1.3 bonding Flashcards
Name 5 compound ions
Ammonium NH4+
Nitrate NO3-
Carbonate CO3^2-
Sulfate SO4^2-
Hydroxide OH-
What is an ionic bond?
Many strong electrostatic forces of attraction between positive and negative ions
Examples of ionic compounds (atoms held in lattice)
MgO, MgCl2, NaCl
Why can ionic compounds conduct electricity when molten/ dissolved?
Ions are free to move through the structure and carry a charge
Do ionic compounds have a high or low mp? Why?
Many string electrostatic forces between opposite charges take lots of energy to break
Why are ionic compounds soluble?
Water molecules are polar so pull ions away from lattice causing it to dissolve
Why are ionic compounds brittle?
Layers slide causing like charges to line up and repel
What is a molecule and how are they held together
Examples
Two or more atoms bonded and held together by string covalent bonds
Cl2, H2O, CO, C2H5OH
What is a covalent bond?
A shared pair of valence electrons between the nuclei of 2 atoms
Do simple covalent compounds have a high or low mp? Why?
Weak intermolecular forces
What is graphite?
Carbon atoms arranged in sheets of flat hexagons covalent it bonded with 3 bonds.
Properties of graphite
1) slippery as weak vanderwaals between layers
2) electric conductor as 4th electron is delocalised
3) strong and light as layers far apart so low density
4) High mp as strong covalent bonds
5) insoluble in any solvent as strong covalent bonds
What is diamond?
Each carbon atom bonded covalently to 4 others forming tetrahedral shape and crystal lattice structure
Properties of diamond
1) high mp as strong covalent bonds
2) extremely hard as strong covalent bonds
3) good thermal conductor as strong bonds so vibrations travel easily through stiff structure
4)can’t conduct electricity as all electrons bonded
5) insoluble in any solvent as strong covalent bonds
What is a coordinate covalent bond?
Examples?
An atom donates a lone pair of valence electrons to form a coordinate bond with another atom/ ion
Eg ammonium ion and hydroxonium ion
What is a charge cloud?
Where you have a big chance of finding an electron
Shape of charge cloud affects how much it repels other charge clouds. Order the repulsion
Lone pair to lone pair Strong
Lone pair to bonded pair. Middle
Bonded pair to bonded pair Weak
How do you represent different directions in shapes of molecules?
/\ towards
——— away
_________ parallel to paper
What is electronegativity?
The ability of an atom to attract the bonding electrons in a covalent bond.
What does electronegativity depend on?
1) atomic radius
2) e- shielding
3) charge
What happens to electronegativity down a group?
Decreases
Increase radius so more energy levels so more shielding and less nuclear attraction.
What happens to electronegativity across a period?
Increases
Decrease radius as higher nuclear charge there is no extra e- shielding so nuclear attraction increases
What is a non polar bond?
Equal electronegativity so electrons are equally attracted to both nuclei eg in diatomic gases
What is a polar bond?
Atoms with different electronegativity- bonding electrons pulled towards more electronegative atoms. Bigger difference, more polar
What is a dipole?
A difference in electronegativity causing an uneven charge distribution
If the bonds are symmetrical, is it a permanent dipole?
No they cancel
If bonds are in same rough direction, is it permanent dipole?
Yes bonds don’t cancel so charge unevenly distributed
What is an intermolecular force?
Forces between molecules
What are van der waals forces?
Electrons move quickly in charge cloud creating temporary dipole. This causes opposite dipole in other direction on neighbouring atom etc so they are attracted
Why do larger molecules have higher mp and bp?
Bigger radius so more electrons so more van der waals more energy needed to overcome
What are permanent dipole dipole forces?
Polar molecules attracting other polar molecules. There will be weak electrostatic forces of attraction between d+ and d-
What is hydrogen bonding?
Bonding between H and and F,O or N atom with a lone pair
Why does water have higher bp than other group 6 hydrides?
Extra energy needed to break hydrogen bonds in water
Why is ice less dense than water?
When it cools, molecules make more hydrogen bonds and arrange in regular lattice. H bonds are long so big distance between molecules
What is metallic bonding?
Many strong electrostatic forces of attraction between delocalised valence electrons and layers of positive metal ions.
Why do metals have high melting points?
Strong electrostatic forces of attraction. The more delocalised electrons the stringer the bonds and the higher the mp
Why are metals ductile and malleable?
No bonds holding specific ions together so layers can slide
Why can metals conduct electricity?
Delocalised electrons are free to move throughout the structure and carry a charge
Why can metals conduct heat?
Delocalised electrons can pass kinetic energy to each other
Why aren’t metals soluble?
The metallic bond is too strong
What are giant covalent structures?
A type of crystal structure with a huge network of atoms bonded covalently
