Chp 2 - Electrons, Bonding, Structure Flashcards
Number of electrons in first 4 energy levels (shells)?
1st Shell 2
2nd Shell 8
3rd Shell 18
4th Shell 32
Names the electron sub-shells?
+max electrons in those shells
S-orbital (Max= 2 electrons)
P-orbital. (Max= 6 electrons)
D- orbital (Max = 10 electrons)
Shape of s-orbital?
Circle around nucleus
(See notes)
Shape of p-orbital?
Figure of 8
(Dumbbell around nucleus across three planes)
See notes
Def of orbital?
an orbital is an area of space about the nucleus that can hold a maximum of two electrons with opposite spins (high likelihood of finding an electron)
sub-shell notation of oxygen?
1s^2 2s^2 2p^4
Filling orbital?
Fill orbitals singularly before pairing up
Energy levels?
How do electrons begin to fill the p orbitals?
They fill singularly before pairing up in the orbitals
Order of filling
Ions
an atom with more or less electrons than protons and therefore has a charge – either positive or negative
Def of ionic bonding
Electrostatic attraction between positive and negative ions.
Structure of ionic compounds
(+ why)
Giant ionic crystal lattice structure
(Resulting from oppositely charged ions strongly attracted in all directions)
Physical Properties of ionic compounds ?
High melting point
- large amounts of energy needed to overcome strong electrostatic attraction
Brittle
- dislocation leads to layers moving and similar ions being adjacent causing repulsion to split crystal
Water soluble
- polar solvent stabilises and separates ions
Electrical conductivity
- in L/AQ form ions are mobile and able to conduct
As solid = insulator
Def of covalent Bond?
The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms
{def of average bond empathy}
A measure of the strength of a covalent bond
(the stronger the bond the higher the value)
Structures of covalent compounds?
Simple molecular
Giant covalent
(Polymers)
Describe dative covalent (Co-ordinate) bonds
A covalent bond formed where both electrons come from the same species
Drawn with -> rather than – in display formula
Draw diagram to show formation of co-ordinate bond
BF3 + F- —> BF4-
Lone pair of electrons donated from F- to B in BF3
(See notes for diagram)
Types of chemical bonds
(Strong bonds)
- Ionic
- Covalent
- Dative ( coordinate)
- Metallic
Types of physical bonds
(Weak bonds)
- Induced dipole-dipole interactions (London forces)
- permanent dipole-dipole interactions
- hydrogen bonds
Shape and bond angles of 2 bonds
(Species without lone pairs)
Shape- linear
Bond angle- 180 o
Eg. BeCl2
Shape and bond angles of 3 bonds
(Species without lone pairs)
Shape- trigonal planar
Bond angles- 120 o
Eg. BF3
Shape and bond angles of 4 bonds
(Species without lone pairs)
Shape- tetrahedral
Bond angles- 109.5 o
Eg. CH4
Shape and bond angles of 5 bonds
(Species without lone pairs)
Shape- trigonal bipyramidal
Bond angles- 120 & 90 o
Eg. PF5
Shape and bond angles of 6 bonds
(Species without lone pairs)
Shape- octahedral
Bond angles- 90 o
Eg. SF6
Effect of lone pairs on bond angle?
[+why]
Each lone pair reduces the bond angle by 2.5 o
This is because they have a greater repulsion power
Describe shape of water molecule?
Shape= non-linear
Bond angles= 104.5
As has 2 bonded pairs and 2 lone pairs of electrons
Why might shapes be non-linear ?
Electron pair repulsion tells us the lone pairs have a higher repulsion force therefore decrease the bond angle by 2.5o
Def of electronegativity?
Electronegativity is the ability of an atom to attract the bonding electrons in a covalent bond
Electronegativity changes across the periodic table?
(Pauling value)
Electronegativity increases up the groups and across the periods towards fluorine
When is polar bonds formed (permanent dipole)?
When molecules containing covalently-bonded atoms with different electronegativities.
When is a polar molecule (overall permanent dipole) formed?
A polar molecule requires polar bonds with dipoles that do not cancel due to their direction.
(Not symmetrical)
When do hydrogen bonds form?
As intermolecular bonding between molecules containing N,O,F and the H atom of -NH, -OH, -HF
Why are water molecules properties unusual?
Ice is less dense than water-
relatively high melting and boiling point-
describe how London forces arise
(3 marks)
1) uneven distribution of electrons
2) creates instantaneous dipole
3) induces dipoles of neighbouring molecules
