Chapter 3 - bonding Flashcards
State what a covalent bond is
Strong bond involving a shared paired of electrons
State what an ionic bond is
The electrostatic forces of attraction between oppositely charge ions caused by electron transfer
State what a metallic bond is
The strong electrostatic forces of attraction between the giant lattice of positive ions and the mobile sea of delocalised valence shell electrons
Sate what a hydrogen bond is
(the strongest of the weak forces of attraction) the electrostatic forces of attraction between delta+ hydrogen of 1 molecule and delta- of another (NOF group)
State what a dative covalent bond is
The strong bond formed when a lone pair of electrons is donated to an electron deficient species, once formed it behaves as a covalent bond
State what a permanent dipole dipole force is
The weak electrostatic force of attraction between delta+ and delta- regions of polar molecules
State what a van der Waals force is
(The weakest of the weak) very weak electrostatic forces of attraction between all molecules at all times, due to the changing position of the electron cloud, inducing temporary dipoles in adjacent molecules
Define what is meant by the term electronegativity
For an associated covalent bond, the tendency for an atom to attract negative charge/electrons towards itself
What can increase a van der Waals force?
The size of the molecule (larger), therefore the number of electrons
When drawing a hydrogen bond/hydrogen attraction what 3 things must you include?
All lone pairs of electrons, delta+/-, hydrogen dotted to a lone pair of electrons
Why does electronegativity decrease down a group?
There’s more inner electron shell shielding
What 3 things does electronegativity depend upon?
Nuclear charge, distance between the nucleus and the outer shell electrons, inner electron shell shielding
Why does electronegativity increase across a period?
There’s a greater nuclear charge pulling on the same outer shell of electrons; the atom becomes smaller
When is a covalent bond polar?
When the difference in electronegativity is about 1
When is a covalent bond pure?
When there is a very little/ no difference in electronegativity
When is an ionic bond pure?
When there is a large difference in electronegativity >2.5
When does an ionic bond have covalent character?
When there is a difference in electronegativity about 2
What does the valence shell electron pair repulsion theory state?
Electron pairs repel each other as far apart as possible to minimise repulsion, lone pairs repel more
Lone pairs decrease the bond angle by how much?
2.5 degrees
Name the shape of the molecule when 2 atoms have equal repulsion and bond angle
linear, 180
Name the shape of the molecule when 3 atoms have equal repulsion and the bond angle
trigonal planar, 120
Name the shape of the molecule when there 4 atoms repelling equally and the bond angle
tetrahedral, 109.5
Name the shape of the molecule when there are 3 atoms and 1 lone pair repelling and the bond angles
trigonal pyramidal 107
Name the shape of the molecule when 5 atoms have equal repulsion and include the angles between the bonds
trigonal bipyramidal, 90 and 120
