Bonds Flashcards
What is a covalent bond
Electrostatic attraction between the shared pair of electrons and the positive nuclei
Ionic bond
An electrostatic attraction between positive ions and negative ions
Metallic bond
An electrostatic attraction between positive ions and delocalised electrons
What happens in coordinate bonding
Both electrons are donated from 1 atom to the empty orbital of another
What is the shape of a simple molecule determined by
The electrons and bonds in it. This is because electron pairs repel each other and therefore try to get as far away as possible
Shapes of simple covalent molecules
2 pairs of electrons
Linear molecule
180 degrees
Shapes of simple covalent molecules
3 pairs of electrons
Trigonal planar
120 degrees
Shapes of simple covalent molecules
4 pairs of electrons
Tetrahedral
109.5 degrees
Shapes of simple covalent molecules
5 pairs of electrons
Trigonal bipyramidal
120 degrees & 90 degrees
Shapes of simple covalent molecules
6 pairs of electrons
Octahedral (8 faces)
90 degrees
What affects the shape of an atom
As well as bonding pairs of electrons repelling, any lone pairs that are around the central atom also affects the shape
What repels more lone pairs or bonding pairs
Lone pairs repel more
4 pairs of electron
3 bonding
1 lone pair
Pyramidal
107.5 degrees
4 pairs of electrons
2 bonding pairs, 2 lone pairs
( e.g. H20)
V - shaped / bent
104.5 degrees
5 pairs of electrons
4 bonding, 1 lone pair
Modified Trigonal bipyramid
5 pairs
3 bonding, 2 lone pairs
T shaped
6 pairs
4 bonding, 2 lone pairs
Square planar
How to determine the shape
1) group number of central atom
2) number of bonding atoms
3) charge
4) add up and divide by 2
5) work out lone pairs , total - bonding
What is electronegativity
The ability of an atom to attract the pair of electrons(/electron density) in a covalent bond towards itself
What would happen with Cl2 due to electronegativity
Nothing would happen because there is no difference in electronegativity, so we have a non-polar covalent bond
Ht would happen in HCL due to electronegativity
Chlorine is more electronegative that hydrogen , this is a polar bond
What does electronegativity depend on
- nucleus charge
- atomic radius
- electron shielding
What is the most electronegative element
F
Fluorine
How to increase electronegativity
More protons and a smaller radius increases attraction from the nucleus
What decreases electronegativity
More shielding decreases the attraction from the nucleus
What elements are relatively electronegative
N , nitrogen
O , oxygen
Cl , chlorine
where are intermolecular forces commonly found?
they exist between simple covalent molecules. these are the forces between individual molecules
what are they 3 types of IMF?
- van de Waals force (weakest)
- dipole-dipole force
- hydrogen bond ((strongest) but weak compared to real bonds)
how is a van der waals force formed?
electrons in an atom are unevenly distributed making a temporary dipole. this induces a dipole in the nearby atom. this creates an attraction between them
the affect of an atoms size on van der Waals forces
this bigger the Mr of the atom/molecule, the larger the van der Waal force is, which increases the boiling point
which atoms have van der Waals forces
all atoms and molecules have van der Waals forces
when does dipole-dipole forces occur
when the delta+ and the delta- in a molecule are permanent
how are the dipole-dipole forces formed
the delta+ end of one molecule attracts the delta- end of an adjacent molecule
what molecules can have dipole-dipole forces
asymmetric polar molecules as they have a net dipole moment
when would hydrogen bonds occur
only happens when hydrogen is bonded to a small electronegative atom with in a molecule
N, O, F
when drawing a hydrogen bond, what do you have to ensure
- all delta charges on involved atoms
- 180 degrees
- all lone pairs are on the diagram
