Bonding and Structure
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What is an ionic bond?
The electrostatic force of attraction between positively and negatively charged ions.
What are the properties of ionic compunds?
1.Can’t conduct electricity when solid as the strong ionic bonds hold the charges in place. When molten or aqeous the delocalised electrons are free to move so ionic compounds can conduct electricity. 2.High melting and boiling point due to strong electrostatic forces of reaction 3.Regular structure 4.Giant repeating structure 4.Dissolve in water (polar)
What is a covalent bond?
The electrostatic forces of attraction between two neuclei of two atoms and the shared electrons.
What is a dative covalent or coordinate bond?
Where one atom donates 2 electrons to an atom or ion for form a bond. An example is Nitrogen in ammonium (NH4+). H+ is electron deficient, so has space foe 2 e- in its shell which are provided by Nitrogen.
Why do molecules have specific shapes with specific angles?
Because the bonds repel each other equally. Bonds contain electrons which want to be as far apart as possible
Why do lone pairs repel each other more than bonded pairs?
Because bonded pairs are further away from the nucleus due to being in a bond with another atom. Lone pairs only exist around one atom so are closer and repel each other more. This repulsion gives rise to different shapes.
How to determine shape of a molecule?
Number of bonded and lone pairs
What is the shape of an atom with one bond and no lone pairs?
Linear HCL
2 bonds no lone pairs
Linear, 180 degrees eg CO2
2 bonds 2 lone pairs
Bent. 104.5 degrees3 eg H20
3 bond pairs 0 lone pairs
Trigonal Planar 120 degrees BH3
3 bonded pair one lone pair
Pyramidal 107 degrees NH3
4 bonded pairs no lone pairs
Tetrahedral 109.5 degrees
5 bond pairs 0 lone pairs
trigonal bipyramidal 90 and 180 degrees
6 bond pairs 0 lone pairs
Octahedral 90 degrees
What is electronegativity?
The ability of an atom to attract the electrons in a covalent bond. (They spend more time around the more electronegative atom, making it slightly more negative).
How does electronegativity increase along the periodic table?
It increases the further right and up you go
What is the most electronegative element and elements?
Flourine, Oxygen, Chlorine
What is a polar bond?
The uneven distribution of electrons in a bond due to difference in electronegativity.
What is a dipole?
The difference in charges of atoms in a molecule due to bond polarity.
How can you get polar bonds but a non-polar molecule?
The polar bonds are symmetrical so cancel each other out, so the whole molecule has no overall polarity.
What is a permanent dipole-dipole interaction?
When the permanent dipole of one molecule interacts with the permanent dipole of another molecule. Eg water molecules interacting.
What is an instantaneous dipole?
The moment where there is a difference in charge of atoms in a bond due to the random movement and distribution of electrons within that bond.
What is an induced dipole?
A type of intermolecular force where one dipole interacts with another molecule, inducing a dipole in it.