Chemistry module 2

the atom + foundations

protons electrons and neutrons info

protons

mass: 1 charge: +1 location: in nucleus

electrons

mas: 1/1836 charge: -1 location: outside nucleus

neutrons

mass: 1 charge: 0 location: in nucleus

atomic number definition

The atomic number is the number of protons in the nucleus of an atom of an element

isotope definition

atoms of the same element that have the same number of protons but different numbers of neutrons

mass number definition

total number of protons and neutrons

ions definition

an atom that has gained or lost electron(s)

Relative molecular mass definition

the average mass of a molecule compared to 1/12 the mass of one atom of carbon

Relative atomic mass definition

the average mass of one atom compared to 1/12 the mass of one atom of carbon

formular for finding RAM using isotopes

(% x isotope mass) + (% x isotope mass) + … ) / 100

simple ions for: H, Al , O₂ , N , Ag , Zn

H⁺, Al³⁺, O^2-, N^3-, Ag⁺, Zn²⁺

complex ions for: NH₄ (ammonium) , CO₃ (carbonate) , OH (hydroxide) , SO₄ (sulphate), NO₃ (nitrate)

NH4+, CO3 2-, OH-, SO4 2-, NO3-

conversions of units:

C to K , Cm³ to dm³ , cm³ to m³ , dm³ to m³

c-k +273, cm3 to dm3 ÷ 1000, cm3 to m3 ÷ 1,000,000, dm3 to m3 ÷ 1,000

concentration equation

c= n/v or c=m(g)/v(dm)

Moles and Avogadro definition

A mole is the amount of a substance that contains the same number of particles as the number of Carbon-12 atoms in 12g

Avogadro’s number definition and formulars

the number of particles in a mole 6.02 × 10²³

moles = mass / Mr and amt of particles = amt of moles x 6.02×10²³

all formulars that deal with moles (4)

gas law: PV=nRT

concentration: c = n/V

mass= n x Molar Mass

Avogadro: number of particles= n x 6.02 × 10²³

empirical vs molecular formular

Empirical formula shows the simplest integer ratio of elements in a compound, while the molecular formula displays the actual number of atoms of each element in a molecule.

equations with salts

formular is xsalt . xh20

find the moles of each then use the ratio to find x

or use the mass to see how many moles of water are present

remember this is a reversible reaction

ideal gas equation and variations (4)

PV=nRT n=PV/RT V=nRT/P T=PV/nr

pressure (Pa) x volume(m³ ) = number of moles x ideal gas constant x temperature (K)

percentage yield equation and reasons for it being lower then total mass

actual yield / theoretical yield x100

reactions don’t always go to completion some reactants don’t react and are left over loss of product difficulty separating/spilling side reactions forming

Atom economy and jhow it can be improved

Mr of useful products/ Mr of all products x100

-alternative reaction pathways -finding uses for waste products

common formulars to know acids (5)

HCl , H₂SO_{4 ,}H3PO4, CH3COOH , HNO₃

Common formulars to know alkaline (3)

NaOH, KOH , NH₃

strong and weak acids differences

Strong acids fully dissociate H⁺ in water, while weak acids only partially dissociate. Strong acids have a higher conductivity and lower pH compared to weak acids.

neutralisation equation

H+ + OH- → H2O (reversible)

salt equations (4)

Metal + acid = salt + hydrogen

Metal oxide + acid = salt + water

Metal hydroxide + acid = salt + water

metal carbonate salt + carbon dioxide + water

redox reactions (3)

OIL RIG

(Oxidation Is Loss, Reduction Is Gain) of electrons.

lower= reduced higher= oxidised

disproportionation reactions are when the same element gerts O and R

shells, subshells and orbitals and order

shell eg 2s and 2p

subshell eg 3p

orbital is one cell

1s2,2s2,2p6,3s2,3p6,4s2,3d10,4p6

properties of ionic structures

giant ionic lattices have high boiling a melting point due to STRONG electrostatic attractions that require large amounts of energy to overcome. They also conduct electricity when molten or dissolved in water.

soluble as polar molecules can interact with ions ,hard and brittle

covalent bonding structures

sharing of electrons

low melting and boiling points due to weak intermolecular bonds not soluble BUT has strong intramolecular bonds

dative covalent bond is when 1 element gives both electrons for the bond

shapes of molecules, bond angles and bonding pairs

linear 180 bp=2 lp=0

trigonal planar 120 bp=3 lp=0

tetrahedral 109.5 bp=4 lp=0

trigonal pyramidal 107 bp=3 lp=1

non linear 104.5 bp=2 lp=2

octahedral 90 bp=6 lp=0

VSPER theory

level of repulsion of electrons on the outer shell

lone pair x 2 > lone pair bonding pair > boding pair x2

electronegativity

is how much am element will attract electrons

down a group: electronegativity decreases increase in shells and shielding makes nuclear attraction between the nucleus and outer electrons weaker

across a period: electronegativity increases number of protons increase and radius decreases increasing the nuclear attraction between nucleus and outer e-

Bond polarity

permanent- permeant dipoles forces made from atoms with different electronegativity - strong attractions between molecules

London forces: weak intermolecular forces due to temporary dipoles. not found in ionic strength depends on amt of electrons shape of molecules contact area

hydrogen bonding: when H is bonded to O N F very strong- high bp and mp

is it polar?

needs to be:

a difference in electronegativity and asymmetrical