2.2 electrons, bonding and structure Flashcards
define an orbital
spaces in an atom where electrons are found in an opposite spin pair
what is the shape of an s orbital?
spherical
what is the shape of a p orbital?
dumbbell shape
how many electrons can the s subshell hold?
2 electrons of opposite spins (one box/orbital)
how many electrons can the p subshell hold?
6 electrons paired up with opposite spins (3 boxes/orbitals)
how many electrons can the d subshell hold?
10 electrons paired up with opposite spins (5 boxes/orbitals)
how many electrons can the f subshell hold?
14 electrons paired up with opposite spins (7 boxes/orbitals)
name the 3 rules of orbitals
- electrons fill up from the lowest available energy level
- two electrons of opposite spins in each orbital (box)
- when an energy level is not full, the electrons occupying it will try to remain unpaired
name 2 transition metals that do not follow the box notation pattern and explain why this occurs
chromium - has a 4s1 then 3d5 - instead of having 4s2 then 3d4, electron from the 4s orbital moves to the 3d one so they are both partially full which is more stable.
copper - has 4s1 and 3d10 - having a partially full 4s orbital and a full 3d orbital is more stable than having a fun 4s one and an almost full 3d one.
which energy level fills up first, 4s or 3d?
4s - because 4s is lower in energy than 3d so it fills up first.
what is the rule for forming transition metal ions?
ONLY for transition metals - when forming ions, the electrons in the 4s orbital are removed FIRST.
define the term ionic bond
the electrostatic force of attraction between oppositely charged ions
what kind of structures to ionic compounds form?
giant ionic lattice structures
name and describe 4 properties of ionic compounds
- high melting/boiling point - strong electrostatic forces require a lot of energy to be broken
- weak strength/brittle - moving layers of ions brings the same charged ions into close contact causing repulsion, and the forces being weakened, causing the lattice to break.
- only conduct electricity in a liquid/aqueous form - when molten or dissolved, ions can move and carry charge.
- soluble in water - water is polar, and so it attracts the ions away from each other, causing the lattice to break away.
define covalent bonding
bonds formed between non-metals in which they share pairs of electrons in order to achieve a full outer shell.
the bond is created by a strong electrostatic attraction between the shared pair of valence electrons and the positive nuclei.
name and describe 3 properties of simple covalent molecules
- low melting/boiling point - weak intermolecular forces require little energy to be broken
- do not conduct electricity - no mobile electrons to carry charge
- strong covalent bonds - shared pair of electrons and strong electrostatic force hold atoms together
what kind of structure to giant covalent compounds form?
lattice structures
name 4 giant covalent compounds
diamond
graphite
silicon dioxide
graphene
what is dative covalent (coordinate) bonding?
when one element provides a full pair of electrons so one shared pair comes from one atom.
e.g. ammonium ion (NH4+)
name 5 properties of diamond
- high melting and boiling point - strong covalent bonds
- very hard - strong covalent bonds and lattice structure create a dense overall structure
- thermal conductor - vibrations travel through easily because of denseness and strong bonds
- doesn’t conduct electricity - no mobile electrons - fixed into the lattice bonding
- won’t dissolve in any solvent
name 5 properties of graphite
- lubricant material - layers slide over each other easily due to weak intermolecular forces.
- conducts electrons - delocalised 4th electron per carbon can move and carry charge
- not dense - layers far apart (good for light weight but strong sports equipment)
- high melting/boiling points - strong covalent bonds
- insoluble in any solvent - strong covalent bonds won’t break down
what is average bond enthalpy?
the average amount of energy required to break a particular bond
what is the order of repulsion between lone and bonded pairs of electrons? (most - least)
2 lone pairs have the most repulsion
then lone and bonded pairs
then 2 bonded pairs have the least repulsion
what shape would a molecule with 2 bonded electron pairs have? what angle would they have?
linear molecules
180 degrees
what shape would a molecule with 3 bonded electron pairs have? what angle would they have?
trigonal planar
120 degrees
what shape would a molecule with 4 bonded electron pairs have? what angle would they have?
tetrahedral
109.5 degrees
what shape would a molecule with 3 bonded electron pairs and one lone pair have? what angle would they have?
(trigonal) pyramidal
107 degrees
what shape would a molecule with 2 bonded electron pairs and 2 lone pairs have? what angle would they have?
non-linear/bent
104.5 degrees
what shape would a molecule with 5 bonded electron pairs have? what angle would they have?
trigonal bipyramidal
120 and 90 degrees
what shape would a molecule with 6 bonded electron pairs have? what angle would they have?
octahedral
90 degrees
define electronegativity
the ability of an atom to attract the bonding electron pairs in a covalent bond
na6me 2 trends of electronegativity in the periodic table
increases from left to right (towards halogens)
increases from bottom to top (towards smaller atoms)
define polar bond
a bond in which the electrons are unevenly distributed (or there is a permanent dipole) due to a difference in electronegativity
define polar molecule
a molecule where there is a net/overall dipole moment, causing a partially negative area (ẟ⁻) and a partially positive area (ẟ⁺) / polar molecules arranged asymmetrically
define a dipole
a difference in polarity
define inTERmolecular force
an attraction between molecules
define inTRAmolecular force
an attraction between atoms, holding them together usually
name the three intermolecular forces. whats their order of strength?
induced dipole-dipole - weakest
permanent dipole-dipole - middle strongest
hydrogen bonds - strongest
whats an induced dipole-dipole intermolecular force?
instantaneous intermolecular bond between moving electrons.
what happens to strength of intermolecular forces and melting and boiling points as atom size increases? why?
as atom size increases, the intermolecular force strength increases.
this is because as atom size increases, electron number increases meaning more electron will cause a larger partial charge and therefore a stronger induced dipole-dipole interactions. stronger interactions require more energy to be broken = higher melting + boiling point.
whats a permanent dipole-dipole intermolecular force?
constant force between polar molecules
what is a hydrogen bond?
an intermolecular force occurring between hydrogen atom and another atom with a large difference in electronegativity. the hydrogen bonds to a lone pair of electrons.
which atoms does hydrogen bond to in a hydrogen bond? why?
oxygen, nitrogen and fluorine.
because the dipole is so strong because of the difference in electronegativity.
name 5 unusual properties of water
higher mp and bp than usual ice is less dense than water high surface tension higher viscosity cohesion
why does water have a higher mp and bp ?
hydrogen bonds are stronger than other intermolecular bonds because they can stretch over a long distance so need more energy to be overcome.
why is ice less dense than liquid water?
the structure of ice is a regular lattice. the long hydrogen bonds hold the molecules far apart creating a larger volume with the same mass of water.
what is viscosity?
how thick a liquid is
why does water have a higher viscosity than other like structures?
the strong hydrogen bonds create a resistance to flow
why does water have high surface tension?
the water molecules at the surface of the water are bonded to the molecules below them. these hydrogen bonds below hold up the surface molecules.
what is cohesion?
attraction between molecules of the same substance
why does water have cohesion?
each water molecule could have up to 4 hydrogen bonds, causing greater attraction and greater cohesion.
