2.2 electrons, bonding and structure Flashcards
what is ionic bonding
the electrostatic force of attraction between positive and negative ions
what are giant ionic lattices?
three dimensional structure of oppositely charged ions, bonded together by strong ionic bonds acting in all directions.
all ioinc compounds are GIANT IONIC LATTICES
describe the MP/BP of ionic compounds
high vs most covalent substances
-almost ALL ionic compounds are solid at room temp
explain the MP/BP of ionic compounds?
High MP/BP
- high temps are required to provide the large quantities of energy needed to overcome the strong electrostatic forces of attraction between oppositely charged ions
suggest a reason for the difference in BP of NaI, NaBr, and NaCl?
chloride ions are smaller than Bromide ions and much smaller than iodide ions, allowing them to be held together closer in their ionic lattice structure, strengthening the forces of attraction between the oppositley charged ions in NaCl vs NaBr and NaI, so more energy is required to overcome the bonds
why does KBr have a lower BP than NaBr
-sodium ions are smaller than potassium ions so can pack more closely together in their giant ionic lattice tsructure.
-increases strength EfAs between oppositely charged ions
-more energy to overcome
describe and explain the solubility of many ionic compounds?
-dissolve in polar substances [water]
-polar water molecues are attracted to ions on the surface of the lattice
-water molecules bond to the ions, weakening the ionic bonding
-ionic bonds are broken
-ions become surrounded by water molecules and break free from the lattice
why may an ionic compound not be considered very soluble?
-in compounds made of ions w large charges
- ionic bonds may be too strong for water molecules to break down the lattice structure
- compound is therfore insoluble in water
what must take place in order for an ionic compound to dissolve in water?
what does solubility on an ionic compound depend on?
-Water molecules MUST attract and surround the ions
-ionic lattivce MUST be broken down
-relative strength of attractions within giant ionic lattice
-attraction between ions and water molecules
what must take place in order for an ionic compound to dissolve in water?
what does solubility on an ionic compound depend on?
-Water molecules MUST attract and surround the ions
-ionic lattice MUST be broken down
-relative strength of attractions within giant ionic lattice
-attraction between ions and water molecules
describe the electrical conductivity of ionic compounds?
-solid state > do not conduct (insulators)
- molten (liquid state) or aqueous (disssolved in water) > electrical conductors
explain the electrical conductivity of ionic compounds?
solid
-ions held in fixed position in lattice
-there are no mobile charge carriers
-so cannot conduct electrical energy
molten/aqueous
-solid ionic lattice breaks down
-ions now free to move as mobile charge carriers
-can conduct electrical energy
how is electrical conductivity typically effected by concentration?
typically increases, bc more charge-carriers (free-ions) to carry current through the water
why would the same conc solution of CaCl2 conduct better than NaCl?
more dissolved ions in the Calcium Chloride solution which are able to carry a charge
why would the same conc solution of CaCl2 conduct better than NaCl?
more dissolved ions in the Calcium Chloride solution which are able to carry a charge
describe and explain the malleabilty of ionic compounds?
brittle
disruption of the arrangement of (+) and (-) ions is almost guaranteed to end up with repulsions between similarly charged ions that end up next to each other
what is a covalent bond?
the strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms
which elements form ‘multiple’ covaleent bonds?
oxygen- double
nitrogen- treble
*what is a dative covalent bond
covalent bond (EfA between shared pair e-s and nucluei of bonded atoms) in which shared pair electrons are supplied by one of the bonding atoms only
-show as 2 dots/2 crosses
example of dative covalent bond formations?
ammonia (NH3) and hydrogen (H+) ion
H+ ion has no electrons
NH3 has 1 lone pair on Nitrogen atom
(draw as two dots/crosses-same as using for N) and (an arrow from N to H to show that they bothe come from N)
how many electrons can fill the first 4 shells?
1, 2
2, 8
3, 18
4, 32
define the term atomic orbital
region around the nucleus that can hold up to two electrons with opposite spins
define the term shell
a number of orbitals with the same principal quantum number(n)
define the term electron
cloud of negative charge
-negative charge cloud takes shape of orbital it occupies
define the term sub shell
orbitals of the same type in the same shell
how many electrons can the 3d orbital hold?
2
ORBITALS CAN HOLD MAX ELECTRONS
how many electrons can the s sub shell hold
2
how many electrons can a p sub shell hold
(3x2) 6
how many electrons can a d sub shell hold?
(5x2) 10
how many electrons can the f sub sell hold?
97x2) 14
what shape is the s sub shell
sphere
-draw circle
what shape is the p sub shell?
dumbell
-draw figure of 8
what order do shells fill in?
shells fill in order of increasing energy
rules for filling orbitals?
1.orbitals w lowest energy fill first
2. up to 2 electrons per orbitals but MUST have opposite spins
3. If have orbitals w same energy, put electrons into individual orbitals before pairing them (electrons in sam eorbital repel)
state the subshells in order of increasing energy up to 4f
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 4d, 4f
4s is LOWER energy> 3d so fills first
2 exceptions for electron orbital filling
chromium and copper:
Cr: expected: 3d^4 4s^2 Actual: 3d^5 4s^1
Cu: expected: 3d^9 4s^2 Actual: 3d^10 4s^1
In both cases 4s subshell only contains 1 electron even though there are electrons in the 3d subshell, this is because the 3d subshell is more stable when either half full (Cr) or full (Cu)
define electronegativity
ability of an atom to attract the pair of electrons in a covalent bond
define non-polar bond
bonded electron pair shared equally between the nuclei of the bonded atoms
when do non-polar bonds occur?
small diff in electronegativity
-bonded polar atoms are the same (H2, Cl2)
-bonded atoms have same/similar electronegativities (C and H)
what is a pure covalent bond?
non-polar bond, no/negligible diff in electronegaticity, electron pair shared equally between nuclei of bonded atoms
what is a polar bond?
bonded pair of electrons is shared unequally between bonded atoms
-each atom will have a small partial +/- charge
form “polar covalent bonds”
define the term dipole
the seperation of opposite (partial) charges
which shapes are symetrical?
linear
trigonal planar
tetrahedral
octahedral
