Electrons and Bonding

Created by

Harris

Cards (49)

How many electrons are in the first 4 shells?
1 - 2 electrons
2 - 8 electrons
3 - 18 electrons
4 - 32 electrons
What are atomic orbitals?
a region around the nucleus that can hold up to two electrons with opposite spins
What is the shape of s- orbitals - draw the graph
electron cloud is in shape of a sphere
How many orbitals and so electrons are in s-, p- and d-sub-shells?
s - 1 orbital, 2 electrons
p - 3 orbitals, 6 electrons
d - 5 orbitals, 10 electrons
What is the shape of p orbitals?
dumb-bell shaped electron cloud
3 separate p orbitals at right angles to each other
How are the orbitals with the same energy filled?
one in each orbital before pairing
How are shorthand electron configurations written?
use previous noble gas in format [noble gas] and all sub-shells in it are accounted for
How is the periodic table divided into blocks?
s block - group 1 and 2
p block - group 3 to 8
d block - centre - between group 2 and 3
What is ionic bonding?
the electrostatic attraction between positive and negative ions
What is the structure of ionic compounds?
giant ionic lattice
Describe and explain the melting and boiling points of ionic compounds
High melting and boiling points
A lot of energy required to break strong ionic bonds - strong forces of electrostatic attraction between ions
The melting points are higher for lattices with greater ionic charges - stronger attraction between ions
Describe and explain the solubility of ionic compounds
Dissolve in polar solvents e.g water
Polar water molecules break down the lattice and surround each ion in solution
greater ionic charge means there is stronger electrostatic attraction between ions so less soluble
Describe and explain the electrical conductivity of ionic compounds
Does not conduct when solid
Ions in fixed position so no mobile charge carriers
Does conduct when aqueous or molten (liquid)
solid ionic lattice breaks down so ions free to move as mobile charge carriers
What are the properties of ionic compounds?
high melting and boiling points
dissolve in polar solvents
conduct electricity when aqueous or liquid
What is covalent bonding?
the strong electrostatic attraction between a shared pair of electrons and oppositely charged nuclei
What happens to orbitals in covalent bonding?
orbitals overlap
What is a dative covalent bond?
shared pair has been supplied by only one bonding atom
e.g formation NH4 from NH3 + H+
represented by arrowhead
What is average bond enthalpy?
measurement for covalent bond strength larger value = stronger bond
What is electron repulsion theory?
electron pair repel so arranged far apart as possible
this minimises repulsion so holds bonded atoms in definite shape
How do lone pairs effect bonded pairs?
stronger repulsion so repel bonded pairs closer together
for each lone pair bond angle reduced by 2.5 degrees
What is a tetrahedral shape?
bonded pairs - 4 pairs
lone pairs - 0 pairs
bond angle - 109.5 degrees
shape -
What is a pyramidal shape?
bonded pairs - 3 pairs
lone pairs - 1 pairs
bond angle - 107 degrees
shape -
What is a non-linear shape?
bonded pairs - 2 pairs
lone pairs - 2 pairs
bond angle - 104.5 degrees
shape -
What is a linear shape?
bonded pairs - 4 pairs 2 regions
lone pairs - 0 pairs
bond angle - 180 degrees
shape -
What is a trigonal planar shape?
bonded pairs - 3 pairs
lone pairs - 0 pairs
bond angle - 120 degrees
shape -
What is a octahedral shape?
bonded pairs - 6 pairs
lone pairs - 0 pairs
bond angle - 90 degrees
shape -
What is electronegativity?
the attraction of a bonded atom for the pair of electrons in a covalent bond
What factors effect electronegativity?
increases across and up the periodic table
nuclear charge increases - nucleus has greater charge and so force of electrostatic attraction to valence electrons
atomic radius decreases - nucleus stronger force of electrostatic attraction to valence electrons as closer
How can you deduce what bond based on electronegativity difference?
covalent - 0
polar covalent - 0 - 1.8
ionic - greater than 1.8
What is a non-polar bond?
bonded electron pair is shared equally between atoms
How do you know when a bond is non-polar?
when bonded atoms are the same
bonded atoms have the same or similar electronegativity
What is a polar bond?
the bonded electron pair is shared unequally between bonded atoms
How do you know when a bond is polar?
when bonded atoms are different and have different electronegativity values
What is a dipole?
pair of opposite charges separated
What type of dipole do polar covalent bonds have?
permanent dipole
What are intermolecular forces?
weak interactions between dipoles of different molecules
What are the types and relative strengths of intermolecular forces?
induced dipole-dipole interactions - London forces (weakest)
permanent dipole-dipole interactions (stronger)
hydrogen bonding (strongest)
How are dipoles induced (London forces)?
instantaneous dipole forms in molecule - more electrons at one side of molecule causes this
more electrons in side molecule repel those in molecule next to it so they move to one side - inducing a dipole
induced dipole further induces dipoles on neighbouring molecules
they then attract one another
temporary
What factors effect London forces?
more electrons = stronger London forces
larger instantaneous and induced dipoles
greater induced dipole-dipole interactions
stronger attractive forces between molecules
more energy needed to overcome stronger force
When are permanent dipole-dipole interactions present?
between polar molecules