Bonding and structure Flashcards
what are ions
charged particles
what kind of ion do non metals make
gain electrons so negative ions
why are ions formed
the atom is trying to get a full outer shell of electrons
what is the relation between group number and the ion formed by those atoms
all produce ions with the same charge
what is ionic bonding
metals react with non metals, metals loses an electron and non metals gain one. This causes atoms to have opposite charges so they are strongly attracted to one another. this holds the ions together in an ionic compound
how do you represent the charge of an ion in a dot and cross diagram
e.g 1+ or 3+ in the top corner outside the bracket
ionic compounds have a structure called what
giant ionic lattice
pros and cons of dot and cross diagrams
good for showing how ionic compounds are formed
dont show structure of compound, relative sizes or how they are arranged
pros and cons of 3d models
show relative sizes of ions and the pattern in an ionic crystal.
only let you see outer layer of compound
pros and cons of ball and stick models
show regular pattern, show how ions are arranged, suggest crystal extends beyond what is shown, show relative sizes
sometimes ions are not shown to scale and they suggest gaps are between the ions
what is the boiling points like for ionic compounds
high
what is the solubility like of ionic compounds
most easily dissolve in water
what is the electrical conductivity of ionic compounds like
don’t conduct when solid because ions are held in fixed positions
do when melted or dissolved because then ions are free to move
what is covalent bonding
a pair of electrons is shared between 2 atoms to get full outer shells.
why are covalent bonds strong
positively charges nuclei is attracted to shared electrons by electrostatic forces
what atoms use covalent bonds
non metals
pros and cons of displayed formula
shows how atoms are connected in large molecules
dont show 3d structure or which atoms the electrons in the covalent bond have some from
what are simple molecules
a few atoms joined by covalent bonds.
what is the bonding of hydrogen
one shell with one electron in it so a single covalent bond
what is the bonding of chlorine
two chlorine atoms share one electron
what is the bonding in hydrogen chloride
2 atoms share one electron. so single covalent bond
what is the bonding in methane
carbon has 4 outer electrons so it has 4 single covalent bonds with 4 hydrogen atoms
what is the bonding in water
oxygen has 6 outer electrons so bonds to 2 hydrogen atoms
what is the bonding in nitrogen
nitrogen has 5 electrons in outer shell so 2 nitrogen atoms share 3 pairs of electrons, making a triple bond
what is the electrical conductivity of simple molecules
dont conduct. no ions or free electrons
what is the melting/ boiling point like of simple molecules
low so mostly gasses or liquids at room temperature. because the intermolecular forces are very weak, and these are the ones that have to be overcome to melt or boil.
what is a trend in melting and boiling points of simple molecules
as they get bigger, intermolecular forces increase so more energy is needed to break them.
what is a polymer
consist of lots of long molecules made of repeating sections, joined by covalent bonds and formed when lots of small units link together.
what is the shortest repeating section of a polymer called
repeating unit
how do you write down the molecular formula of a polymer
write down formula of reaping unit, put in a bracket and write a little n in the bottom corner
what are the melting points of polymers like
higher than simple covalent structures because the intermolecular forces increase as the molecules get bigger. still weaker than than ionic or covalent bonds
what are macromolecules
giant covalent structures e.g diamond and graphite. to melt you have to overcome the covalent bonds between the atoms so they have high melting points.
what is the structure of diamond and properties
each carbon atom have 4 bonds with other carbon atoms, forming a ridged structure. Does not conduct electricity
what is the structure and properties of graphite
each carbon atom has 3 covalent bonds
arranged in hexagons
no covalent bonds between the layers- held together by week intermolecular forces so free to move over each other
so soft and slippery- ideal lubricating material
high melting point as covalent bonds need a lot of energy to break
each carbon atom has one delocalized electron so conducts electricity
what is graphene
a sheet of carbon atoms joined together in hexagons. basically a single layer of graphite
what are the properties of graphene and what are they used for
very strong
very light so added to composite materials to improve strength without adding weight
can conduct electricity so can be used in electronics
what are fullerenes
hollow molecules of carbon shaped like tubes or balls. usually in hexagons, pentagons and heptagons
what are nanotubes
fullerenes which are tiny carbon cylinders, good conductors of heat and electricity
how are fullerenes used in medicine
cage other molecules so can deliver a drug to where its needed in the body in a highly controlled way
how are fullerenes used as a catalyst
huge surface area to increase ror
how are fullerenes used as lubricants
coating machine parts reduces friction
how are fullerenes used to strengthen materials
nanotubes have high tensile strength
how does metallic bonding work
electrons in outer shell of metal are delocalized. there is a strong force of attraction between negative charge of electrons and positive charge of the ions which holds metal together in a giant structure.
why are metals malleable
atoms are held together in a regular structure so the atoms form layers that are able to slide over one another
why are alloys stronger than metals
different elements have different sized atoms so when they are mixed it will distort the layers.
what is brass an alloy of
copper + zinc
