Module 2: Section 2 Flashcards
How many electrons can the following sub-shells hold;
- S sub-shell
- P Sub-shell
- D Sub-shell
- F sub-shell
S Sub-shell = 2 electrons
P Sub-shell = 6
D Sub-shell = 10
F Sub-shell = 14
What shapes are S orbitals and P orbitals?
S orbitals are spherical.
P orbitals are dumbbell shaped.
When does ionic bonding occur?
Occurs between a metal & non-metal.
Define ionic bond.
Ionic bond = electrostatic attraction between 2 oppositely charged ions.
Describe a giant ionic lattice.
Made up of the same basic unit repeated over and over again.
Each ion is electrostatically attracted in all directions to ions of the opposite charge.
Strong ionic bonds means lots of energy is needed to break up the lattice.
Give 3 behavioural characteristics of ionic compounds.
- Conduct electricity when molten or dissolved, but not as a solid. As a liquid, the ions are mobile, but as a solid the ions are fixed in place by strong ionic bonds.
- Ionic compounds have high mpts and bpts.
Ionic lattices are held together by strong electrostatic forces, which require a lot of energy to be broken. - Ionic compounds tend to dissolve in water as water molecules are polar and are attracted to charged ions. They pull ions from the lattice and cause it to dissolve.
When does covalent bonding occur?
Occurs between 2 non-metals.
Define covalent bond.
Covalent bond = The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms.
Give an example of covalent bonding.
Cl2
How do you measure the energy required to break a covalent bond.
Average bond enthalpy measures the energy required to break a covalent bond.
What is dative covalent bonding?
Both electrons come from one atom.
Why do electron pairs repel eachother?
What time of electron pairs repel more?
Electrons are all negatively charged, so repel as much as possible.
Lone pairs repel more than bonding pairs.
Give the name and angle of a molecule with 2 electron pairs around the central atom.
180 degrees
linear molecules.
Give the name and angle of a molecule with 3 electron pairs around the central atom.
120 degrees
trigonal planar.
Give the name and angle of a molecule with 4 electron pairs around the central atom and no lone pairs.
109.5 degrees
tetrahedral
Give the name and angle of a molecule with 4 electron pairs around the central atom and 1 lone pair.
107 degrees
trigonal pyramidol
Give the name and angle of a molecule with 4 electron pairs around the central atom and 2 lone pairs
104.5 degrees
non-linear or bent
Give the name and angle of a molecule with 5 electron pairs around the central atom and no lone pairs.
90 degrees
trigonal bipyramidol
Give the name and angle of a molecule with 6 electron pairs around the central atom and no lone pairs.
90 degrees
Octrahedral
Define electronegativity.
Electronegativity = an atoms ability to attract the electron pair in the covalent bond.
What is the most electronegative element?
Fluorine.
What makes a bond polar.
In a covalent bond, the bonding electrons are pulled towards the more electronegative atom. This makes the bond polar.
What causes a permanent dipole-dipole.
In a polar bond, the difference in electronegativity between the 2 atoms causes a permanent dipol-dipole. Caused by a shift in electron density.
What intermolecular forces do polar bonds have?
Permanent dipole-dipole.
Shift in electron density occurs due to the difference in electronegativity.
Name the 3 types of intermolecular forces.
- Induced dipole-dipole/ London forces / dispersion forces
- Permanent dipole-dipole
- Hydrogen bonding.
What causes induced dipole-dipoles?
Electrons in charge clouds are always moving. At any moment electrons are to one side of the atom more than the other, creating a temporary dipole.
This dipole induces a dipole in neighbouring atoms, and so on, until a network of dipoles are created.
Dipoles are attracted to eachother as they are slightly charged.
Why do some molecules have stronger induced dipole-dipole forces?
- Large molecules have larger electron clouds, making the intermolecular forces stronger.
- Molecules with a large surface area have a bigger exposed electron cloud, making the intermolecular forces stronger.
When does hydrogen bonding occur?
Occurs when hydrogen is covalently bonded to fluorine, nitrogen or oxygen.
Give 2 unusual properties or ice
- Ice has an unusually high mpt due to hydrogen bonding.
2. Ice is less dense than water as it is held in a lattice shape by hydrogen bonds.
Why do simple covalent compounds have a low mpts and bpts?
Intermolecular forces are weak, so dont need much energy to overcome .
Why are polar molecules soluble in water?
Water is a polar molecules, so is attracted to charged ions in polar molecules, causing them to dissolve.
Why dont simple covalent compounds conduct electricity?
The compounds are uncharged and so do not conduct electricity.
Why dont simple covalent compounds conduct electricity?
The compounds are uncharged and so do not conduct electricity.
