Chemical Bonding Flashcards
what is an ion
a charged atom or group of atoms
what happens when an atoms loses one or more electrons
it becomes a positive ion called a cation
why do elements in group 1 form ions with a charge of +1
because they lose one electron to have a stable electron arrangement
what happens when an atom gains one or more electrons
they become a negative ion called a anion
why does the gain of an electron from an atom always produce a negative ion
there are more negative charges than positive so the atom becomes a negative ion
what is an ionic bond
the electrostatic force of attraction between the positive and the negative ions as a result of electron transfer
what is an ionic bond formed between
a metal and a non-metal
what is the structure of ionic compounds
a giant ionic lattice
how are ions held together in ionic compounds such as NaCl
the strong electrostatic attractions between the positive and negative ions hold the ions together in sold NaCl
what are the properties of ionic compounds
they have high melting/boiling points
conduct electricity when melted or dissolved in water
mostly all ionic compounds are soluble in water
solids at room temperature
why do ionic compounds have high melting/boiling points
they have a giant ionic lattice with strong electrostatic forces of attractions between the positive and negative ions. A large amount of energy is needed to break the strong ionic bonds and make the ions mobile
why do ionic compounds only conduct electricity when molten or dissolved in water
when they are melted or dissolved in water, the ions can move and carry the charge but when the compounds are solid the ions can’t move and just vibrate around their fixed positions
what is a covalent bond
a pair of electrons shared between two atoms
what is a covalent bond formed between
two non-metals
what is the structure of covalent compounds
a simple molecular strucutre
why do larger molecules have higher boiling points than smaller molecules
larger molecules have more intermolecular forces
what are the properties of covalent compounds
they have low boiling points
they don’t conduct electricity
often insoluble in water but soluble in organic solvents
why do covalent compounds have low boiling points
they have a simple molecular structure. They are made up of small molecules with weak forces between the molecules and little energy is needed to break these weak intermolecular forces
why do covalent compounds not conduct electricity
there are no free electrons as the outer electrons are all fixed in covalent bonds
why does the metal calcium form an ionic bond but the non-metal silicon forms covalent bonds
a calcium atom can lose two electrons to obtain a stable electron arrangement. Silicon cannot lose four electrons or gain four electrons but has to share four electrons
what are allotropes
different forms of an element in the same physical state
what are the allotropes of carbon
diamond, graphite, graphene and fullerene
what is the structure of diamond
giant covalent lattice with strong covalent bonds between the atoms
why does diamond have a high melting point
many bonds need to be broken to melt it and this needs a large amount of energy
why is diamond a hard substance
it has a giant covalent lattice with strong covalent bonds between atoms that extend throughout the lattice
why does diamond not conduct electricity
there are no free electrons as each carbon atom is covalently bonded to four other carbon atoms
what are the uses of diamond
jewellery, glass cutters, drill bits
what is the structure of graphite
giant covalent lattice
what are the properties of graphite
soft and slippery
conducts electricity
high melting point
why is graphite soft and slippery
graphite has layers of carbon atoms and there are weak forces between the layers so the layers can slide over each other
why does graphite conduct electricity
as each carbon atom only forms 3 bonds, each carbon atom has one free electron so graphite has delocalised electrons which move along the layers and carry the charge
why does graphite have a high melting point
graphite has a giant covalent lattice with strong covalent bonds between the atoms therefore many bonds need to be broken to melt it and this needs a large amount of energy
what are the uses of graphite
electrodes
in pencils
as a lubricant
what is the structure of graphene
giant covalent lattice with strong covalent bonds between the atoms
what are the properties of graphene
high melting points
conducts electricity
thin and light
good electrical conductor
why does graphene have a high melting point
it has a giant covalent lattice with strong covalent bonds between the atoms and many bonds need to be broken to melt it and this needs a large amount of energy
why does graphene conduct electricity
as each carbon atom only forms 3 bonds, each carbon atom has one free electron so graphene has delocalised electrons. These delocalised electrons move along the layers and carry the charge
what is the strucutre of fullerene
molecular structure
why does fullerene have a low melting point
in fullerene there are weak forces between the molecules. Little energy is needed to break these weak intermolecular forces and melt fullerene so it has a low melting point
why doesn’t fullerene conduct electricity
fullerene has delocalised electrons so it conducts electricity across the surface of the molecule however, fullerene is a poor conductor as there is no movement of electrons between the molecules
what are fullerenes used in
aircraft, space and car industires
what is graphene used in
electronics and composites
what type of bond is in metalsd
metallic bond
what is metallic bonding
the electrostatic force of attraction between the positive ions and the delocalised electrons
what is the strucutre in metals
giant metallic latitce
why are metals good conductors of electricity when solid
delocalised electrons flow through the metal structure and carry the charge
why are metals malleable
ina metal the ions are held in a lattice structure with no fixed bonds. Therefore when a metal is bent or hammered the layers of ions slide over each other allowing the metal to change its shape without breaking the structure
why do metals have a high melting point
they have a giant metallic lattice. there are strong electrostatic forces of attraction between the metal ions and the delocalised electrons and a large amount of energy is needed to break the strong attractive forces.
