principles of chemistry

calculations

periodic table

ionic bonding

metallic bonding

electrolysis

arrangement

Elements​ ​are​ ​arranged​ ​in​ ​order​ ​of​ ​atomic​ ​(proton)​ ​number​ ​(bottom​ ​number)​ ​and so​ ​that​ ​elements​ ​with​ ​similar​ ​properties​ ​are​ ​in​ ​columns,​ ​known​ ​as​ ​groups.

Elements​ ​in​ ​the​ ​same​ ​periodic​ ​group​ ​have​ ​the​ ​same​ ​amount​ ​of​ ​electrons​ ​in​ ​their outer​ ​shell,​ ​which​ ​gives​ ​them​ ​similar​ ​chemical​ ​properties.

elements​ ​with​ ​the​ ​same​ ​number​ ​of​ ​shells​ ​of​ ​electrons​ ​are​ ​arranged​ ​in​ ​rows called​ ​periods

electron configuration

the​ ​electronic​ ​configuration​ ​of​ ​an​ ​element​ ​tells​ ​you​ ​how​ ​many​ ​electrons​ ​are​ ​in each​ ​shell​ ​around​ ​an​ ​electron’s​ ​nucleus

for​ ​example,​ ​sodium​ ​has​ ​11​ ​electrons:​ ​2​ ​in​ ​its​ ​most​ ​inner​ ​shell,​ ​then​ ​8,​ ​then​ ​1​ ​in its​ ​outermost​ ​shell.

remember-​ ​electrons​ ​fill​ ​the​ ​shells​ ​closer​ ​to​ ​the​ ​nucleus​ ​before​ ​filling​ ​any​ ​further out.​ ​1st​ ​shell​ ​holds​ ​2​ ​electrons,​ ​2nd​ ​and​ ​3rd​ ​hold​ ​8

metals or non-metals

Metals​ ​are​ ​generally​ ​conductive​ ​(of​ ​electricity)

Non​ ​metals​ ​(excluding​ ​graphite)​ ​are​ ​not​ ​conductive

If​ ​an​ ​element​ ​is​ ​conductive​ ​and​ ​its​ ​oxide​ ​is​ ​basic​ ​then​ ​the​ ​element​ ​is​ ​a​ ​metal

If​ ​an​ ​element​ ​is​ ​not​ ​conductive​ ​and​ ​its​ ​oxide​ ​is​ ​acidic​ ​then​ ​it’s​ ​a​ ​non​ ​metal

positions on periodic table

Metals​ ​=​ ​elements​ ​that​ ​react​ ​to​ ​form​ ​positive​ ​ions.

Majority​ ​of​ ​elements​ ​are​ ​metals.

Found​ ​to​ ​the​ ​left​ ​and​ ​towards​ ​the​ ​bottom​ ​of​ ​the​ ​periodic​ ​table.

Non-metals​ ​=​ ​elements​ ​that​ ​do​ ​not​ ​form​ ​positive​ ​ions.

Found​ ​towards​ ​the​ ​right​ ​and​ ​top​ ​of​ ​the​ ​periodic​ ​table

group vs period

group​ ​number:​ ​gives​ ​number​ ​of​ ​electrons​ ​in​ ​outer​ ​shell​ ​e.g.​ ​group​ ​3​ ​has​ ​3 electrons​ ​in​ ​outer​ ​shell

period​ ​number:​ ​gives​ ​number​ ​of​ ​electron​ ​shells​ ​e.g.​ ​period​ ​1​ ​has​ ​1​ ​shell​ ​of electrons

noble gases

They​ ​have​ ​8​ ​electrons​ ​in​ ​their​ ​outer​ ​shell​ ​(except helium,​ ​which​ ​has​ ​2).

They​ ​are​ ​unreactive​ ​and​ ​do​ ​not​ ​easily​ ​form​ ​molecules, because​ ​they​ ​have​ ​a​ ​stable​ ​arrangement​ ​of​ ​electrons.

properties based on groups

number​ ​of​ ​electrons​ ​in​ ​outer​ ​shell​ ​is​ ​responsible​ ​for​ ​the​ ​way​ ​different​ ​elements react

this​ ​means​ ​elements​ ​with​ ​the​ ​same​ ​number​ ​of​ ​electrons​ ​in​ ​the​ ​outer​ ​shell​ ​will undergo​ ​similar​ ​reactions

therefore​ ​elements​ ​in​ ​the​ ​same​ ​group​ ​have​ ​similar​ ​chemical​ ​properties

ions to know

group 1 → +1

group 2 → +2

group 3 → +3

group 5 → -3

group 6 → -2

group 7 → -1

Ag+

Cu2+

Fe2+

Fe3+

Pb2+

Zn2+

hydrogen → H+

hydroxide → OH-

ammonium → NH4+

carbonate CO32-

nitrate NO3-

sulfate SO42-

compounds have no overall charge, therefore charges of ions must cancel out

dot and cross diagrams

onic compounds are formed when a metal and nonmetal react

Ionic bonds are formed by the transfer of electrons from the outer shell of the metal to the outer shell of the non-metal

The metal therefore forms a positive ion and the non-metal forms a negative ion

electrostatic attractions

A giant structure of ions = ionic compound

Held together by strong electrostatic forces of attraction between oppositely charged ions

he forces act in all directions in the lattice, and this is called ionic bonding.

why do they have high melting and boiling points

Strong electrostatic forces of attraction between oppositely charged ions

Requires a lot of energy to overcome these forces of attraction

Therefore, the compounds have high melting and boiling points

conductivity

As a solid, the ions are in fixed positions so can’t conduct electricity

when molten or in aqueous solution the ions are free to move carrying charge
and conducting electricity

formation of ions

Ions​ ​– Atoms that have lost or gained electron/electrons.

Metal reacting with a non-metal: electrons in the outer shell of the metal atom are transferred

Metal atoms lose electrons to become positively charged ions

Non-metal atoms gain electrons to become negatively charged ions

Cation = positive ion (+ → ca+ion)

Anion = negative ion (Negative → aNion)


Percentage​ ​yield​ ​=​ ​​​​​​​​​​​​​​​​(Amount​ ​of ​​product ​​produced​​​​ ​​​​​​​​​​​​​​​​​​​​​​​​​​​​​x​​ 100)/ ​​​​​​​​​ ​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​ Maximum​​ amount ​​of​ ​product ​​possible

reacting masses

Chemical​ ​equations​ ​can​ ​be​ ​interpreted​ ​in​ ​terms​ ​of​ ​moles

Masses​ ​of​ ​reactants​ ​&​ ​products​ ​can​ ​be​ ​calculated​ ​from​ ​balanced​ ​symbol
equations.​ ​If​ ​you​ ​are​ ​given​ ​the​ ​reacting​ ​mass​ ​of​ ​one​ ​reactant​ ​and​ ​asked​ ​to​ ​find the​ ​mass​ ​of​ ​one​ ​product​ ​formed:

Find​ ​moles​ ​of​ ​that​ ​one​ ​substance:​ ​moles​ ​=​ ​mass​ ​/molar​ ​mass

Use​ ​balancing​ ​numbers​ ​to​ ​find​ ​the​ ​moles​ ​of​ ​desired​ ​reactant​ ​or​ ​product

Mass​ ​=​ ​moles​ ​x​ ​molar​ ​mass(of​ ​the​ ​product)​ ​to​ ​find​ ​mass

how to find the formulae of compounds

weigh​ ​some​ ​pure​ ​magnesium

Heat​ ​magnesium​ ​to​ ​burning​ ​in​ ​a​ ​crucible​ ​to​ ​form​ ​magnesium​ ​oxide,​ ​as​ ​the magnesium​ ​will​ ​react​ ​with​ ​the​ ​oxygen​ ​in​ ​the​ ​air

weigh​ ​the​ ​mass​ ​of​ ​the​ ​magnesium​ ​oxide

Known​ ​quantities:​ ​mass​ ​of​ ​magnesium​ ​used​ ​&​ ​mass​ ​of​ ​magnesium​ ​oxide produced​ ​

Required​ ​calculations:​ ​

mass oxygen = mass magnesium oxide - mass magnesium

moles magnesium = mass magnesium / molar mass magnesium

moles oxygen = mass oxygen / molar mass oxygen

definitions

the weight of a body acts through its centre of gravity

empirical formula- the simplest whole number ratio of atoms of each element in a compound

calculate empirical and molecular formulae

empirical from the formula of molecule

if you have a common multiple e.g. Fe2O4 the empirical formula is the simplest whole number ratio, which would be FeO2

if there is no common multiple, you already have the empirical formula

molecular from empirical formulae

Find relative molecular mass of the empirical formula

Divide relative molecular mass of compound by that of the empiricalformula

Multiply the number of each type of atom in the empirical formula by this number

molar volumes of gas

Volume (dm3) of gas at RTP = Mol. x 24

amount of substance, volume and concentration

mass = conc x vol

g/dm3 x dm3

equations

(g)​ ​means​ ​gas,​ ​(s)​ ​means​ ​solid,​ ​(l)​ ​means​ ​liquid,​ ​(aq)​ ​means​ ​aqueous

Example​ ​of​ ​word​ ​equation:​ ​hydrochloric​ ​acid​ ​+​ ​sodium​ ​hydroxide​ ​->​ ​sodium chloride​ ​+​ ​water

Example​ ​of​ ​balanced​ ​chemical​ ​equation:​ ​HCl​ ​+​ ​NaOH​ ​->​ ​NaCl​ ​+​ ​H​2O​

to​ ​balance​ ​an​ ​equation:​ ​you​ ​need​ ​to​ ​make​ ​sure​ ​there​ ​are​ ​the​ ​same​ ​number​ ​of

each​ ​element​ ​on​ ​each​ ​side​ ​of​ ​the​ ​equation​ ​and​ ​if​ ​there​ ​isn’t​ ​use​ ​big​ ​numbers​ ​at the​ ​front​ ​of​ ​a​ ​compound​ ​to​ ​balance​ ​it​ ​e.g.​ ​3H2​ O​

relative formula mass

Relative​ ​formula​ ​mass​ ​(Mr)​ ​of​ ​a​ ​compound:​ ​sum​ ​of​ ​the​ ​relative​ ​atomic​ ​masses​ ​of the​ ​atoms​ ​in​ ​the​ ​numbers​ ​shown​ ​in​ ​the​ ​formula

the mole

Chemical​ ​amounts​ ​are​ ​measured​ ​in​ ​moles​ ​(therefore​ ​it​ ​is​ ​the​ ​amount​ ​of substance).​ ​The​ ​symbol​ ​for​ ​the​ ​unit​ ​mole​ ​is​ ​mol.

The​ ​mass​ ​of​ ​one​ ​mole​ ​of​ ​a​ ​substance​ ​in​ ​grams​ ​is​ ​numerically​ ​equal​ ​to​ ​its​ ​relative formula​ ​mass.

1.26​ ​calculate​ ​relative​ ​formula​ ​masses​ ​(including​ ​relative​ ​molecular​ ​masses)

(Mr)​ ​from​ ​relative​ ​atomic​ ​masses​ ​(Ar)
For​ ​example,​ ​the​ ​Ar​ ​of​ ​Iron​ ​is​ ​56,​ ​so​ ​one​ ​mole​ ​of​ ​iron​ ​weighs​ ​56g.

The​ ​Mr​ ​of​ ​nitrogen​ ​gas​ ​(N​2)​ ​is​ ​28​ ​(2x14),​ ​so​ ​one​ ​mole​ ​is​ ​28g.

One​ ​mole​ ​of​ ​a​ ​substance​ ​contains​ ​the​ ​same​ ​number​ ​of​ ​the​ ​stated​ ​particles, atoms,​ ​molecules​ ​or​ ​ions​ ​as​ ​one​ ​mole​ ​of​ ​any​ ​other​ ​substance

moles​ ​=​ ​mass​ ​÷​ ​relative​ ​atomic​ ​mass

structure

Metals consist of giant structures of atoms arranged in a regular pattern

The electrons in the outer shell of metal atoms are delocalised and so are free to move through the whole structure

The sharing of delocalised electrons gives rise to strong metallic bonds.

definition

Strong electrostatic attraction between negatively charged electrons and positive metal ions

properties of metals

high melting and boiling points

conduct heat and electricity because of the delocalised
electrons in their structures.

layers of atoms in metals are able to slide over each other, so metals, can be bent and shaped.

covalent compounds do not conduct electricity as they do not have free electrons

ionic compounds conduct electricity when molten or aqueous because

Ions are fixed when ionic compounds are solid, meaning they can’t move so can’t conduct electricity

when the compounds are molten or in aqueous solution, the ions (that are electrically charged) are able to move and carry charge

anion and cation

anion is a negatively charged ion

cation is a positively charged ion

experiments

During electrolysis, positively charged ions move to the negative electrode (cathode), and negatively charged ions move to the positive electrode (anode) where they gain/ lose electrons and are reduced or oxidised

aqueous solutions

molten compounds

mocvement of ions

when the ions reach the electrodes they either gain or lose electrons and are discharged (they lose their charge)

elements are formed at the electrodes when the charges are lost

half equations

half equations represent what is happening at each electrode

the ion is written on the left of the equation arrow

finally balance the equation in terms of charge by adding the electrons (e-)

electrodes are typically made of an inert substance such as graphite or platinum so the electrodes do not react with the electrolyte or the products made in electrolysis

lower temperature means that it is more cost effective but using aqueous solutions can make it more difficult to predict the products as there are ions present in water as well

e.g NaCl

the sodium and chloride ions split up, giving Na+ and Cl- ions

water molecules also split up giving H+ and OH- ions

formation of hydrogen and oxygen

at the cathode hydrogen is produced if the metal is more reactive than hydrogen (2H2O + 2e- -> H2 + 2OH-

at the anode if group 7 ions are present then a halogen will be made, if carbonate, sulfate or nitrate ions are present, oxygen will form (2H20 -> 4H+ + O2 + 4e-

states of matter

three states of matter

solids

strong forces of attraction between particles, so particles are held in a fixed position, forming a regular lattice arrangement

the particles don't move, they vibrate around a fixed position

they have a defined shape and volume

they have low kinetic energy

liquids

they have medium kinetic energy

weak force of attraction, so are randomly arranged and are free to move around each other, while still touching

they have a definate volume but not a definate shape, so will fill the bottom of a container

the particles are constantly moving with random movement, with the speed increasing as heat increase.

gas

very weak forces of attraction so are free to move and are far apart. they move in straight lines

they don't keep a definite shape or volume and will always fill any container

they are constantly moving with random motion, with the hotter the gas gets, the faster they move

they have high kinetic energy

interconversions

solid #

melting

liquid

evaporating/boiling

gas

condensing #

desublimation

freezing

[sublimation]

when a solid is heated, its particles gain more energy. this makes the particles vibrate more, which weakens the forces that hold the solid together. at certain temperatures, the particles have enough energy to break free from their positions. this is melting

when a liquid is heated, the particles get even more energy. this energy makes the particles move faster, weakening the bonds and breaking them. at certain temperatures, the particles have enough energy to break their bonds. (evaporation)

dilution

when water is added to a solution, the colour becomes less intense and the solution becomes more dilute

diffusion

the net movement of particles from a high concentration to a low concentration

potassium manganate and water

add potassium manganate to a beaker of water. the purple colour slowly spreads out to fill the beaker. the particles of potassium manganate are diffusing among the particles of water., eventually becoming spread out through the water

ammonia and hydrochloric acid

if you set up a tube, with cotton wool soaked in aqueous ammonia in one end and cotton wool soaked in HCl the other end, the NH3 gas diffuses from one end of the tube and the HCL gas diffuses from the other. When they meet, they react to form ammonium chloride. the ring doesn't form exactly in the middle, it forms nearer the end of the HCl as it is heavier so diffuse slower

bromine and air

fill half a gas jar with bromine gas, and the other half full of air. separate the 2 with a glass plate. when you remove the glass plate, the brown bromine gas diffuses through the air, and eventually it will diffuse right through the air

solubility

the measure of how much solute will dissolve in a solvent

measured in g per 100g of solvent

as pressure of gases increases, solubility increases

as temperature of gases increases, solubility decreases

solubility curves

To plot a solubility curve, the maximum mass of solvent that can be dissolved in 100 g of water before a saturated solution is formed, is determined at a series of different temperatures

practical

Prepare a two beakers, one as a hot water bath and one as an ice bath

Using a small measuring cylinder, measure out 4 cm3 of distilled water into a boiling tube.

On a balance weigh out 2.6 g of ammonium chloride and add it to the boiling tube

Place the boiling tube into the hot water bath and stir until the solid dissolves

Transfer the boiling tube to the ice bath and allow it to cool while stirring

Note the temperature at which crystals first appear and record it in a table of results

Add 1 cm3 of distilled water then warm the solution again to dissolve the crystals

Repeat the cooling process again noting the temperature at which crystals first appear.

Continue the steps until a total of 10 cm3 of water has been added

definitions

solute

the substance being dissolved

solvent

the liquid it disolves into

solution

a mixture of solute and solvent that doesn't separate

saturated solution

a solution where the maximum amount of solute has been dissolved, so no more will dissolve in the solution

elements, compounds and mixtures

separation techniques

simple distillation

Used​ ​to​ ​separate​ ​a​ ​pure​ ​liquid​ ​from​ ​a​ ​mixture​ ​of​ ​liquids

fractional​ ​distillation

The​ ​oil​ ​is​ ​heated​ ​in​ ​the​ ​fractionating​ ​column​ ​and​ ​the​ ​oil​ ​evaporates​ ​and condenses​ ​at​ ​a​ ​number​ ​of​ ​different​ ​temperatures.

The​ ​many​ ​hydrocarbons​ ​in​ ​crude​ ​oil​ ​can​ ​be​ ​separated​ ​into​ ​fractions​ ​each of​ ​which​ ​contains​ ​molecules​ ​with​ ​a​ ​similar​ ​number​ ​of​ ​carbon​ ​atoms

The​ ​fractionating​ ​column​ ​works​ ​continuously,​ ​heated​ ​crude​ ​oil​ ​is​ ​piped​ ​in at​ ​the​ ​bottom.​ ​The​ ​vaporised​ ​oil​ ​rises​ ​up​ ​the​ ​column​ ​and​ ​the​ ​various fractions​ ​are​ ​constantly​ ​tapped​ ​off​ ​at​ ​the​ ​different​ ​levels​ ​where​ ​they condense.

The​ ​fractions​ ​can​ ​be​ ​processed​ ​to​ ​produce​ ​fuels​ ​and​ ​feedstock​ ​for​ ​the petrochemical​ ​industry.

filtration

if​ ​you​ ​have​ ​produced​ ​e.g.​ ​a​ ​precipitate​ ​(which​ ​is​ ​an​ ​insoluble​ ​salt),​ ​you
would​ ​want​ ​to​ ​separate​ ​the​ ​salt/precipitate​ ​from​ ​the​ ​salt​ ​solution.

crystallisation

If​ ​you​ ​were​ ​to​ ​have​ ​produced​ ​a​ ​soluble​ ​salt​ ​and​ ​you​ ​wanted​ ​to​ ​separate this​ ​salt​ ​from​ ​the​ ​solution​ ​that​ ​it​ ​was​ ​dissolved​ ​in

paper​ ​chromatography

Used​ ​to​ ​separate​ ​mixtures​ ​and​ ​give​ ​information​ ​to​ ​help​ ​identify substances

Involves​ ​a​ ​stationary​ ​phase​ ​and​ ​a​ ​mobile​ ​phase

Separation​ ​depends​ ​on​ ​the​ ​distribution​ ​of​ ​substances​ ​between the phases

pure vs impure

a pure substance is a single element or compound, not mixed with any other substance

pure substances melt and boil at specific temperatures so melting and boiling data can be used to distinguish pure substances from mixtures which melt over a range of temperatures

definitions

element

substances made from only one type of atom

compounds

substance made from two or more elements that have reacted chemically with each other

mixture

consists of two or more elements or compounds not chemically combined together

chemical properties of each substance in the mixture are unchanged

chromatogram

Compounds​ ​in​ ​a​ ​mixture​ ​may​ ​separate​ ​into​ ​different​ ​spots​ ​depending​ ​on​ ​the solvent​ ​but​ ​a​ ​pure​ ​compound​ ​will​ ​produce​ ​a​ ​single​ ​spot​ ​in​ ​all​ ​solvents

chromatography practical

Use a ruler to draw a horizontal pencil line 2 cm from the end of the chromatography paper

Use a different capillary tube to put a tiny spot of each colouring A, B, C and D on the line

Use the fifth tube to put a small spot of the unknown mixture U on the line

Make sure each spot is no more than 2-3 mm in diameter and label each spot in pencil

Pour water into the beaker to a depth of no more than 1 cm and clip the top of the chromatography paper to the wooden spill. The top end is the furthest from the spots

Carefully rest the wooden spill on the top edge of the beaker. The bottom edge of the paper should dip into the solvent

Allow the solvent to travel undisturbed at least three quarters of the way up the paper

Remove the paper and draw another pencil line on the dry part of the paper as close to the wet edge as possible. This is called the solvent front line

Measure the distance in mm between the two pencil lines. This is the distance travelled by the water solvent

For each of food colour A, B, C and D measure the distance in mm from the start line to the middle of the spot

Rf values

Rf​ ​value​ ​=​ ​distance​ ​moved​ ​by​ ​substance​ ​/​ ​distance​ ​moved​ ​by​ ​solvent​ ​(​ ​/ represents​ ​a​ ​dividing​ ​sign)

atomic structure

atoms and molecules

All​ ​substances​ ​are​ ​made​ ​of​ ​atoms

A​ ​substance​ ​with​ ​only​ ​one​ ​sort​ ​of​ ​atom​ ​=​ ​element

An​ ​atom​ ​is​ ​the​ ​smallest​ ​piece​ ​of​ ​an​ ​element​ ​that​ ​can​ ​exist

A​ ​molecule​ ​=​ ​formed​ ​when​ ​atoms​ ​join​ ​together​ ​by​ ​chemical​ ​bonds​ ​(can​ ​be​ ​made

of​ ​atoms​ ​of​ ​the​ ​same​ ​element)

structure

proton

charge - +1

mass - 1

neutron

charge - 0

mass - 1

electron

charge - -1

mass - 1/2000

relative atomic mass

[(mass of isotope A x % isotope A) + (mass of isotope B x % isotope B)] / 100

definitions

Atomic​ ​(proton)​ ​Number​ ​=​ ​number​ ​of​ ​protons​ ​(=​ ​number​ ​of​ ​electrons​ ​if​ ​it’s​ ​an atom,​ ​because​ ​atoms​ ​are​ ​neutral)

Mass​ ​(nucleon)​ ​Number​ ​=​ ​number​ ​of​ ​protons​ ​+​ ​neutrons

Isotopes​ ​=​ ​different​ ​atoms​ ​of​ ​the​ ​same​ ​element​ ​containing​ ​the​ ​same​ ​number​ ​of protons​ ​but​ ​different​ ​numbers​ ​of​ ​neutrons​ ​in​ ​their​ ​nuclei

Relative​ ​atomic​ ​mass​ ​(of​ ​an​ ​element)​ ​=​ ​an​ ​average​ ​value​ ​that​ ​takes​ ​account​ ​of the​ ​abundance​ ​of​ ​the​ ​isotopes​ ​of​ ​the​ ​element

covalent bonding

giant covalent structures properties

Substances that consist of giant covalent structures are solids with very high melting points.

All of the atoms in these structures are linked to other atoms by strong covalent bonds.

These bonds must be overcome to melt or boil these substances.

why do the melting and boiling points of substances with simple molecular structures increase with increasing relative molecular mass

the intermolecular forces increase with the size of the molecules, so larger molecules have higher melting and boiling points

simple molecular structures

Substances that consist of small molecules are usually gases or liquids that have
low boiling and melting points.

substances that consist of small molecules with weak intermolecular forces between the molecules. these are broken in boiling or melting, not the covalent bonds

Substances that consist of small molecules don't conduct electricity, because small molecules do not have an overall electric charge

Strong bonds between atoms that are covalently bonded are the result of electrostatic attraction between the positive nuclei of the atoms and the pairs of negative electrons that are shared between them

covalent bonds

Covalent bonding occurs in most non-metallic elements and in compounds of nonmetals

When atoms share pairs of electrons, they form covalent bonds. These bonds between atoms are strong.

covalent molecules do not conduct electricity with the exception of graphite and graphene

carbon allotropes

diamond

hard

high melting point

each carbon bond is joined to 4 other carbon bonds

graphite

each carbon atom is covalently bonded to 3 other carbons, forming layers of hexagonal rings, which have no covalent bonds between layers

the layers can slide over each other due to having weak intermolecular forces between them, rather than covalent bonds

soft

slippery

one electron is delocalised so can conduct electricity

graphene

single layer of graphite

has properties that make it useful in electronics and composites

fullerenes

molecules of carbon atoms with hollow shapes

based on hexagonal rings of carbon atoms, but may also contain rings of five or seven carbon atoms

carbon nanotubes

cylindrical fullerenes with very high length to diameter ratios

their properties make them useful for nanotechnology, electronics and materials