Elements of Life - Molecular Structure Flashcards
What is the bond angle for tetrahedral molecules?
109.5
Why is H2O a bent molecule?
It has 2 bonding and 2 non-bonding pairs of electrons.
They all repel to be as far apart as possible, but the non-bonding pairs repel stronger, therefore we get a bent shape with a 104.5 angle
What is the bond angle of a trignal planar molecule?
120
What is the bond angle of a linear molecule?
180
What is the bond angle of an octahedral molecule?
90
What are the bond angles for trignal bipyriamidal molecules?
90 and 120
What is the rule for calculating bond angles when a molecule has lone pairs of electrons?
reduced by 2.5 for every lone pair
If a molecule has 6 paired electrons what shape will it assume?
octahedral
If a molecule has 5 electron bonding pairs, what shape is it?
trignal bipyramidal
Which equation links moles, mass and relative atomic mass?
Moles = mass / molar mass
Define an emperical formula
the ratio of atoms is a compound
eg C2H6 would have be empirical formula of CH3
Define a molecular formula
The actual number of atoms in a molecule
eg C2H5OH would have the molecular formula of C2H6O
What is the general formula for percentage bymass?
atomic mass of elements in compound / atomic mass of compound
x 100
Define water of crystallisation
When H2O molecules are present inside crystals but not bonded within the structure
Define electronegativity
The tendency of an element to attract electrons in covalent bonds
What determines whether a bond is ionic or covalent?
The differences of electronegativity between the elements
big difference -> ionic -> one can pull electrons a lot stronger
medium -> polar covalent
small -> covalent
Which elements does aluminum only form ionic bonds with?
F and O
Which group of elements will never form a covalent bond and why?
Group 1
they are too far apart from other elements
List the properties of ionic compounds
- > all solids at room temperature
- > high melting and boiling points
- > form giant ionic lattices
- > conduct electricity when liquid or aqueous
- > SOME dissolve in water but not all
List the insoluble ionic compounds
- > barium, lead, calcium and silver sulphates
- > silver and lead halides
- > metal carbonates
- > metal hydroxides (excluding group 1 and ammonium)
Define a dative covalent bond
When both bonding electron originate from the same atom
What is the solubility of nitrate ions?
Always soluble in water
