Glossary
Anion
A negatively charged ion, formed when an atom gains one or more electrons.
Example:
A sulfur atom can gain two electrons to become a sulfide anion, S²⁻.
Cation
A positively charged ion, formed when an atom loses one or more electrons.
Example:
When magnesium loses two electrons, it forms the Mg²⁺ cation.
Covalent Bonds
Chemical bonds formed by the sharing of electrons between two atoms, typically between two nonmetals.
Example:
In a methane molecule (CH₄), carbon and hydrogen atoms are linked by covalent bonds where electrons are shared.
Electronegativity
A measure of an atom's ability to attract shared electrons towards itself in a chemical bond.
Example:
Oxygen has a high electronegativity, which causes it to pull electrons more strongly in a water molecule, creating a polar bond.
Full Charges
Discrete positive (+) or negative (-) charges on ions, resulting from the complete transfer of electrons in an ionic bond.
Example:
In magnesium oxide (MgO), the magnesium ion has a full positive charge (+2) and the oxide ion has a full negative charge (-2).
Ionic Bonds
Chemical bonds formed by the complete transfer of electrons from a metal atom to a nonmetal atom, resulting in the formation of oppositely charged ions that are held together by electrostatic attraction.
Example:
The strong attraction between Na⁺ and Cl⁻ ions in table salt exemplifies an ionic bond.
Ions
Atoms or molecules that have gained or lost electrons, resulting in a net positive or negative electrical charge.
Example:
When a potassium atom loses an electron, it forms a positively charged ion, K⁺, to achieve a stable electron configuration.
Metalloids
Elements that possess properties intermediate between those of metals and nonmetals, often exhibiting semiconducting behavior.
Example:
Germanium is a metalloid used in electronics for its ability to act as a semiconductor.
Metals
Elements typically found on the left side of the periodic table, characterized by good conductivity of heat and electricity, malleability, and ductility.
Example:
Aluminum is a lightweight metal commonly used in aircraft construction due to its strength and low density.
Nonmetals
Elements typically found on the right side of the periodic table, which are generally poor conductors of heat and electricity and are often brittle.
Example:
Carbon, in its graphite form, is a nonmetal that can conduct electricity, an exception to the general rule.
Nonpolar Covalent Bonds
Covalent bonds in which electrons are shared equally between two atoms, typically because they have identical or very similar electronegativities.
Example:
The bond in a diatomic hydrogen molecule (H₂) is a nonpolar covalent bond as both hydrogen atoms share electrons equally.
Octet Rule
The principle that atoms tend to gain, lose, or share electrons in order to achieve a stable electron configuration with eight valence electrons, similar to a noble gas.
Example:
Chlorine readily forms a single bond or gains an electron to satisfy the octet rule, achieving stability.
Oxidation
The process in which an atom or ion loses electrons, resulting in an increase in its oxidation state.
Example:
When a piece of zinc metal reacts with acid, the zinc atoms undergo oxidation as they lose electrons to become Zn²⁺ ions.
Partial Charges
Fractional positive (δ+) or negative (δ-) charges that develop on atoms within a polar covalent bond due to the unequal distribution of shared electrons.
Example:
In hydrogen fluoride (HF), the hydrogen atom has a partial positive charge (δ+) because fluorine attracts the shared electrons more strongly.
Polar Covalent Bonds
Covalent bonds in which electrons are shared unequally between two atoms due to a significant difference in their electronegativities.
Example:
The bond between carbon and oxygen in carbon monoxide is a polar covalent bond because oxygen pulls the shared electrons more strongly.
Reduction
The process in which an atom or ion gains electrons, resulting in a decrease in its oxidation state.
Example:
In a redox reaction, a copper(II) ion undergoes reduction when it gains two electrons to form solid copper metal.
Valence Electrons
The outermost electrons in an atom, which are primarily involved in chemical bonding.
Example:
A nitrogen atom has five valence electrons, which explains why it typically forms three bonds and has one lone pair.