Chemical Bonding
Grade 10 · Science · Study Guide
Understand how atoms join together through ionic, covalent, and metallic bonds to form compounds and materials.
Chemical bonding occurs when atoms interact to achieve a more stable electron configuration, typically resembling the nearest noble gas. The three major bond types — ionic, covalent, and metallic — differ in how electrons are transferred or shared between atoms.
Ionic bonds form between metals and nonmetals. The metal atom loses one or more electrons to become a positively charged cation, while the nonmetal gains electrons to become a negatively charged anion. The resulting electrostatic attraction holds the ions together in a crystal lattice. Table salt (NaCl) is a classic example. Covalent bonds form when two nonmetals share electron pairs. If shared equally, the bond is nonpolar covalent; if shared unequally (due to electronegativity differences), it is polar covalent. Water (H₂O) has polar covalent bonds, giving it unique properties like surface tension and high boiling point.
Metallic bonds exist in solid metals, where freely moving electrons (an 'electron sea') are shared among positively charged metal ions. This explains why metals conduct electricity and heat, are malleable, and have a characteristic luster. Lewis dot structures are a useful shorthand for representing valence electrons and predicting how atoms will bond.
| Property | Ionic | Covalent | Metallic |
|---|---|---|---|
| Electron behavior | Transferred | Shared | Delocalized sea |
| Between | Metal + Nonmetal | Nonmetal + Nonmetal | Metal + Metal |
| Conductivity | When dissolved/molten | Generally poor | Excellent |
| Melting point | High | Variable | Variable (generally high) |
| Example | NaCl | H₂O | Cu (copper) |
Key terms
- Ionic bond
- Bond formed by electrostatic attraction between oppositely charged ions after electron transfer.
- Covalent bond
- Bond formed by the sharing of electron pairs between nonmetal atoms.
- Metallic bond
- Bond in metals where valence electrons are delocalized and shared among many ions.
- Electronegativity difference
- Determines bond type: >1.7 = ionic, 0.4–1.7 = polar covalent, <0.4 = nonpolar covalent.
- Lewis dot structure
- Diagram showing an element's symbol surrounded by dots representing valence electrons.
- Octet rule
- Atoms tend to form bonds until they have 8 electrons in their outermost shell, achieving stability.
Flashcards
- Cation
- A positively charged ion formed when an atom loses electrons.
- Anion
- A negatively charged ion formed when an atom gains electrons.
- Polar covalent bond
- A covalent bond where electrons are shared unequally due to electronegativity differences.
- Nonpolar covalent bond
- A covalent bond where electrons are shared equally between identical or similar atoms.
- Crystal lattice
- The regular, repeating arrangement of ions in an ionic compound.
- Electron sea model
- Model of metallic bonding where free electrons move throughout a lattice of positive metal ions.
Practice questions
Which type of bond forms between sodium (Na) and chlorine (Cl)?
- Covalent
- Metallic
- Ionic
- Hydrogen
Show answer
Answer: Ionic
Na (a metal) transfers its single valence electron to Cl (a nonmetal), forming Na⁺ and Cl⁻ ions held together by electrostatic attraction.
In a covalent bond, one atom completely transfers its electrons to another.
Show answer
Answer: False
In a covalent bond, electrons are shared between atoms — not transferred. Electron transfer describes ionic bonding.
The ___ rule states that atoms tend to gain, lose, or share electrons to achieve 8 valence electrons.
Show answer
Answer: octet
The octet rule describes the tendency of atoms to achieve 8 valence electrons (like noble gases) through bonding.
Which property is best explained by the metallic bonding model?
- High melting point of NaCl
- Electrical conductivity of copper
- Polarity of water
- Hardness of diamond
Show answer
Answer: Electrical conductivity of copper
In metallic bonding, delocalized electrons flow freely, allowing metals like copper to conduct electricity and heat.
A polar covalent bond forms when two atoms with very different electronegativities share electrons unequally.
Show answer
Answer: True
When electronegativity differs significantly (but not enough to fully transfer electrons), the more electronegative atom pulls the shared electrons closer, creating a polar covalent bond.
Fun facts
- Diamond is the hardest natural substance on Earth because every carbon atom is covalently bonded to four others in a rigid 3D network.
- The 'electron sea' model explains why you can flatten metal with a hammer — the ions can slide past each other while the electron sea adjusts.
- Gecko feet stick to walls using weak intermolecular forces (van der Waals), not suction — they have millions of tiny hair-like structures.
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