Topic 2 - Bonding And Structure Flashcards
(21 cards)
Ionic Bonding
Ionic compounds are…
Oppositely charged ions held together by electrostatic attractions
Most ionic compounds dissolve in water because…
Water molecules are polar
Ionic compounds can conduct electricity when molten or dissolved in solution because…
The ions are free to move around
Ionic compounds have high melting points because…
There are many strong electrostatic forces between oppositely charged ions
Ionic compounds are brittle because…
When struck, the layers slide and you get +ve ions aligned with +ve ions and -ve ions aligned with -ve ions. They repel and the structure breaks apart.
High charge density is when…
A small ion has a high charge. This results in a stronger electrostatic attraction and higher melting point.
With ionic radius, as you go down a group it…
Increases due to the increase in the number of electron shells.
As the atomic number increases, the ionic radius of isoelectric ions…
Decreases because there is a greater nuclear charge experienced by the same number of electrons, so the attraction between the nucleus and the orbiting electrons goes up.
Covalent Bonding
Covalent bonding is the…
Sharing of electrons in order for atoms to obtain a full shell. There is electrostatic attraction between the shared electrons and the +ve nucleus.
A dative covalent bond is…
A covalent bond in which both electrons in the shared pair are provided by one atom.
Bond enthalpy is linked to…
The length of the bond. The shorter the bond the higher the bond enthalpy.
Metallic Bonding
+ve ions are formed as…
Metals donate electrons to form a ‘sea’ of delocalised electrons. This creates an electrostatic attraction.
Electronegativity increases as…
You go from left to right across a period and up a group. Fluorine is the most electronegative.
F > O > Cl = N > C > H
The bigger the difference in electronegativity…
A difference of zero in electronegativity…
The more ionic the compound will be, and more polar the bond will be.
Will be purely covalent, with non-polar bonds.
Intermolecular Forces
London forces exists between…
Atoms and molecules
The bigger the molecule or atom, the more London forces as…
You have larger electron clouds.
More electrons = stronger/more London forces
When boiling or heating, we are breaking the…
Weak London forces NOT covalent bonds.
Branched hydrocarbons have weaker London forces than straight chain hydrocarbons because…
They can’t pack together as close and there are fewer points of contact with other molecules.
Permanent dipole - dipole exists in…
Molecules with a polarity.
Hydrogen bonding occurs when…
You have very electronegative elements.
Hydrogen on one molecule forms a bond with the lone pair on nitrogen, oxygen or fluorine (3 most electronegative).
Why are alcohols not as volatile as alkanes?
Due to the hydrogen bonds it has compared to the weaker London forces alkanes have.
