2.2 Electrons, Bonding and Structure (completed) Flashcards
2.2.1 Electron structure 2.2.2 Bonding and structure
Shells are regarded as what?
Energy levels
What happens to energy as the shell number increases?
Energy increases
What are shells made up of?
Orbitals
How many electrons can be held in an orbital?
One or two, no more.
What are the different orbitals?
S-orbitals
P-orbitals
D-orbitals
F-orbitals
How many electrons does each sub shell contain?
S - two P - six D - ten F - fourteen (+four)
What is the shape of an s-orbital?
Spherical
What is the shape of a p-orbital?
Dumbell
What are the rules of orbital fillings?
Orbitals fill in order of increasing energy.
Orbitals with the same energy are occupied singly first then pair up with opposite spins.
Where does this rule cause confusion for 3d and 4s?
The 3d sub-shell has higher energy than the 4s.
So the 4s fills before the 3d. Then when the 4s fills up it takes higher energy level than the 3d, so the 4s loses electrons first.
How do electrons pair up in orbitals?
They have opposite spins and so this counteracts the repulsion
How can electron configuration be shortened?
1s2 can be expressed as [He]
1s2 2s2 2p6 can be expressed as [Ne]
1s2 2s2 2p6 3s2 3p6 can be expressed as [Ar]
What is the definition of first ionisation energy?
The amount of energy needed to remove one mole of electrons
from each atom in one mole
of an element in the gaseous state
Why do successive ionisation energies increase?
Each one is closer to the nucleus each time so requires more energy as there is a greater inbalance of positive and negative charges which requires more energy to overcome
How many electrons can each shell hold?
1- 2 electrons
2- 8 electrons
3- 18 electrons
4- 32 electrons
What is an orbital?
A region of space within an atom that can hold up to 2 electrons with opposite spins
How are electrons removed?
From the highest occupied orbitals down removing 4s before 3d
How do you know what block each element is in from their electronic structure?
The block is what sub shell the outer electrons are in
What is meant by the term ionic bond?
Attraction between oppositely charged ions
What happens in ionic bonding?
A metal bonds with a non-metal due to the metal atom donating one or more electrons to the non-metal creating two ions
What is the shape of an ionic compound?
Giant ionic lattice
Why do ionic compounds have a high melting and boiling point?
Ionic bonds are strong due to the attraction between anions and cations
When does an ionic compounds conduct electricity and why?
Conducts when in a solution or molten but not when in solid phase
Moving charges are able to carry a current
Are ionic compounds soluble in polar solvents?
Yes due to the charged particles being attracted and separated by polar solvent particles
What is a covalent bond between?
Two non-metal atoms
What is expanding the octet and what can do that?
Expanding the octet is accepting more than eight electrons in the outer shell by using the empty d subshell to accommodate new electrons e.g. Sulphur Hexaflouride
What is reducing the octet and what can do this?
They can have less than eight electrons in the outer shell and gain stability through other means e.g. boron triflouride
What are lone pairs?
Non-bonding electron pairs that are not involved in covalent bonds
What is dative covalent bonding?
A lone pair being used to form a covalent bond for example in an ammonium ion
It is represented with an arrow in something form
What are the properties and structure of giant molecular compounds?
They have a giant covalent structure with very high melting points due to strong covalent bonds between carbon atoms for example diamond graphite and sulphur dioxide
They do not conduct electricity
What is the structure and properties of graphite
One layer of graphite which has three bonds for each carbon and one delocalised electrons which allows electricity to be conducted
Covalent bonds so high melting and boiling point
Weak intermolecular forces between layers of graphene
What is metallic bonding?
The attraction between metal cations and delocalised electrons
Why do metallic structures have high melting and boiling points?
As metallic bonds are strong due to the strong force of attraction
Do metallic compounds conduct electricity?
Yes due to the delocalised electron carrying a charge
What are the properties of metals?
The regular layers of atoms means that they are malleable and they are also good conductors of electricity and heat
What is the bonding structure and bond angle of a linear molecule?
180°
2 Bonding Pairs
0 Lone Pairs
What is the bonding structure and bond angle of a trigonal planar molecule?
120°
3 Bonding Pairs
0 Lone Pairs
What is the bonding structure and bond angle of a tetrahedral molecule?
109.5°
4 Bonding Pairs
0 Lone Pairs
What is the bonding structure and bond angle of a octahedral molecule?
90°
6 Bonding Pairs
0 Lone Pairs
What is the bonding structure and bond angle of a pyramidal molecule?
107°
3 Bonding Pairs
1 Lone Pairs
What is the bonding structure and bond angle of a angular/non-linear molecule?
104.5°
2 Bonding Pairs
2 Lone Pairs
What is electron pair repulsion theory?
Each pair of electrons will repel each other and the pairs will push part with equal pressure creating equal angles and structure
What is the rule on bonding angles with lone pairs?
Lone pairs repel bonding pairs more than they repel each other
What are intermolecular forces?
Attractive forces between neighbouring molecules caused by weak forces between very small areas of charged dipoles between molecules
What are london forces also called?
Induced Dipole-Dipole forces
How are london forces formed?
Electroms in an atom or molecule constantly move
At any instant there may be an uneven distrobution
This results in a temporary dipole
These dipoles induce dipoles in neighbouring molecule
These attract each other
What are the properties of london forces?
- Very weak
- Temporary forces which are constantly moving
- The more electrons (therefore the bigger the molecule) the stronger the london forces
What is electronegativity?
A measure of the attraction of an atom in a covalent molecule for the bonding pair of electrons
How is a polar bond formed?
A difference in electronegativities in a covalent bond
What are the properties of permanent-dipole-dipole bonds?
Stronger than induced dipole-dipole forces between similar molecules
London forces still exist
When do hydrogen bonds occur?
When hydrogen is bonded to Nitrogen Oxygen Flourine The hydrogen bond is between the lone pair on the nitrogen, oxygen or flourine and hydrogen and represented by a dotted line
What are hydrogen bonds?
Very strong permanent-dipole-dipole bonds from a very electronegative element bonding to hydrogen
What is the effect of hydrogen bonds?
- Water has a relatively high surface tension and viscosity
- Importangt in organic compounds containing O-H and N-H (alcohols and carboxylic acids)
- Responsible for shapes of proteins and DNA
- Ice floats on water due to ice’s diamond like structure and has a larger volume than liquid water giving it’s maximum density at 4°c