Topic 2 - Bonding and Structure I Flashcards
Definition of Metallic Bonding
A metallic bond is the electrostatic force of attraction between positive metal ions and the delocalised electrons.
Melting Points of Metallic Bonding
Metals have a high melting point due to the strong electrostaic forces between the positive ions and the sea of delocalised electrons. This requires a lot of energy to overcome.
Trend in melting points for metallic bonding
Metallic bonding gets stronger because in Mg there are mroe electrons in the outer shell that are being released to the sea of electrons. The Mg ion is also smaller and has one mroe proton. Therefore there is a stronger electrostatic attraction between the positive metal ions and the delocalised electrons and higher energy is needed to break bonds.
Conductivity of Metals
All metals conduct electricity when molten and when solid. The sea of delocalised electrons is moblile and moves through the lattice of metal ions.
Malleabillity of Metals
Metals are malleable because the positive ions in the lattice are all identical. So therefore the planes of ions can easily slide over eachother.
Definition of ionic bonding
An ionic bond is the strong electrostatic force of atraction between oppositely charged ions formed by electron transfer.
Conductivity of Ionic
Cannot conduct in solid state as ions are fixed.
Conducts in molten state as ions are free moving.
Melting points of ionic solids
Depends on ion-ion forces.
Ions with small radius give stronger forces of attraction.
Brittle nature of ionics
Little force allows the ions be next to similar ions, this will add a force of repulsion.
Covalent Bond Definition
A covalent bond is strong ans is caused by electrostatic attraction between the bonding shared pair of electrons and the two nuclei.
Effect of multi bonds on bond strength and length
Nuclei joined by multiple bonds have a greater electron density. This causes an greater force of attraction between the nuclei and the electrons between them, resulting in a shorter bond length and greater strength.
Definition of a dative bond
A dative bond forms when the shared pair of electrons in the covelant bond come from only one of the bonding atoms.
Shapes of Molecules
Linear: 2,0, 180 Trigonal Planar: 3, , 120 Tetrahedral: 4,0, 109.5 Trigonal pyramidal: 3,1 107 Bent, 2,2 104.5 Trigonal Bipyramidal 5,0 120 and 90 Octahedral 6,0 90
Electronegativety definition
Electronegativity is the relative tendency of an atom in a covalent bond in a molecule to attract electrons in a covalent bond to itself.
Factors affecting electronegativity
Across the group, the atomic radius decreases as the number of protons in the atom increases. Therefore the electronegativity increases.
Down the group, the atomic radius increases and the shielding increases, Therefore the electronegativity decreases.
How are polar bonds made?
A polar bond forms when the elements in the bond have diffrent electronegativities. It has an unequal distribution of electrons producing a charge seperation.
Polar and non polar molecules
Indicidual dipoles on the bonds cancel out due to symmetrical shape of molecule. The molecule is non polar.
How are London Forces made?
Electrons in a covalent molecule oscillate within thier atomic orbitals or covalent bonds.
The density can fluctuate and parts may become more negative.
These tempoary diapoles can form diapoles in neighbouring molecules.
Factors affecting size of London Force
More electrons mean a higher chance of diapole forming making the London Forces stronger.
The shape of the m,olecule can also have3 an effect on the size of the London forces. Long straight chain alkanes have a larger surface area on contact with the molecules.
Hydrogen bonding
Happens between hydrogen atoms and one of the three most electronegative atoms which must have an avalible lone pair of electrons.
Ionic substances dissovling in water
Ionic lattice dissovles by breaking up the bonds between metal ions and water molecules.
The negative ions are attracted to the delta positive hydrogen and the positive ions are attacted tot he delta negative oxygen.
Solubility of alcohol
Smaller alcohols can form hydrogen bonds in water
The longer the chain the less soluble it becomes.
