Electrons, Bonding and Structure Flashcards
How many electrons can be in shell 1?
2
How many electrons can be in shell 2?
8
How many electrons can be in shell 3?
18
How many electrons can be in shell 4?
32
What is an electron shell?
Group of atomic orbitals with the same principle quantum number, n
What is n (principle quantum number)?
A number representing the overall energy level of the orbital.
What is an orbital?
A region of high probability within an atom that can hold up to 2 electrons with opposite spin
What does it mean if n (principle quantum number) is bigger?
The bigger the number, the further the distance between the energy level and atomic nucleus
How man electrons do orbitals hold?
2
What must electrons in the same orbital have?
Opposite spin
What are the 4 orbitals?
S-orbital
P-orbital
D-orbital
F-orbital
Where is s-orbital present?
n=1 upwards
Where is p-orbital present?
n=2 upwards
Where is d-orbital present?
n=3 upwards
Where is f-orbital present?
n=4 upwards
How many s-orbitals does a shell contain?
1
How many p-orbitals does a shell contain?
3
How many d-orbitals does a shell contain?
5
How many f-orbitals does a shell contain?
7
What is the shape of a s-orbital?
Sphere
What is the shape of a p-orbital?
Dumbbell
What is the order that you fill orbitals?
1s 2s 2p 3s 3p 4s 3d 4p
What are the two exceptions when it comes to filling orbitals?
Cu
Cr
What does Cu do?
1s2 2s2 2p6 3s2 3p6 4s1 3d10
What does Cr do?
1s2 2s2 2p6 3s2 3p6 4s1 3d5
What do CU and Cr do this?
Because they can become stable from full and half full 3d sub shells
How can you shorten filling orbitals?
By using the noble gases
What are the three noble gases that you can use?
He 1s2
Ne 1s2 2s2 2p6
Ar 1s2 2s2 2p6 3s2 3p6
What is a lattice?
A regular repeated three dimensional arrangement of atoms, ions or molecules in a metal or other crystalline solid
What is ionic bonding?
Ions of opposite charge held together by electrostatic attraction
What is ionic bonding between?
Metal and non metal
What are the properties of ionic bonding?
High melting and boiling points
Can conduct in liquid/aqueous state but not in a solid state
Soluble in polar solvents
Why does it have high meting and boiling points?
Because a large amount of energy is needed to overcome strong electrostatic attraction
Why is the melting point higher in certain ionic bonds?
Greater ionic charge in lattice = higher melting point
What must happen for ionic bonds to dissolve in polar solvents?
Ionic lattice must be broken down
Water molecules must attract and surround the lattice
What is an example of a polar solvent?
Water
What does solubility depend on in ionic bonding?
An attraction between the ions and water molecules
What happens as the ionic charge increases?
The solubility decreases
Why can ionic bonds conduct electricity when liquid or molten?
Because ions are free to move therefore there is charge carries so it can conduct electricity
Why can’t sometimes ionic bonds be dissolved in water?
Because the ionic attraction is too strong
What is covalent bonding?
Atoms that share a pair of electrons held together by intermolecular forces
What is it called when a pair of electrons aren’t shared with the other element?
Lone pair
What is it called when a covalent bond does that have a full amount of electrons?
Electron defieicent
What is an example of an electron deficient covalent bond?
Borontrifluoride BF3
What rule is broken when a covalent bond is electron deficient?
Octet rule
When is it okay for the octet rule to be broken?
When there is more than 8 electrons in the covalent bond because the 3rd shell can hold 18
What is a dative bond?
A bond formed when both electrons in the share are donated by one atom
What is an example of a dative bond?
When ammonia acts as a base and reacts with H+ so donates both its electrons to the H+ to form ammonium
When drawing covalent ions what do you represent the extra electron as?
A little triangle
What are the properties of covalent bonding?
Low melting and boiling points
Insoluble in polar solvents
Doesn’t conduct electricity
Why does covalent bonds have a low melting and boiling points?
Small covalent molecules
Weak intermolecular forces
Why are covalent bonds insoluble in polar solvents but are in non-polar solvents?
Because london forces form between the solvent and the molecules
Why does covalent bonds not conduct electricity?
Because there is no mobile charges so no charge carries so can’t conduct
What is the VSEPR Theory?
The shape of a molecule/ion is determined by the no. of electron pairs in the outer shell of the central atom, repelling as far away as possible
What does VSEPR stand for?
Valence Shell Electron Pair Repulsion
What shape is formed when there is two regions?
Linear
What is the bond angle of a linear molecule?
180 degrees
What is the shape formed when there is three regions>/
Trigonal planar
What is the bond angle of a trigonal planar molecule?
120 degrees
What shape is formed when there is four regions?
Tetrahedron
What is the bond angle of a tetrahedron molecule?
109.5 degrees
What shape is formed when there is six regions?
Octahedron
What is the bond angle of an octahedron molecule?
90 degrees
What is the shape formed when there is 5 regions?
Trigonal bi-pyramid
What is the bond angles of a trigonal bi-pyramid?
90 and 120 degrees
What shape is formed when there is 3 bonding pairs and 1 lone pair?
Pyramidal
What shape would you think it would be there was 3 BP and 1 LP and why does this shape not form?
Tetrahedron as there is 4 electron pairs
But the lone pair aren’t attracted to the nuclei so they repel a further 2.5 degrees
What is the bond angle of a pyramidal molecule?
107 degrees
Why doe lone pairs have a greater repulsion?
Because there aren’t attracted to the nuclei
How much does lone pairs reduce the bond angle by?
2.5 degrees
What shape is formed when there is 2 bonding pairs and 2 lone pairs?
Non-linear
What is the bond angle of a non-linear molecule?
104.5 degrees
What is electronegativity?
A measure of the tendency of an atom to attract a bonding pair of electrons within a covalent bond
What happens to electronegativity across a period?
It increases
Why does electronegativity increase across a period?
Nuclear charge increases so there is a greater nuclear attraction so electronegativity increases
What happens to electronegativity down a group?
It decreases
Why does electronegativity decrease down a group?
The size of the atom increases so shielding of the outer shell increases so nuclear attraction reduces so electronegativity decreases
What happens in a bond between different atoms when one element is more electronegative?
The electrons will attracts towards the more electronegative element
Will have a S- charge
What happens to the other element in the bond when the other is more electronegative?
It will lose a small amount of electron density
Will have a S+ charge
What is S-?
A (slight charge) delta
When are molecules polar?
When the dipoles are in the same direction
When are molecules non-polar?
When dipoles are symmetrical (opposite direction) so they cancel each other out
What does it mean when there is no difference between electronegativity?
It is a non-polar covalent bond
What does it mean when there is a small difference between electronegativity?
It is a polar covalent bond
What does it mean when there is a large difference between electronegativity?
It is an ionic bond
What is the size of a small difference?
0-1.8
What is the size of a large difference?
> 1.8
What are intra-molecular forces?
Strong bonds inside of molecules
What are intermolecular forces?
Forces that act between different molecules and are much weaker than covalent bonds
What are the three types of forces and their relative strength?
London forces - 1
Hydrogen forces - 50
Permanent dipole-dipole - 10
What is a dipole-dipole force?
A weak attractive force between permanent dipoles in neighbouring polar molecules
Where does dipole-dipole happen?
Attraction between two delta charges of elements
How do london forces work?
Moving electrons = changing dipole
Instantaneous dipole induces dipole on neighbouring molecule
Induced dipole induces further dipole
They attract each other
What happens to london forces as the no.of electrons increase?
Strength of london forces increase due to the larger instantaneous dipole created
What are the anomalous properties of water?
Elevated melting + boiling point Ice floats (solid is less dense than the liquid)
Why does water have an elevated boiling + melting point?
Because of strong hydrogen bonds
Why does ice float?
Because when water freezes its molecules arrange themselves in a “more open, regular, lattice structure”
Where does the hydrogen bond form?
Between the S+ and S- of two dipoles
What are you doing when you’re boiling/melting water?
Breaking the hydrogen bonds
When can hydrogen bonding only happen?
When hydrogen is covalently bonded to fluorine, nitrogen or oxygen
