Unit 1: KA2 Structure and bonding Flashcards
Elements are held together in different ways and the properties of chemical compounds are determined by the bonding between atoms and the attractive intermolecular forces between molecules.
What do atoms share in covalent bonds?
Pairs of electrons.
Describe COVALENT BONDING.
When two positive nuclei are held together by their common attraction for the shared pair of electrons.
*an example of an intramolecular force
When are POLAR COVALENT bonds formed?
When the attraction of the atoms for the pair of bonding electrons is different.
Delta positive (δ⁺ or 𝛿⁺) and delta negative (δ⁻ or 𝛿⁻) notation can be used to indicate…
The partial charges on atoms, which give rise to a dipole.
How can ionic formulae be written?
By giving the simplest ratio of each type of ion in the substance.
Describe IONIC BONDING.
The electrostatic attraction between positive and negative ions.
What structure do ionic compounds form?
Ionic compounds form lattice structures of oppositely charged ions.
PURE COVALENT bonding (non-polar bonding) and IONIC bonding can be considered as…
Opposite ends of a BONDING CONTINUUM.
What (type of bonding) lies in the middle of the BONDING CONTINUUM?
POLAR COVALENT bonding.
What does the difference in electronegativities between bonded atoms indicate?
The ionic character.
The smaller the difference in electronegativities between bonded atoms, the more polar the bond will be. True or False.
False, the BIGGER the difference in electronegativity, the more polar the bond will be.
If the difference in electronegativities is LARGE, then the movement of bonding electrons from the element of lower electronegativity to the element of higher electronegativity is complete, resulting in the formation of ions. True or False?
*Feel free to rephrase
True
*LARGE DIFFERENCE in electronegativities = bonding electrons from lower electronegativity go to higher electronegativity = forms ions.
Compounds formed between metals and non-metals are often, but not always —–.
IONIC.
Physical properties of a compound should be used to deduce the type of bonding and structure in the compound. Name the physical properties you should refer to. [5 marks]
State at room temperature [1],
Melting point [1],
Boiling point [1],
Solubility [1],
Electrical conductivity [1].
All molecular elements and compounds, and monatomic elements condense and freeze at sufficiently low temperatures. What must exist between the molecules or discrete atoms for this to occur?
At least one form of attractive force.
Intermolecular forces acting between molecules are known as…
van der Waals forces.
There are several different types of van der Waals forces. Name the 3 forces we focus on in Higher Chemistry. [3 marks]
London dispersion forces [1],
AND
permanent dipole-permanent dipole interactions [1] that include hydrogen bonding [1].
London dispersion forces are forces of attraction that can only operate between a few atoms and molecules. True or False?
False. They can operate between ALL atoms and molecules.
London dispersion forces are much STRONGER/WEAKER than all other types of bonding.
What does the strength of London dispersion forces relate to?
WEAKER.
The STRENGTH of London dispersion forces is related to the NUMBER OF ELECTRONS within an atom or molecule.
How are London dispersion forces formed?
As a result of electrostatic attraction between dipoles (both temporary and induced –> caused by the movement of electrons in atoms and molecules.)
A molecule is described as POLAR if it has a ——— ——.
The spatial arrangement of polar covalent bonds can result in a molecule being polar. True or False?
PERMANENT DIPOLE.
True.
Besides London dispersion forces, what are additional electrostatic forces of attraction between polar molecules?
Permanent dipole-permanent dipole interactions.
Which is the stronger force of attraction for molecules with similar numbers of electrons? Permanent dipole-permanent dipole interactions OR London dispersion forces.
Permanent dipole-permanent dipole interactions are stronger.
Bonds consisting of a hydrogen atom bonded to an atom of a strongly electronegative element such as fluorine, oxygen or nitrogen are HIGHLY —–.
POLAR.