Pure Memory AS Module 2 Flashcards
Why do isotopes have the same chemical propertied? (2)
Isotopes of an element have the same number of protons and electrons but different number of neutrons, and are the same element
The chemical properties are determined by the electronic structure / electrons in the OUTER shell only, thus isotopes have the same chemical properties
Isoptopes definition
Same number of protons/ electrons, but different mass number due to having different number of neutrons
Relative isotopic mass?
Mass of an isotope relative to 1/12th the mass of an atom of CARBIN 12
Relative atomic mass (2)
WEIGHTED MEAN MASS OF AN ATOM OF AN ELEMENT
- relative to 1/12th the mass of an atom of carbon 12
What is water of crystallisation?
Many salts exist HYDRATED, so water molecules exist as part of their structure
When this is heated away, you get ANHYDROUS
2 assumptions made when doing water of crystallisation PAG
1) that all the water has been heated off
- can do this by getting consistent readings to constant mass
2) that no FURTHER DECOMPOSITION OF THE SALT HAS TAKEN PLACE, and thus less mass…
Base , salt , alkali definition
Base is a substance that can neutralise an acid
Salt is an acid whose h atoms replaced by metal
Alklai is a soluble base and dissociates to form OH - ions
Redox SPECIAL CASES?
H metal hydride
O in peroxides
O bonded to F
H = -1
O= -1
O = +2
Atomic orbital
A region around the nucleus that can hold up to two electrons of opposite spin
How is electrons organised
Shell
Sub shell
Specific orbitals
Each shell has quantum number
N =1 had one s sub shell. This has 1 s orbital
N=2 has 1 s sub shell and a p sub shell, s sub shell has 1 orbital and p has 3. P orbitals agsin 2 electrons
Etc
S sub shell and sub shell shape
S is sober, p is dumbbell
Periodic split into s , d , p blocks?
Based on the highest energy sub shell the electron configuration shows
Electorn pair repulsion theory 3 points
1 electron pairs around the central atom repel each other as far apart as possible
2) has this many pairs and lone pairs.3) lone pairs repel more than bonded pairs
Therefore
Sulfur dioxide specific shapes ( 2 double binds one lone pair )
Shape and angle?
Anomaly
Non linear shape but 120° angle
- because the double bonds have similar repulsion as the lone pair
So repulsion is even = 120° - but non linear shape just learn this one?
Electronegativity definition
The ability of an atom to attract the pair of electrons in a covalent bond
Why does electronegativity increase more right and up the periodic table you go
Hence which is most electro atoms
The ability to attract the electron pair comes from the nuclear charge . Going right the periodic table, the nuckear charge increases, but the nuclear radius also decreases, which increases nuclear attraction
- going down period increases charge but radius bigger (and shielding) so nuclear attraction defreasss
Therefore F O N most electronegative
How do induced dipole dipole interactions come about
3 points
1) movement of electrons in a molecule means at any instant, an INSTANTANEOUS DIPOLE WILL EXIST , but it’s position constantly changing
2) this INSTANEOUS dipole will induce a dipole on a neighbouring molecule, which will induce a dipole on its neighbour etc
3) the ATTRACTION between induced dipoles is called an induced dipole dipole interaction
A
How does number of electrons increase the London firce strength
And thus boilign pint
1) the larger the number of electrons in a molecule
2) the larger the INSTANEOUS dipole and thus induced dipole
3) so the stringer the attraction between induced dipoles/ stringer the induced dipole dipole interaction
Thus more energy needed to overcome these interactions and boiling point increases
Does everything have London forced
What doesn’t
GIANT COVALENT DOESNT
So like SIO2, watch out for group 4 to chekc
Solubility for simple molecular structure
Polar non polar mixes
Non polar and non polar (energy made enough )
Polar and polar is similar to polar and ionic, the polar substance attracts the polar molecular structure etc
Polar non polar no
Anomalous properties of water
2 main ones
1) higher density as a liquid then solid
- when becoming a liquid, hydrogen bonds in the water hold water molecule apart in an OPEN LATTICE structure .
( this is further average distance apart than when liquid, so same mass for more volume means less density )
- therefor ice floats
2) higher melting and boiling points
- (boiling pint ) because if hydrogen bonds mean more energy is needed to overcome then without would be just London
Remember structure for simole molecular why does it have low boiling
As the ATOMS are covalently bonded, but the molecules are attracted by weak London forced
These are the ones that are overcome, not much energy needed thus low boiling points
