Bonding Flashcards
What is ionic bonding?
bonding that usually occurs between a metal and a non-metal. Electrons are transferred, forming ions. These oppositely charged ions have strong forces of electrostatic attraction between them, forming a giant ionic lattice
What is covalent bonding?
. It involved pairs of electrons, that are shared between two atoms. These bonds form either simple molecular or giant covalent structures
What is a dative covalent bond?
A covalent bond when both the shared electrons are supplied from the same atom (e.g NH4+)
How do dative covalent bonds react?
exactly the same as covalent bonds
What is metallic bonding?
bonding that occurs in metals. Positive metals ions in a sea of delocalised electrons. Strong electrostatic attraction between positively charged metal ions and delocalised electrons. Forms a giant metallic lattice
How does the size of a metal ion impact the strength of the electrostatic forces present?
larger ions have weaker electrostatic forces of attraction, due to the increased distance between the positively charged nucleus and the delocalised electrons.
What are the 4 types of crystal structures?
ionic, metallic, macromolecular/giant covalent and simple molecular
Describe and explain the melting point of ionic structures
they have high melting and boiling points. This is due to strong electrostatic forces of attraction between oppositely charged ions.These require lots of energy to overcome.
Describe and explain the conductivity of ionic structures
they cannot conduct when solid but can when molten. This is because, when molten, the ions are able to move and carry charge
Why are ionic structures often brittle?
They are arranged in layers. If one layer moves, then it may cause like charges (on ions) to repel each other, and break apart the structure
Describe and explain the conductivity of metallic structures
They are often good conductors. The sea of delocalised electrons can carry charge and move throughout the structure
Why are metals often malleable?
as they are arranged in layers, which can slide over each other. There is no fragmentation as the delocalised electrons can move
Describe and explain the melting point of metallic structures
high melting and boiling points, due to strong electrostatic forces of attraction between positive metal ions and delocalised electrons, these require lots of energy to overcome
Describe and explain the melting point of simple molecular structures
low melting and boiling points, as the only inter-molecular forces present are weak Van Der Waals, these require little energy to overcome.
Describe and explain the conductivity of simple molecular structures
Do not conduct, as there are no charged particles present
Describe and explain the melting point of macro-molecular structures
very high boiling and melting points due to the giant lattice structure held together by very strong covalent bonds, that require lots of energy in order to overcome
Why can graphite conduct electricity?
As it is arranged in layers which have delocalised electrons, that can carry charge throughout the structure
What determines the shape of a molecule?
the electrons/bonding pairs that surround the central atom. they repel each other, causing the largest possible bond angle to occur
How does repulsion from a lone pair compare to repulsion from a bonding pair?
lone pairs repel more (covalent bonds reduced by approx. 2.5 deg. for each lone pair present)
What is the bond angle of a non-linear/bent molecule?
104.5 degrees
What is the bond angle of a trigonal planar molecule?
120 degrees
What is the bond angle of a triangular pyramid molecule?
107 degrees
What is the bond angle of a tetrahedral molecule?
109.5 degrees
What are the bond angles in a trigonal bi-pyramid molecule?
90 and 120 degrees
What is the bond angle in a octahedral molecule?
90 degrees
What is meant by the term ‘electronegativity’?
the tendency of an atom to attract the bonding pair of electrons in a covalent bond
What is a permanent dipole?
an uneven distribution of charge caused by a large difference in electronegativity
What is an induced dipole?
an uneven distribution of charge that occurs when the electrons are influenced by another charged particle
Why do Van Der Waals increase in strength with straight-chain molecules?
they are able to pack more closely together , reducing the distance over which the force acts, causing stronger attraction
What are hydrogen bonds?
bonds that form between either O, N or F and a Hydrogen molecule. They are the strongest intermolecular force
Draw KrF2
2 x f atoms, 3 x lone pairs
based on trigonal bipyramidal
Why is CBr4 not a polar molecule?
- it is tetrahedral/symmetrical
- so dipoles/charges cancel out
Why has CBr4 got a higher bpt. than CHBr3?
- CBr4 has Van Der Waals
- CHBr3 has dipole-dipole interactions and VDWs
- CBr4 has stronger VDWs as it has more electrons
