Topic 2 - Bonding And Structure Flashcards
Explain ionic bonding?
lonic bonding occurs between a metal and a non-metal. Electrons are transferred from the metal to the non-metal to form full outer shells.
Transfer of electrons creates charged particles called ions. Oppositely charged ions attract through electrostatic forces to form a giant ionic lattice.
Explain the link between the charge of an ion and the strength of an ionic bond?
The charge of an ion is related to the strength of the ionic bond that forms. lons with a greater charge will have a greater attraction to the other ions resulting in stronger forces of attraction and therefore stronger ionic bonding.
Explain link between ionic radius and ionic attraction?
Larger ions that have a greater ionic radius will have a weaker attraction to the oppositely charged ion because the attractive forces have to act over a greater distance.
What forms polar molecules?
Polar molecules arise when there is an overall difference in polarity across the molecule, due to the arrangement of polar bonds and the geometry of the molecule. Polar molecules must have polar bonds.
What are Van der Waals forces?
Van der Waals forces are the weakest type of intermolecular force. They act as an induced dipole between molecules. They are also called London forces or instantaneous dipole-induced forces.
What affects the strength of Van der Waals forces?
The strength of van der waals forces varies depending on the Mr of the molecule and its shape.
The greater the Mr of the molecule, the stronger the intermolecular forces.
What is link between shape of molecules and strength of Van der Waals forces?
Straight chain molecules experience stronger van der waals forces than branched-chain molecules as they can pack much closer together. This reduces the distance over which the force acts, making the intermolecular force stronger.
What is link between boiling point and alkane chains?
As the chain length of the alkane increases, so does the Mr of the molecule. This results in stronger intermolecular forces between the chains, and so the compound has a higher boiling point as a result.
What is a permanent dipole?
If the two atoms that are bonded have sufficiently different electronegativities, a polar bond forms. The more electronegative atom draws more of the negative charge towards itself and away from the other atom, producing a 2- region and a 2+ region. This produces a permanent dipole.
Explain hydrogen bonds are made of?
Hydrogen bonding is the strongest type of intermolecular force. Hydrogen bonds only act between hydrogen and the three most electronegative atoms: nitrogen, oxygen and fluorine.
How are hydrogen bonds formed?
nitrogen, oxygen and fluorine.
The lone pair on these atoms form a bond with a 1+ hydrogen atom from another molecule, shown with a dotted line
What are the properties of a molecule held together by hydrogen bonding?
Molecules held together with hydrogen bonds have much higher melting and boiling points compared to similar-sized molecules without hydrogen bonding.
Why do alcohols have such high boiling points?
This is because the lone electron pair on the oxygen atom is able to form hydrogen bonds with a hydrogen on another alcohol molecule.
Why is water a popular choice of solvent?
Its hydrogen bonding capabilities allow it to dissolve some ionic compounds by solvating the individual ions, and to dissolve some alcohols by forming hydrogen bonds with their hydroxyl group.
When are non aqueous solvents used?
Non-aqueous solvents are often used for compounds which have the same type of intermolecular force.
