Unit 1 - Bonding Flashcards
What is a covalent bond?
A shared pair of electrons, between two positively charged nuclei.
Arrange ionic, polar, and pure bonds in a bonding continuum in order of increasing difference in electronegativity.
At the start, there’s pure covalent, zero difference.
In the middle, there’s polar covalent, low difference.
At the end, there’s ionic, high difference.
https://prnt.sc/LwOMDjHIssa6
What are the types of bonding & structure that can exist in elements?
Ionic Bonds
Pure Covalent Molecular
Polar Covalent Molecular
Covalent Network
Metallic
Draw a diagram to show metallic bonding, and describe why metals conduct electricity.
https://prnt.sc/1MCqQXfgozEI
(Positive metal ions interlaced with a sea of free moving electrons)
They can conduct, since electrons are delocalised, so they can move freely within the metal structure.
Describe a pure covalent bond, and provide an example.
Pure covalent bonds are covalent bonds that exist between two atoms with the same electronegativities.
Any of the diatomic molecules are good examples, e.g. H-H
Describe a polar covalent bond, and provide an example.
Polar covalent bonds form when a shaired pair of electrons are not shared equally, due to one element having a higher electronegativity than the other.
An example can be H - Br where H has an electronegativity of 2.2, and Br has an electronegativity of 3.0
Draw a molecule of HCl and label the partial charges present
https://prnt.sc/EGE0Gyx6JwZH
(Don’t need to draw the larger size of the other)
When will an ionic bond be formed?
When do they usually form?
Ionic bonds when there is a high enough difference in electronegativities, higher than polar covalent bonds.
They usually occur between metals and non-metals with high differences in electronegativities
e.g. Sodium chloride
How are ionic compounds held together and what type of structure will they have?
The electrostatic force of attraction between the oppositely charged ions in the lattice.
Which elements in the first 20 have a metallic structure?
Lithium, Beryllium, Sodium, Magnesium, Aluminium, Potassium, and Calcium.
Which elements in the first 20 have a covalent network structure?
Boron, Carbon (in the form of graphite, or diamond), Silicon.
Which elements in the first 20 have a covalent molecular structure?
Phosphorus, Sulfur, Fullerenes
How do London Dispersion Forces arise?
LDFs are caused by an uneven distribution of electrons within an atom.
This gives rise to temporary dipoles.
Which elements in the first 20 have a monatomic structure?
Noble Gases (Helium, Neon, Argon)
What happens to the strength of LDFs as the size of the atom/molecule increases?
Why does this happen?
Larger atoms and molecules exhibit stronger dispersion forces than smaller and lighter ones.
This is because, in a larger atom/molecule valence (outer) electrons are farther from the nucleui than smaller ones, they’re less tightly held so can form a temporary dipole easier.