Physical Chemistry- Bonding Flashcards
Define a metallic bond
Attraction between delocalised outer shell electrons and positive metal ions
How are metals arranged?
Regular arrangement
Giant metallic lattice- (giant=endlessly repeating)
Define an ionic bond
Strong electrostatic attraction between oppositely charged ions
Define a covalent bond
A shared pair of electrons
What is a lone pair?
Pair of electrons that are not bonded
Define coordinate bonds
A covalent bond in which the shared pair of electrons come from the same atom.
NH3 + H -> NH4
How are coordinate bonds represented?
A line with an arrow in the middle
What is the electron repulsion theory?
lone pair- lone pair > lone pair- bonded pair > bonded pair-bonded pair
How much does the lone pair repel the bond angle?
By 2.5 degrees
Define electronegativity
The power of an atom to attract the pair of electrons in a covalent bond
What happens to electronegativity as you go across a period?
Increases
Nuclear charge increases
What happens to electronegativity as you go down a group?
Decreases
Atomic radius increases
Shielding increases
What is the most electronegative element?
Fluorine
Define a polar bond
Uneven distribution of electrons
Describe a polar bond in terms of electronegativity
Uneven electronegativity so bonded electrons are attracted to the more electronegative element
Dipole has formed
Describe an ionic bond in terms of electronegativity
Large difference in electronegativity
Electrons have been pulled so far enough towards the more electronegative atom that they have been lost and have formed ions
Electronegativity between C-H
Similar electronegativity so it is non-polar
What are the three types of intermolecular forces?
Van der Waals
Permanent dipole-dipole
Hydrogen bonds
When do Van der Waals forces act?
Occurs in all substances
When do permanent dipole-dipole forces act?
Between molecules with a permanent dipole
When do hydrogen forces act?
Between O-H, N-H, F-H
How are Van der Waals forces created?
Caused by an instantaneous dipole due to the constant movement of electrons
This induces a dipole in other molecules resulting in a very weak force of attraction
How do VdW forces increase?
Bigger molecules have bigger a Mr = more electrons = induced dipole is larger
What do hydrogen bonds form between?
Hydrogen and lone pair of electrons on O,N or F
Properties of substances with hydrogen bonding
High melting/boiling points due to the strength of hydrogen bonds
Soluble because it forms hydrogen bonds with water
