Structure and bonding Flashcards
What are covalent bonds
Non metals, shared pair of electrons
Covalent bonds are formed between non-metal atoms that are bonded by a shared pair of electrons and the positive nuclei of each atom are held together by their common attraction for the shared electrons.
What are pure covalent bonds
When 2 atoms share bonding equally, it is known as pure covalent bonding. This is because they have the same attraction for the bonding electrons - both atoms have the same electronegativity value
What is polar covalent bonding
Most covalent compounds have different electronegativities between elements, this means that one atom has a greater attraction for the bonding electrons will have a slightly negative charge leaving the other atom with a slightly positive charge.
A permanent dipole is thus formed, bonding in which there is a permanent dipole is known as polar covalent bonding.
As a general rule, if the difference in electronegativity is ??? than ??? the bond is covalent
less than 2
definition of covalent bond
A covalent bond is a shared pair of electrons, electrostatically attracted to the positive nuclei of two atoms
definition of ionic bonding
The ionic bond is the electrostatic force of attraction between a metal ion and a non-metal ion.
An electronegativity difference ??? than ??? is generally ionic
more than 2
explain what is meant by the bonding continuum
The bonding continuum is used to understand different types of bonding by observing variations in electronegativity between atoms. 5. The difference in electronegativities between bonded atoms gives an indication of the ionic character. The larger the difference, the more polar the bond will be.
Are van der Waals intra or inter - molecular
intermolecular
the intermolecular forces acting between molecules are known as
van der Waals
what are the van der Waals
LDFs, permanent dipole - permanent dipole interaction, hydrogen bonding
Carbond dioxide and tetrachloromethane are non polar due to …..
symmetry
What is the weakest van der Waals
LDFs
permanent dipole - permanent dipole interactions occur between
between polar molecules
Are PD - PD interactions strong or weak
while stronger than LDFs they are still weak
Which has higher mpts and bpts
Why?
polar substances are higher mpts and bpts
PD - PD interactions are stronger than LDFs for molecules with similar no. of electrons. This results in polar substances having higher mpts and bpts than non- polar of similar electron no.
How can you tell if a substance is polar or non-polar experimentally
setting up burettes for each substance, place above beaker. Take a charged rod and when you open the burette for the substance to flow through holding it near the substance will either have no effect or cause the stream of liquid to bend towards the charged rod
Polar substances such as water are attracted to a charged plastic rod but non-polar substances like heptane are not attracted.
Describe Hydrogen bonding
When hydrogen is bonded to the highly electronegative elements fluorine, oxygen and nitrogen, it results in the electrons in the bond being more strongly attracted away from the hydrogen atom. The hydrogen atom is so small that the positive charge on the atom is unusually high and the bond is highly polar . This results in very strong PD-PD interaction between molecules called a hydrogen bond
what is the strongest van der Waal
Hydrogen bonding
are hydrogen bonds stronger or weaker than covalent bonds
weaker
what is the viscosity
the thickness
what is volatility
a material quality which describes how readily a substance vaporizes
if a liquid only has weak LDFs holding it together will it be very or not very viscous
not very viscous
What type of compounds will be the most viscous
compounds which are highly polar and/or more hydrogen bonding present
What are the key features which need to be considered in order to predict solubility?
- the presence of hydrogen bonding
- whether the shape of a molecule makes it polar
How do non-polar molecules dissolve other non-polar molecules
by forming LDFs between the molecules
Why can non-polar substances like fats and oils not dissolve in water
cannot form strong intermoecular forces of attraction with water, and therefore are not dispersed throughout the water like soluble polar covalent and ionic substances
Define miscibility
the ability of liquids to mix in all proportions, forming a solution. Water and ethanol, for example, are miscible and this forms the basis for alcoholic drinks.
