The atom and redox Flashcards
relative isotopic mass
mass of an isotope compared to 1/12 of the mass of carbon-12
relative atomic mass
weighted mean mass of an atom compared to 1/13 of the mass of carbon-12
first ionisation energy
the energy required to remove one mile of electrons from one mile of gaseous atoms
how to calculate relative atomic mass
(% × mass) + (% × mass)
———-
100
How to calculate relative formula/molecular mass
add the Ar values together
Ionisation energy trend down a group
ionisation energy decreases when you go down a group:
* sheilding increases as you go down
Ionisation energy trend across period 2 and 3
Ionisation energy increases:
*nuclear charge increases
Why is the second ionisation energy always larger than the first?
The whole atom has an overall positive charge it’s harder to remove an electron from a positive atom
and electrons are pulled closer to the nucleus as an electron is removed so distance decreases = more nuclear attraction
What happens to ionisation energy as you start a new shell e.g between Mg 2nd and 3rd ionisation energy?
Ionisation energy increases massively as the new shell has less shielding, and a smaller radius between the outer electron and nucleus, so nuclear attraction increases.
Why can there be small decreases in ionisation energy across a period?
s and p sub shell energies e.g between Be and B, a new sub shell started so more shielding and further distance between outer electron and nucleus.
p-orbital repulsion e.g between N and O, N has a half filled P orbital, which is more stable, when O loses its electron it gains a half full so becomes more stable so will lose that outer electron easier.
How many electrons can fill the first 4 shells?
2,8,18,32
Shape of s and p orbitals
an s orbital is a sphere
a p orbital is a dumbbell shape that can be along the x y or z axis.
order in which sub shells fill
1s 2s 2p 3s 3p 4s 3d 4p …
Why does the 3d orbital fill after the 4s?
The 4s orbital has a lower energy than 3d so is favoured to fill before the 3d orbital, however the electrons in 4s will be lost before those in 3d.
What is a degenerate orbital
orbitals of identical energy.
How does the s p d f relate to location in the periodic table.
s block - group 1 and 2
p block - group 3 4 5 6 7 8
d block - transition metals
f block - low part
How can both the 4s and 3d sub shells have electrons in but not be filled?
One electron in each 3d orbital is symmetrical and therefore more stable than expected. This extra stability more than compensates for the energy needed to promote an electron from the 4s sub shell.
define oxidation and in terms of oxidation number.
loss of electrons, increase in oxidation number
define reduction and in terms of oxidation number.
gain of electrons, decrease in oxidation number
oxidising agent
causing something to be oxidised, due to it being reduced itself.
reducing agent
causing something to be reduced, due to it being oxidised itself.
what is the oxidation number of uncombined elements
0
what is the oxidation number of group 1 elements
+1
what is the oxidation number of group 2 elements
+2
