Shapes of Molecules, Ions Bond Polarity, structure & Intermolecular Forces Flashcards
Why does a lone pair of electrons repel more than a bonded pair?
The lone electron is slightly closer to the central atom which contains the positive protons and it also occupies more bonding space so it repels more strongly
What is the bond angle of a tetrahedral molecule? Example?
109.5
CH4
What is the bond angle of a pyramidal molecule? Example
107
NH3
What is the bond angle of a non-linear molecule? Example
104.5
H20
What is the bond angle of a linear molecule? Example?
180
O2
What is the bond angle of a trigonal planar molecule?
120
What is the bond angle of a tetrahedral molecule?
109.5
What is the bond angle of a octahedral molecule?
90
What is are the main rules in electron repulsion theory?
Electrons repel each other and are arranged to minimise repulsion as much as possible
The electron repulsion is definite in terms of positioning so the shape of the electron is determined by this
Why are molecules are non-polar?
They either:
Are the same atoms bonded together
Or
The two atoms have the same/similar electronegativity
When drawing charges on molecules, usually, what charge is hydrogen?
Positive
How can you determine which atom is positive and which negative in a polar molecule?
The atom with the largest electronegativity has the negative charge
What is electronegativity?
The ability of an atom to attract a pair of electrons to itself
Which elements are classed as being very electronegative?
Fluorine, nitrogen, oxygen
Which type of intermolecular forces are temporary?
Van Der Waals
What is the difference between a polar and non-polar covalent bond? What causes this?
Non-polar covalent bonds equally share a pair of electrons whereas polar covalent bonds unequally share electrons due to differences in electronegativity
When does a dipole-dipole force occur?
When a partial charge from within a molecule has uneven distributions of electrons which is permanent
What are the properties of simple molecular structures?
Weak intermolecular forces
No delocalised electrons
Why can’t ice conduct electricity?
It’s H+ ions don’t travel around quick enough
Why is ice strong?
H+ and O- ions form strong intermolecular forces
Give the properties of a giant covalent structure like diamond?
Strong covalent bonds High melting and boiling point Lots of energy required to change state Giant lattice structure No delocalised electrons
Which structure does graphite have? Can it conduct electricity?
Giant covalent
Yes, because it has delocalised electrons
Which two structures contain no delocalised electrons?
Simple molecular
Giant covalent
Why does a metallic structure have a high strength?
Attraction between delocalised electrons and ions causes high strength which require a lot of energy to be broken
