Chemical Bonding
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What are chemical bonds?
Electrostatic forces of attraction that exist between particles
What is electronegativity?
Electronegativity of an atom is a measure of its ability to attract electrons in a bonds
How do electronegativity generally change across a period?
Increases across a period
How do electronegativity generally change down a group?
Decreases down a group
What bonds do large difference in electronegativity form?
ionic bonds
What bonds do small or no difference in electronegativity form?
covalent bonds (electronegative) or metallic bonds (electropositive)
What are metallic bonds?
Strong electrostatic forces of attraction between a lattice of positive metal cation and a sea of delocalised mobile valence electrons
What is the structure that has metallic bonds?
Giant metallic lattice structure
What is the nature of metallic bonds?
Non-directional
What are the factors that affect the strength of metallic bonds?
• charge and ionic radius of metal cation • number of valence electrons metal atom has
How does charge and ionic radius affect the strength of metallic bonds?
• the greater the charge and the smaller the size of metal cation (greater the charge density) • stroger the electrostatic forces of attraction between metal cation and delocalised mobile valence electrons
How does the number of valence electrons affect the strength of metallic bonds?
the larger the mass of valence electrons in the metal atom, the greater the charge of the resultant metal cation and the larger the number of declocalised valence electrons contributed into the sea of delocalised mobile valence electrons
What are ionic bonds?
strong electrostatic forces of attraction between cations and anions
What structure has ionic bonds?
Giant ionic lattice structure
What is the nature of ionic bonds?
Non-directional
What is coordinate number?
The number of oppositely charged ions surrounding an ion
What can ionic bond strength be deduced from?
lattice energy of an ionic compound
What is lattice energy?
Energy released when one mole of solid ionic compound is formed from its constitutent gaseous ions under standard conditions
What affects the magnitude of lattice energy?
• charges of cation and anion • ionic radii of cation and anion
What is the formula for lattice energy?
LE ∝ |Z⁺ × Z⁻ / r⁺ + r⁻|
What are covalent bonds?
strong electrostatic forces of attraction between nuclei of each atom for the shared pair of electrons
What is separation between atoms a fine balance of?
• attraction of nuclei for shared electrons • repulsion between electrons on each atom • repulsion between positively charged nuclei of each atom
What is bond length?
distance between the nuclei of atoms involved in a covalent bond
How are covalent bonds formed?
• electrons involved are both unpaired electrons and located in higher energy orbitals • electrons are shared such that each atom will attain noble gas configuration