F321 Definitions
Revision for the basics in F321
- Created by: Rebecca McNickle
- Created on: 14-11-12 16:51
F321
First Ionisation energy- The energy required to remove 1 electron from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions
Factors effecting Nuclear Attraction:
1) Nuclear Charge
2) Electron sheilding
3) Nuclear Radius
Shell Sub-shell Total Electrons
1 1s 2
2 2s, 2p 8
3 3s, 3p,3d 18
4 4s, 4p, 4d, 4f 32
F321
S orbital are spherical
P orbitals are a 3D dumbell shape
Sub Shell No. orbitals Maximum number of Electrons
S 1 2
P 3 6
D 5 10
F 7 14
F321
Ions: mg -> mg(2+) + e(2-)
Giant Ionic Lattice:
+ and - ions, brittle ,held together by electrostatic attraction, high melting and boinling point, doesn't conduct electricity when solid, conducts when molten as ions can move, soluble
Some elements can form multiple ions e.g. Fe(II) 2+ ions, Fe(III) 3+
1+ : Ammonuim NH4
1- : Hydroxide OH , Nitrate NO3 , Nitrite NO2 , Hydrogen carbonate HCO3
2- : Carbonate CO3 , Sulphate SO4 , Sulphite SO3 , Dichromate Cr2O7
3- : Phosphate PO4
F321
SO4 (2-) Al (3+) = Al2(SO4(3
Covalent bond- bond formed over a shared pair of electrons
Lone pair of electrons- any pair of electrons not invloved in bonding
Dative Covalent Bond- One atom supplies a lone pair of electrons to the covalent bond which are shared by an atom with a vacant orbital
Octet Rule:
Group 5- P, As
Group 6- S, Se, Te
Group 7- Cl, Br, I, At,
F321
Molecule No. of electron pairs Bond Angle Name of Shape
BF3 3 120 Triagonal Planar
CH4 4 109.5 Tetrahedral
SF6 6 90 Octtahedral
Lone pairs are more repulsive so as it is a more dense area of electrons therefore there it decreases the bond angle by 2.5 degrees for each pair
Molecule Lone pairs Bond angle Name of shape
NH3 1 107 Pyramidal
H20 2 104.5 Non Linear
F321
Molecules with multiple bonds
Molecules with double bonds each double bond is treated as a bonded region
CO2 2 bonded regions 180 Linear
Electronegativity- is a measure of teh attraction of a bonded atom for a pair of electrons in a covalent bond
effecting factors : Atomic Charge Atomic Radius Electron Sheilding
When 2 atoms in a compound are identical the electrons are shared equally= non polar
If there is a difference in charge it is called a permemant dipole
Symmetrical molecules are non polar as the dipoles cancell each other out
Polar- difference in charge
F321
Key Concept!
- The greater the distance in electronegativity between the binded atoms the greater the dipole
- The more electronegative atom will take the the slighty negative charge
Down a group -More shells, more sheilding so electronegativity decreases
Across a period -Nuclear charge increases so electronegativity increases
Covalent -> Ionic
No difference between electronegativity = non polar covalent bond
Small difference between electronegativity = polar covalent
Large different between electronegativity = ionic as the electron is just taken
F321
Intermolecular forces are weak!
Intramoleculcar forces are strong!
Bong type Relative Strength
Ionic / Covalent 1000
Hydrogen 50
Dipole- Dipole 10
Van der Waals' 1 (caused by electron movement)
F321
Van der waals forces are between all molecules/ atoms, whether they are polar or non polar. They cause all atoms to be attracted to each other
- They are the weakest time of intermolecular force
- Act between small temporarary dipoles in neigbouring molecules
ELECTRONS ARE ALWAY MOVING this means the electrons are likely to move more to one side than the other this creates a temporary dipole (instantaneous) These are destroyed and created constantly,
If a neighbouring molecule has a tempory dipole the +/- charge will cause electrons to attract or repell creating induced tempory dipoles. This can also set up a domino effect.
F321
Effecting Factors:
Greator numbers of electrons = larger induced dipole = greater Van der Waals' forcesThe greater the points of contact = larger Van der Waals' forces
Boiling points increase due to more electrons which creates larger Van der Walals' forces also the larger forces make bonds harder to break needing more energy to break them.
F321
Hydrogen Bonding : A strong Dipole- Dipole Bond
Attraction between :
- An electron deficient hydrogen atom on one atom
- A lone pair of electrons on a highly electronegative atom
F321
Properties on Hydrogen Bonding:
- Why do icebergs float?- Ice is less dense than water. When water freezes the stronf hydrogen bonds hold together the water in a lattice shape .This lattice contains spaces between the molecules therefore less dense
- How do pond skaters walk on water?- The extra intermolecular bonding of hydrogen bonds creates surface tension and viscosity. The surface tension allows pond skater to walk on water as they are practically walking on hydrogen bonds
- The glue in DNA- They are responsible for creating the double helix shape.
F321
Metallic Bonding
The Giant lattice is held together by the attraction between + ions and - delocalised electrons
High Melting/Boiling Points
Strong +/- attraction high tempertures are needed to displace protons and break bonds
F321
Good Cunductivity
Delcocalised elctrons carry the charge along the metal
Mallebility and ductility
Ductile: Stretchable Malleable: can be hammered into shape
Layers can move over each other and slide past each other
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