SC2 - STRUCTURE AND BONDING Flashcards
atoms are more stable with __________
a full outer shell of electrons.
atoms that lose electrons (metals) gain a ________ charge
positive
atoms that gain electrons (non-metals) gain a ________ charge
negative
ionic bonds form between ______ and __________
metals and non-metals
in ionic bonds, METALS ____ electrons to form ________ ions.
LOSE electrons
form POSITIVE ions
in ionic bonds NON-METALS ____ electrons to form ________ ions
GAIN electrons
form NEGATIBE ions
describe how ionic bonds are formed
- in an ionic bond the metal ‘gives’ its electrons to the non-metals to form positive and negative ions
- the positive and negative ions attract each other
- an ionic bond is the ELECTROSTATIC ATTRACTION between a positive and negative ion
ionic compound definition
- ionic compounds consist of regular arrangements of positive and negative ions called an ionic lattice
- positive and negative ions combine in fixed ratios to give neutral compounds
properties of ionic compounds (3)
- form crystals with HIGH melting points (because of strong electrostatic forces)
- dissolve in water to give solutions (water solvates/surrounds ions)
- conduct electricity when dissolved in solution or molten but not when solid (because ions are fixed in solid but free in solution/when molten)
covalent bonds form between ____________
two NON-METALS
covalent bond definition
a pair of electrons shared between two atoms
a double covalent bond consists of _______
two shared electrons
covalent bonds are found in two types of structures: _______ and _______
- simple molecules
- giant covalent structures
describe the bonds in simple molecular compounds
- strong covalent bonds (from shared electrons) holding the atoms together in a molecule
- weak intermolecular forces between molecules which are much more easily broken
properties of simple molecular compounds
- gases and liquids with low melting and boiling points
- do not conduct electricity
describe the bonds in giant covalent structures
- every atom is joined to other atoms with a strong covalent bond
properties of giant covalent structures
- very high melting and boiling points (need to break all the strong covalent bonds)
- does not conduct electricity (no mobile charged particles)
- strong (rigid arrangement of atoms hall by covalent bonds)
- insoluble in water
carbon allotrope: diamond
bonding, properties and uses
- BONDING: giant covalent. every carbon atom bonded to 4 other carbon atoms with strong covalent bonds
- PROPERTIES: hard, strong, high melting point, doesn’t conduct electricity, doesn’t dissolve
- USES: cutting equipment
carbon allotrope: graphite
bonding, properties and uses
- BONDING: every carbon atom bonded to 3 other carbon atoms to form hexagonal layer. strong covalent bonds in the layers, weak forces of attraction between layers
- PROPERTIES: form layers which slide over each other, high melting point, conducts electricity along layers, does not dissolve
- USES: pencil lead, electrodes, lubricant
carbon allotrope: graphene
bonding, properties
a single layer of graphite.
- BONDING: every carbon atom bonded to 3 other carbon atoms to form hexagons in a single layer
- PROPERTIES: strong but flexible, high melting point, conducts electricity along sheet
carbon allotrope: C₆₀
bonding, properties
- BONDING: simple molecular. large molecule with 60 atoms, in the molecule every carbon atom is bonded to 3 other carbons with strong covalent bonds. weak intermolecular forces between molecules
- PROPERTIES: molecules are strong, low melting points
metallic bonds form between _______
metal atoms and metals from giant metallic structures
atomic structure of a metal
a regular arrangement of metal ions surrounded by a sea of delocalised electrons
properties of metals (4)
- high melting and boiling point (because of strong attraction between nucleus of atoms and delocalised electrons)
- conducts electricity (outer shell electrons free to move around carrying a charge)
- strong (layers can slide while maintaining metallic bonding)
- insoluble in water
