Bonding and structure

What are ions

positive ions

negative ions

charged particles cations anions

explain ionic bonding

metal and non metal react metal loses electrons forms positively charged ion non metal gains electrons form negatively charged ion. The ions are attracted to each other -electrostatic force

explain covalent

non metals bond together share electrons positive nuclei attracted to shared pair of electrons by electrostatic force so bonds strong

Ionic compound structure

Giant ionic lattices held by electrostatic attraction between oppositely charged ions in all directions of the lattice

melting boiling point ionic compounds and simple covalent?

high because of the many strong ionic bonds which need lots of energy to overcome

low because the molecules are held by weak intermolecular forces little energy needed to overcome them

ionic compounds conduct electricity when

melted then the ions are free to move and carry electrical charge

dissolved because ions separate and are free `to move and carry a charge

when solid ions held in place - lots of energy needed to overcome this

properties of simple molecular structures

gasses liquids at room temp

as molecules get bigger intermolecular forces increase so more energy needed to break them

don’t conduct electricity because they aren’t charged no free electrons or ions

limitations of the particle model

represented as solid spheres - particles are empty space not always spherical

Polymers

long chain molecules made up of many smaller intis called monomers Atoms in a polymer chain are held by strong covalent bonds

The intermolecular forces between ______ molecules are _______ than between … so more …

still weaker than ___ ___ ___ so _____

polymer larger simple covalent molecules energy need to break them ionic or covalent bonds lower boiling points

giant covalent structures

all atoms bonded to each other by strong covalent bonds

high melting and boiling points because of covalent bonds

no charged particles so don’t conduct electricity

metals are ductile and malleable because…

the rows of atoms can slide over each other because of the regular structure

alloys are stronger than metals because

the rows have been jumbled and it is no longer neatly arranged so the layers are no longer able to slide over each other

high melting and boiling points in metals because …

the strong attraction between the positive ions and the delocalised electrons - lots of energy required to break the many bonds

metal conducts heat because

heat is energy so it causes ions and electrons in the metal to vibrate more - these vibrations are conducted through the metals because of the delocalised electrons and the neat rows.

metal conducts electricity because

of the delocalised electrons, they carry charge and are able to move they carry the current through the structure

Diamond

Each carbon atom forms 4 covalent bonds in a very rigid giant covalent structure

high melting and boiling point

lots of energy needed to break covalent bonds

does not conduct electricity

Graphite

each carbon atom forms 3 covalent bonds creating layers of carbon arranged in hexagons. Each carbon atom bonded to 3 others and has one free delocalised electron that is able to move between the layers

The layers of carbon can slide over eachother because no strong covalent bonds between layers

high melting point because lots of energy needed to break bonds

can conduct electricity

silicon dioxide

similar to Dimond high melting and boiling point

graphene

one layer of graphite strong because of covalent bonds between carbon atoms can conduct because delocalised electron

light and strong

Fullerene

molecules of carbon shaped like a closed tube or hollow ball

arranged in hexagons of 5 or 7 carbon atoms

used to deliver drugs into body (from around atom or molecule)#

Buckminsterfullerene first to be discovered c60 hollow sphere

nanotubes

formed from fullerenes are tiny carbon cylinders ratio between length and diameter is very high

can conduct electricity and thermal energy

high tensile strength

used in electronics

Metallic bonding

positive metal ions are surrounded by a sea of delocalised electrons . The ions tightly packed arranged in rows

strong electrostatic force of attraction

Properties of Metals

solid because electrostatic forces are strong so lots of energy needed to break them

delocalised electrons carry charge and thermal energy so good conductors of heat and electricity

malleable because layer of atoms can slide over eachother

Pure metals

too soft

mixed with other metals to make them harder

allows

different elements have different size atoms so when new metal is mixed with pure metal the new metal will distort the layers of metal atoms making it more difficult for them to slide over eachother making it harder

graphite and diamond have ___ bonds Graphite is verry ____ because the atoms are arranged in ____ and the forces between the _____ are verry ____ so they can …

covalent soft layers layers weak slide over each other

conduct electricty Dimond graphite

Dimond no graphite yes - delocalised electrons

Diameter

Coarse particles

Fine particles

Nano particles

1-100 nm

100-2500nm

2500-10000nm

nanoparticles

high surface area to volume ratio so smaller amounts needed compared to normal sized particles

As the side of cube decreases by a factor of 10 the surface area to volume ratio increases by a factor of 10.

Uses of Nano particles

catalysts

deliver drugs

tiny electrical circuits

cosmetics- sun cream better skin coveragw

Risks of Nano Particles

not fully understood

don’t know long term impact on health

could damage cells