chemistry topic 1

Development of atomic model

Development of atomic model

Dalton-tiny hard spheres-All substances are made of atoms. Atoms are small particles that cannot be created, divided, or destroyed.

Thomson-plum pudding model-negative electrons are scattered throughout soft blobs of positively charged material.

Rutherford-alpha particles shot at gold foil,discovered dense region in the middle (nuclues),electrons travel around nucleus

Calculate the relative atomic mass

= ​(mass of isotope-A x % of isotope-A) + (mass of isotope-B x % of isotope-B) ​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​/ 100

Mendeelevs arrangments

in order of atomic mass,but left gaps for non discovered elements. realised elements with similar properties belonged in the same groups

metals vs non metals

metals-react to form + ions,loose elements in order to form these ions,forming stable structure like noble gas

non-metals- form - ions,gain electrons to be stable like noble gas

ionic bonds

transfer of electrons to produce a full outer shell between METAL and NON METAL

form cations and anions

FORCE OF ATTRACTION BETWEEN OPP CHARGED IONS =ELECTROSTATIC FORCE

ionic compounds

High melting and boiling points

Conduct electricity-but only as water/liquid=ions are free to move (delocalised)

-ide/-ate

-ide= non metal forms a negative ion

-ate=when a compound contains oxygen asw another element,NON METAL FORMS THIS ONLY

lattice structure

a giant structure of ions

held by strong electrostatic forces,which act in all directions

regular arrangement of ions

covalent bonds

sharing of electrons,with NON METALS

INTERMOLECULAR FORCES

leads to formation of molecules=SIMPLE/GIANT COVALENTS

Simple molecular substances COVALENT RMBR!

low boiling and melting points=weak intermolecular forces

dont conduct electricity=no overall charge -but when broken down in water they do

Many are insoluble in water, but some are soluble=can form intermolecular forces with water stronger than water molecules

Giant covalent structures

strong intermolecular forces

high melting and boiling points

some conduct electricity

insoluable in water

metallic bonding

giant structure of atoms arranged in regular patterns

delocalised electrons = contains heat and electricity=gives strong metallic bonds

high melting and boiling points

STRENGTH

malleable=atom layers can slide over eachother

Electrostatic forces

coductivity=ability for electrons to moce

INsoluable

Diamond

carbon joined to 4 other carbon atoms

no free electrons=cannot conduct

rigid strucute w strong covalent bonds =cutting tools/diamond tipped drils

high melting points

graphite

bonded to 3 other carbons=forms layers w hexagonal rings

layers can slide=weak intermolecular forces=soft & slippery

one delocalised electron = conducts electricity

pencils/lubricants/electrodes

Graphene

-single layer of graphite

high melting points

strong =regular arrangement

useful in electronics and composites

Fullerenes

molecular form of carbon with hollow shapes eg nano tubes and buckyballs

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

first fullerene to be discovered was Buckminsterfullerene (C60), which has a spherical shape

Carbon nanotubes

cylindrical fullerenes,high length to diameter ratios

used in nanotech,electronics and tennis racket frames

high tensile strength(tension)

conduct electricity

Buckyballs

spheres of carbon atoms

weak intermolecular forces

little energy=low boiling points and slippery

polymers

large molecules with repeat units

strong covalent bonds

solids at room temp

allotropes

two subsatnces made from same elemetns,same physical state but different structures rg diamond and grpahite

law of conservation mass

total mass before a reactions=totals mass after

concetraition of a solution

mass/volume

cm³ to dm³?

/1000

What is the definition of one mole of particles of a substance?

The Avogadro constant number of particles of that substance

or

a mass of ‘relative particle mass’

How do you calculate the number of moles of a substance? (2 equations)

Number of moles = mass (g) / relative formula mass

Number of moles = number of particles / Avogadro’s constant