Bonding and Structure Flashcards
definition of a covalent bond
the electrostatic attraction between two nuclei and a shared pair of electrons
definition of ionic bond
the electrostatic attraction between two ions of opposite charge
definition of metallic bond
the electrostatic attraction between positivey charged metal ions and delocalised electrons
what is an ion
a charged particle that has either lost of gained electrons, resulting in a charge and a stable electronic structure
what is electrostatic attraction
attraction between positively charged and negatively charged particles
what is an ionic lattice
the arrangement of ions into a large structure, consisting of alternating positive ions and negative ions
what are delocalised electrons
electrons that are not tied to a particular atom, but are free to move throughout the structure
what is a metallic lattice
a giant, regular, repeating structure of positive metal ions existing in a sea of delocalised electrons
what is a crystal structure
a substance which has a type of structure
what is a dative bond / co ordinate bond
a covalent bond where the shared electron pair comes from only one participating atom
what is a lone pair
a pair of electrons on an atoms outer shell that is not being used in a bond
what is electronegativity
the tendency of an element to attract a shared pair of electrons to itself within a covalent bond
what is a polar bond
a bond formed between atoms with differing electronegativities
what is a permanent dipole
occurs in a molecule which is asymmetric and has one side which is more positive and one which is more negative
what are pd-pd interactions
interactions that occur between molecules that have permanent dipoles
what are london forces
instantaneous dipole induced dipole forces arising from random movement of electrons
how do london forces arise
- random movement of electrons
- more electrons = greater london forces
how do pd-pd forces arise
differences in electronegativities between atoms in a molecule
causes an asymmetrical charge across a molecule
how do hydrogen bonds arise
when hydrogen is directly bonded to N, O or F
what is the weakest IMF
london forces
what is the strongest IMF
hydrogen bonds
what are hydrogen bonds
molecules that contain hydrogen atoms directly bonded to N O or F atom will form these bonds with other molecules that contains H directly bonded to N O or F
what are isoelectronic species
species with the same electronic figure
what is the name and bond angle of a molecule with 2 bonding pairs, no lone pairs
linear, 180
what is the name and bond angle of a molecule with 3 bonding pairs, no lone pairs
trigonal planar, 120
what is the name and bond angle of a molecule with 2 bonding pairs, 1 lone pair
bent/ V shaped, 117.5
what is the name and bond angle of a molecule with 4 bonding pairs, no lone pairs
tetrahedral, 109.5
what is the name and bond angle of a molecule with 3 bonding pairs, 1 lone pair
trigonal pyramidal, 107
what is the name and bond angle of a molecule with 2 bonding pairs, 2 lone pairs
bent/ v shaped, 104.5
what is the name and bond angle of a molecule with 5 bonding pairs, no lone pairs
trigonal bipyramidal, 120 & 90
what is the name and bond angle of a molecule with 3 bonding pairs, 2 lone pairs
T shaped, 175, 85
what is the name and bond angle of a molecule with 4 bonding pairs, 1 lone pair
see-saw, 117.5 equatorial & 87.5 axial
what is the name and bond angle of a molecule with 6 bonding pairs, no lone pairs
octahedral, 90
what is the name and bond angle of a molecule with 5 bonding pairs, 1 lone pair
square pyramidal, 90 equatorial & 87.5 axial
what is the name and bond angle of a molecule with 4 bonding pairs, 2 lone pairs
square planar, 180 & 90
what’s the general structure of an answer when explaining why a molecule has that bond shape and that bond angle
there are _ electron pairs around the central atom: _ bonding pairs and _ lone pairs
All electron pairs spread out as far as possible to minimise repulsion
Lone pairs repel more than bonding pairs
So the shape is _ and the angle is _
state what affects the strength of london forces
number of electrons in a molecule
more electrons = greater london forces
explain why CF4 is not a polar molecule, despite the C-F bond being polar
Draw a diagram clearly showing the shape of CF4 as part of your answer
CF4 is tetrahedral and the bond polarities are symmertrical
So the bond polarities cancel
why must hydrogen be bonded directly to N, O or F to form hydrogen bonds? what is special about these atoms?
They have the highest electronegativities
They have low shielding / small atomic radius
For relatively high nuclear charge
explain why some ionic compounds may be insoluble in water
The energy released when water forms attractions to the ions is not enough energy to break the electrostatic attractions within the lattice
Pentane, C5H12, is fully miscible with octane, C8H18. Explain why by considering the types of intermolecular forces present in both compounds in your answer
the only IMF present in both are London Forces
So the strength of forces between pentane and octane are similar to the strength of forces in each separate substance
