chem bonding and structure (eya) Flashcards
what is electronegativity
a measure of an atom’s ability to attract the electrons in a covalent bond to itself
how does electronegativity affect bonding
high electronegativity difference forms ionic bonds (metals have low electronegativity)
low electronegativity difference forms covalent bonds (non-metals have high electronegativity)
more electronegative atom acquires a partial _______
less electronegative atom acquires a partial _____
negative charge; positive charge
how do dipole moments work
show the movement of an electron cloud toward the more electronegative atom (because it attracts the electrons toward itself)
how to identify a polar compound
- electronegativity difference ≥0.5
- dipole moment arrows do not cancel each other out
why dont noble gases have electronegativity
they are inert and have no tendency to gain or share electrons
definition of ionic bonding
the strong electrostatic forces of attraction between oppositely charged ions
definition of covalent bonding
strong electrostatic forces of attraction between a shared pair of electrons and the nuclei of both atoms
definition of metallic bonding
strong electrostatic forces of attraction between positively charged ions and the ‘sea’ of delocalised electrons
why do metals have free electrons
due to close packing of metal atoms, they ‘lose’ their valence electrons to become positively charged ions. electrons no longer belong to a particular metal atom and are said to be delocalised
what is an alloy
a mixture of a metal with one or more other elements
types of bonding structures
ionic bonding: giant ionic lattice structure
covalent bonding: simple molecular structure; giant covalent structure; macromolecular structure
metallic bonding: giant metallic lattice structure
physical properties
hardness, solubility, electrical conductivity, melting and boiling point
hardness of giant ionic lattice structures
hard: strong electrostatic forces of attraction between oppositely charged ions causes ions to resist motion and be resistant to deforming
brittle: when a strong enough force is applied, ions are displaced from their lattice positions. when ions of the same charge from adjacent layers face each other, strong repulsive forces between them causes lattice structure to cleave evenly
hardness of simple molecular structures
soft: only a small amount of force is required to overcome weak intermolecular forces of attraction
hardness of giant covalent structures
diamond, silicon dioxide — hard: large amount of force is needed to break the numerous covalent bonds between atoms present throughout the entire structure
graphite — soft: layers of carbon atoms are held loosely by intermolecular forces of attraction, little force is needed to overcome them
hardness of giant metallic lattice structures
malleable and ductile: when sufficient force is applied, layers of ions can slide over one another easily without disrupting metallic bonding
definition of malleability and ductility
ability of a metal to be hammered into thin sheets; ability of a metal to be drawn into a thin wire
hardness of alloys
not malleable and ductile: different sizes of atoms present disrupt the regular lattice arrangement, hence layers of atoms cannot slide over one another easily
types of solvents
aqueous solvents; organic solvents
aqueous solvents vs organic solvents
aqueous solvents: water-based, used to dissolve polar substances
organic solvents: carbon-based, used to dissolve non-polar substances
solubility of giant ionic lattice structures
soluble in aqueous solvents, insoluble in organic solvents
solubility of simple molecular structures
insoluble in aqueous solvents (EXCEPT iodine, sugar, hcl, ammonia etc), soluble in organic solvents
solubility of giant molecular structures
insoluble in both aqueous and organic solvents
solubility of macromolecular structures
insoluble in aqueous solvents
MAY be soluble in organic solvents
solubility of giant metallic lattice structures
insoluble in aqueous and organic solvents
electrical conductivity of giant ionic lattice structures
conduct electricity in aqueous state: ionic compounds dissolve in water and dissociate to form mobile ions that can conduct electricity
conduct electricity in molten state: large amount of energy can overcome strong electrostatic forces of attraction between oppositely charged ions, making them mobile
electrical conductivity of simple molecular structures
do not conduct electricity: no mobile charge carriers to conduct electricity
electrical conductivity of giant covalent structures
normal — do not conduct electricity: no mobile charge carriers to conduct electricity
graphite — can conduct electricity: 1 unbonded valence electron per carbon atom that is mobile within the layer to conduct electricity
electrical conductivity of macromolecular structures
do not conduct electricity: no mobile charge carriers to conduct electricity
electrical conductivity of giant metallic lattice structures
conduct electricity in solid and molten states: mobile electrons present to conduct electricity
electrical conductivity of alloys
conduct electricity: presence of sea of delocalised electrons to act as mobile charge carriers
melting and boiling points of giant ionic lattice structures
high melting and boiling points: large amount of energy required to overcome the strong electrostatic forces of attraction between oppositely charged ions
melting and boiling points of simple molecular structure
low melting and boiling point: small amount of energy required to overcome weak intermolecular forces of attraction between molecules
melting and boiling points of giant molecular structures
high melting and boiling points: large amount of energy required to overcome the strong covalent bonds between atoms present throughout the structure
melting and boiling points of macromolecules
low melting and boiling points: small amount of energy required to overcome weak intermolecular forces of attraction between molecules
melting and boiling points of giant metallic lattice structures
high melting and boiling points: large amount of energy required to overcome strong electrostatic forces of attraction between positive ions and ‘sea’ of delocalised electrons
melting and boiling points of alloys
high but not as high as ionic compounds: presence of other elements act as impurities that lower the melting and boiling points compared to a pure metal
different sizes of atoms in an alloy disrupt the regular arrangement of atoms, making bonds between them weaker which lowers melting and boiling points.
