Thermochemistry

Entropy

the amount of disorder of energy nad matter in a system

S total

S system + S surroundings

Electronegativity

Ability of an atom in a bond to attract electrons towards itself

Ionisation energy

The energy to remove one mol of electrons from one mol of gaseous atoms 

Across period

increase protons/nuclear attractive charge

Down group

Increase shells/sheilding 

temporary dipole-dipole

all molecules, weakest, vary based on electron cloud

permanant dipole-dipole

polar molecules

IM attractions depend on

• e- clouds 

• molecules shape

• polarity 

• hydrogen bonding

Hydrogen bonding

FON, strongest

Measuring enthalpy change reasons for loss of temp 

• insulating lid and cup

• incomplete reactions

Fus

s to l

vap

l to g

comb

1 mol of substance burned in oxygen

Bonds broken

endo as energy absorbed to break IM

Bonds formed 

exo as energy released as IM formed 

6 regions

octahedral - octahedral, square pyramid, square planar 90

5 regions

trigonal bipyramidal - trigonal bipyramidal, seesaw, T-shaped 90, 120

4 regions

Tetrahedral - tetrahedral, trigonal pyramid, v/bent 109.5

3 regions

Trigonal planar - trigonal planer, v/bent 120

2 regions

linear 180

electron configuration

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

Shape/polarity

around the central atom there are regions of electron density. These regions repel to maximise seperation and minimise repulsion giving an electron geometry of. Since there are bonding pairs and non-bonding pairs it gives an overal shape of. in x-y pairs x is more electronegative then y. this creates a dipole. These dipoles are arranged meaning these dipoles meaning it is a polar molecule

Ionisation energy increase

up period, right group

Radius increase

down period, left group

Entropy answer

• What has changed (no. mols/phase)

• System endo/exo

• Surrounding endo/exo

• conclude entropy increase/decrease

Electron configuration

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

ionisation energy eq

X(g) → X^+(g) + e^-