Chemical Bonds and Ionic Compounds Quiz

Chemical Bonds

• Elements are typically found in compounds, not by themselves
• A compound is a substance composed of different elements (a mixture)
• Bonds are a persistent attraction between two or more atoms
• Ionic bonds: Electrostatic forces between oppositely charged ions (crystalline)
• Covalent bonds: Sharing of electrons
• Like charges repel, opposite charges attract

Ionic Bonds

• Ions are charged (+ or -)
• Ions attract each other (Coulomb's Law)
• Atoms gain or lose electrons to achieve a full valence shell
• Stable ionic structures form when charges balance
• Ionic crystals: Regular arrangements of atoms held together by attraction between ion pairs
• Properties: hard, brittle, crystalline, high melting point
• Exist as crystals
• Simple ions: Single atoms that have become charged
• Naming ionic compounds: Write the metal first, then the non-metal, and change the non-metal ending to "ide" (e.g., sodium chloride).

Ratios

• Compounds must be electrically neutral overall
• Balancing ratios neutralize the compound
• Example: Calcium fluoride (CaF₂) needs two fluoride ions to balance the positive charge of one calcium ion.
• Ionic compounds are stable only when neutral (zero-sum rule).

Polyatomic Ions

• Polyatomic ions are ions comprised of multiple atoms acting as a single ion
• Atoms are covalently bonded within the ion
• Naming compounds with polyatomic ions: Polyatomic ions are written as a group behind the positive ion

Multivalent Ions

• Some ions have varying charges (multivalent). Their charges are indicated with Roman numerals using parentheses (e.g, iron (II), iron (III)).
• Multivalent atoms are often transition metals.
• Use roman numerals in parenthesis when naming.

Covalent Bonds

• Covalent bonds are formed by nonmetals
• Covalent compounds form molecules
• Molecules make up larger structures
• Sharing electrons enables atoms to achieve a full outer shell
• Lewis dot diagrams: Show the arrangement of valence electrons
• Naming covalent compounds: Written left to right based on position on the periodic table. Prefixes indicate the number of atoms of each type in the molecule.

Diatomic Elements

• Some elements exist in nature as single bonded pairs (diatomic elements)

Video: Chemical Bonds

• Metals usually have 1-3 valence electrons; nonmetals usually have 4-8 valence electrons
• Ionic bonds have high melting points because a lot of energy is needed to break them apart
• Covalent bonds also require energy to break apart
• Covalent compounds come in three forms:
  • Simple covalent: weak intermolecular forces, low boiling points.
  • Giant covalent: Strong intermolecular forces, high boiling points
  • Polymers: Complex long chains connecting similar units.

Other Information

• Electrolytes: Compounds that conduct electricity
• Ionic compounds separate into ions in water, a process called dissociation
• Covalent compounds do not conduct electricity because they aren't charged
• Molecular shape: 3D arrangement of atoms to show molecules

Polarity and Electronegativity

• Polarity: How unevenly electrons are distributed in a covalent bond
• Polar covalent bond: Uneven electron sharing
• Non-polar covalent bond: Even electron sharing
• Electronegativity: Atoms' ability to attract electrons in a bond
• A high electronegativity difference between atoms indicates a polar bond; a low electronegativity difference between atoms indicates a non-polar bond.

Difference in Ionic and Covalent Compounds

• Ionic bonds form crystalline solids; high melting and boiling points, hard, soluble in water. Conducts electricity when dissolved or is a liquid; no odor, definite shape, not crushable, strong interparticle attractions.
• Covalent bonds form gases, solids, and liquids; low melting and boiling points; soft, some soluble in water, some not; poor electrical conductors, often odor-bearing + definite shape, crushable, weak interparticle attractions

Covalent: Polar vs Non-polar

• Polar covalent bonds: The electronegativity difference is greater than 0.4- 0.5, electrons are unequally shared
• Non-polar covalent bonds: The electronegativity difference is smaller than 0.4 -0.5, Electrons are shared equally.

Test your knowledge on chemical bonds, especially ionic bonds and their properties. This quiz covers the basics of compounds, how ions interact, and the rules for naming ionic compounds. See how well you understand the fundamental concepts of chemistry.