chemical bonding 1 Flashcards
factors affecting strength of ionic bond and defintions
- charge of ion
- radius
- lattice energy
- energy released when 1 mole of crystalline ionic solid is formed from its constituent gaseous ions
just read
q+ and q- are the same for both compounds. However, F- is smaller than Cl- and interionic distance for NaF is smaller than NaCl. Hence, NaF has a greater magnitude of LE and a stronger ionic bond
properties of ionic compounds (4)
- high bp/mp
- soluble in polar solvents but not in non polar solvents
- cannot conduct electricity in solid state as ions are held in fixed positions and cannot act as charge carriers but can in aqueous/molten state as ions are free to move to act as mobile charge carriers
- hard and brittle as a slight displacement along the cleavage plane can cause ions of like charges to move opposite one another and the strong repulsion causes the ionic crystal lattice to shatter
ionic bond
electrostatic attraction between cations and anions in an ionic lattice
giant molecular lattice
made up of atoms held together in an extensive network by covalent bonds
diamond and graphite structures
diamond:
- each C atom is bonded to 4 other C atoms in a 3d lattice by forming strong covalent bonds
- hence it is hard and rigid with a high melting point
graphite:
- each C atom is bonded to 3 other C atoms in a layered structure by forming covalent bonds
- there are weak intermolecular attraction between layers
- high melting point and layers can slide over each other
Simple molecular structure
made up of molecules attracted to each other by weak intermolecular forces
properties of simple molecular structure (3)
- low mp/bp
- soluble in non polar but not in polar solvents
- does not conduct electricity in solid/molten states but can conduct electricity in aqueous state as it can ionise in water to form ions
Giant metallic lattice
electrostatic attraction between a lattice of positive ions and delocalised electrons
describe metallic bond
metals are composed of a rigid lattice of positive ions surrounded by a sea of delocalised electrons
valence electrons are delocalised and do not belong to any particular cation but to the crystal lattice as a whole
bond is strong and non directional
factors affecting metallic bond
- charge of cations
- size of cations
these 2 affect CHARGE DENSITY, smaller cation with bigger charge will lead to greater EA
- number of valence electrons
metallic bond properties (5)
- high mp/bp
- high electrical conductivity even in solid state
- high density
- ions are closely packed - malleable and ductile
- since metallic bond is non directional, the layers of positive ions can glide over another easily without breaking the bond - good thermal conductivity
- when heated on one end, the electrons take in thermal energy → they move faster and more randomly, colliding with other electrons and passing the energy to them
octet rule
atoms tend to lose, gain or share electrons until they have 8 electrons in their valence shell
covalent bonding
electrostatic attraction between the shared pair of electrons and 2 nuclei
coordinate bond
formed when the shared pair of electrons is provided by only one of the bonding atoms