Bonding and Structure Flashcards
Define ionic bond
A strong electrostatic force of attraction between oppositely charged ions
Define giant ionic lattices
A regular repeating pattern of oppositely charged ions
What is the mpt and bpt of ionic compounds, state why
Mpt and bpt are very high because a lot of energy is needed to overcome the strong electrostatic force of attraction between oppositely charged ions
Can ionic compounds conduct electricity when they are a solid , state why
Ionic compounds cannot conduct electricity when solid because the ions are not free to move, they are fixed in position in the lattice
Can ionic compounds conduct electricity when they are molten or in solution, state why
Ionic compounds do conduct electricity when molten or in solution because the ions can move as the lattice has broken down
Are ionic compounds soluble
Yes, because water is polar. Water molecules attract the oppositely charged ions causing the lattice to break down
Define covalent bond
The strong electrostatic force of attraction between shared pair of electrons and the nuclei of the bonded atoms
Define dative covalent bond
Are covalent bonds which are formed when both electrons are donated by only one of the atoms in the bond
What do we need to consider when determining the shape of a molecule
- The number and type of electron pairs around the central atom
- Electron pairs repel each other, as far away as possible
- Lone pairs repel more then bonded pairs
What is the shape and bond angle of a molecule with two bonded pairs and 0 lone pairs
Shape = Linear
Bond angle = 180
What is the shape and bond angle of a molecule with 3 bonded pairs and 0 lone pairs
Shape = Trigonal planar
Bond angle = 120
What is the shape and bond angle of a molecule with 4 bonded pairs and 0 lone pairs
Shape = Tetrahedal
Bond angle = 109.5
What is the shape and bond angle of a molecule with 3 bonded pairs and 1 lone pair
Shape = Pyramidal
Bond angle = 107
What is the shape and bond angle of a molecule with 2 bonded pairs and 2 lone pairs
Shape = Non-linear
Bond angle = 104.5
Define electronegativity
The ability of an atom to attract electrons to itself in a covalent bond
What elements have a higher electronegativity
- Nitrogen
- Oxygen
- Fluorine
- Chlorine
- Bromine
Define non-polar
The electrons are shared equally between the 2 atoms because the atoms have the same( or very similar) electronegativity
Define polar
The electrons are shared unequally because one atom has a greater electronegegativity then the other one
Define induced dipole dipole intermolecular forces
The weakest inteolecular force of attraction occurring between all molecules and non-polar molecules
Define permanent dipole dipole
Slightly stronger intermolecular force of attraction between polar molecules
Define hydrogen bonding
Strongest intermolecular force of attraction occurring between hydrogen bonded to F or O or N and a lone pair of electrons
Describe how induced dipole dipole forces are made
. At any moment in time the electrons in an atom/ molecule are unevenly distributed
. This creates a temporary ( instantaneous) dipole
. This induces an induce dipole in the neighbouring molecule/ atom
. The two dipoles attracted each other- This is the weakest force of attraction
Describe how permanent dipole dipole are made
. These are the attraction between the delta positive and delta negative ends of two polar bonds
. These attractions exist when molecules are polar- when one arom has a higher electronegativity then the other one
Describe how hydrogen bonds are made
. Hydrogen bonding occurs when a hydrogen atom is directly bonded to fluorine, oxygen or nitrogen only
. There must be a lone pair of electrons
What are the anomalous properties of water
1) water has a relatively high mpt and bpt. This is because when water melts/boils the hydrogen bonds are broken. Hydrogen bonds are the strongest intermolecular forces of attraction and so require a lot of energy to overcome them, hence a higher then expected mpt/bpt
2) When water forms ice it takes the form of a open lattice structure- this results in ice being less dense then water. This is because the hydrogen bonds hold the water molecules further apart in an open lattice structure in ice. This means that the density of ice is less then the density of liquid water
Define a simple molecular lattice
A 3D structure of molecules held together by weak intermolecular forces
What are the physical properties of simple molecular lattices
. Low mpt/bpt because little energy is needed to break the weak intermolecular forces
. Electrical conductivity- non-conductors because the electrons are localised in bonds and not mobile
. Soluble in non-polar solvents as induced dipole dipole forces will form between the structures and the sovent. Insoluble in polar water
Define giant covalent lattices
Is a 3D structure of atoms, all bonded together by strong covalent bonds
Properties of giant covalent structure
. High mpt because all atoms are held together by strong covalent bonds which require a lot of energy to break
. Non- conductors of electricity because all electrons are localised in bonds
. Graphite conducts electricity because each carbon has 1 electron which is delocalised and can move to carry a charge
. Insoluble in all solvents because each atom is bonded to every other atom by strong covalent bonds. Atoms cannot interact with solvent molecules
Define metallic bonding
Strong electrostatic attraction between the delocalised sea of electrons and the positive ions
Compare group 3 and group 1 metals
Group 3 metals will have more delocalised electrons in the sea then group 1
properties metals
. Conductivity- metals conduct electricity and heat because the delocalised electrons are free to move
. Mpt/ Bpt- high mpt/ bpt because alot of energy is required to overcome the strong electrostatic forces of attraction between the sea of delocalised electrons and the positive ions
Compare the properties of group 3 and group 1 metals
. Conductivity- group 3 metals will have a higher conductivity because there are more valence electrons so more electrons can move in the delocalised sea which can move
. Mpt/Bpt- group 3 metals will have a higher mpt/bpt because there is a stronger attraction between the smaller and more highly charged cations and the delocalised sea of electrons
