy that occurs when atoms get too close, primarily due to the electrostatic forces between their electron clouds and nuclei.
Example:
If you try to push two magnets together with like poles facing, you feel a strong repulsion, similar to how electron clouds repel when atoms are too close in a bond.