Bonding Flashcards
GCSE bonding types are all…? What does this mean?
They are all intramolecular, meaning that they are between atoms in a molecule.
Which one is smaller - cations or anions? Why?
Cations are smaller due to having a reduced amount of electrons. The nuclear charge of the atom remains the same, just with decreased electrons - this means that the remaining electrons have a much higher force of attraction towards the nucleus. This causes atomic radius to decrease.
What happens to ionic bonds as charges increase?
Increase in strength - more electrons means a higher electrostatic force. A lot of thermal energy is needed to break these bonds BUT YOU DO NOT BREAK IONIC BONDS WHEN MELTING/BOILING
How many electrons can a metal easily lose?
3.
How are covalent bonds held together?
Combination of attractive and repulsive forces. The shared electrons are electrostatically attracted to the positive nucleus of each atom in the bond.
What are co-ordinate/dative bonds and what is an example of this?
Type of covalent bond where both electrons in the shared pair come from just one of the included atoms. An example of this is between a base (H+ acceptor) and an acid (H+ donator).
What happens to metals with higher numbers of electrons?
More electrons = stronger pull on electrons in the delocalised ‘sea’.
As metals increase in ionic charge, size decreases as melting/boiling point increases.
What is electronegativity?
The tendency of an atom to attract electrons to itself. Atoms with a smaller atomic radius have high nuclear charge and therefore have high electronegativity.
E.g. H-H bond both atoms have the same charge so electrons are equally shared between them. However, in a H-F bond, the share of electrons isn’t even as F has a higher nuclear charge and will have a greater share.
Describe London Dispersion Forces.
Occurs between molecules with equal electronegativity. Electrons are temporarily in the same place, causing the molecule to have a positive and a negative pole (dipoles). The positive pole of one molecule attracts electrons from another, causing a chain reaction. Here, we say that the 1st molecule has induced the neighbouring molecule.
This dipole-dipole bond isn’t very strong because it is temporary.
Explain permanent dipole-dipole bonds.
Occurs when molecules are polar, meaning that there is an unequal sharing of electrons in a bond (i.e. one atom is more electronegative). These molecules are permanently partially charged because the positive pole is attracted to the negative pole.
This dipole-dipole bond is stronger than LDF bonds because they are permanent.
Explain hydrogen bonds.
Special type of PDD. Hydrogen must be bonded with fluorine, oxygen or nitrogen (FON - Freaks Of Nature, because the bond is stronger than it should be). These are called hydrides and are highly electronegative.
These are the strongest type of intermolecular bond because the molecules are highly polarised. FON atoms have a much greater share of electrons than H.
Why are ionic compounds usually solid at room temperature?
They have strong electrostatic forces of attraction between the ions, forming a lattice. These require a lot of energy to overcome and move the ions apart.
Why are ionic compounds brittle?
Applying pressure shifts the alignments of the ions.
What is the trend in melting points down group 7?
Increase because more electrons mean stronger London Dispersion Forces.
