Unit 1(c) - Structure And Bonding Flashcards
What is a pure covalent bond?
In a pure covalent bond, electrons are equally shared
When do molecules have pure covalent bonding?
Atoms have the same electronegativity, for example diatomic elements
What is a polar covalent bond?
A polar covalent bond has an unequal sharing of electrons
When do molecules have polar covalent bonds?
Difference in electronegativity creates a permanent dipole as electrons are pulled closer to one atom
What is an ionic bond?
An ionic bond is the electrostatic between the positive ions of one element and the negative ions of another element
What is electronegativity?
Electronegativity is a measure of the tendency of an atom to attract a binding pair of electrons
Which bonds have no ionic character?
Bonds between atoms of the same elements
What is an isoeletric substance?
A substance where both ions have the same electron arrangement (nearest noble gas)
What structures do ionic compounds have?
3 dimensional lattices
What is the overall charge of an ionic compound?
Zero
Do ionic compounds conduct electricity?
Only when molten or in solution, solid ionic compounds do not conduct electricity as the lattice holds the ions in place
What are intermolecular forces?
The forces of attraction which hold molecules together
What are the three main types of intermolecular forces?
- London dispersion forces
- Permanent dipole - Permanent dipole attraction
- Hydrogen bonding
Discuss London Dispersion Forces
- Occur between atoms (noble gases) and molecules
- Only force between non polar molecules and monatomic elements
- Weakest intermolecular force
Discuss PD-PD attraction
- Occur between polar molecules
- Stronger than LDF
- Some molecules can have an overall polarity because of a PD
What is a polar molecule?
A molecule which has a slightly positive side and a slightly negative side
Why are some individual covalent bonds polar, but the molecule is not polar?
If the molecule is symmetrical it will be non polar - the dipoles cancel each other out
What property effects the overall polarity of a molecule?
The shape of the molecule - symmetrical molecules are non polar
What is hydrogen bonding?
Hydrogen bonding occurs in molecules which have a strong covalent bond between a hydrogen atom and a highly electronegative element (N, O or F)
What determines whether a substance will dissolve in a solvent?
Intermolecular forces
What rule can be applied to solvents?
Like dissolves like - polar substances will dissolve in polar solvents and vice versa
