Atomic Structure Flashcards
On the Periodic Table which is the
a) Mass Number
b) Atomic Number?
a) the big number - it is the total number of protons and neutrons
b) the little number - it is the number protons (sometimes known as the Proton Number)
What is an isotope?
An atom of the same element with the same number of protons but a different number of neutrons
Why do isotopes of the same element have the same chemical properties?
They have the same number of outer electrons
Do isotopes of the same element have the same physical properties?
Why?
No - they have different physical properties because they have a different number of neutrons and therefore different masses so boiling/ melting points are different
Describe the electron configuration of an atom
Electrons are held in Principal Energy Levels, which are given the numbers 1,2,3…
Principal Energy Levels are divided into sub-levels, which are assigned the letters s,p,d,f
Sub-Levels are further divided into orbitals and each orbital holds a maximum of 2 electrons
List the sub-Levels in order of Energy, from lowest to highest
s -> p -> d -> f
How many orbitals does an s sub level have
1
How many orbitals can a p sub level hold?
3
How many orbitals can a d sub level hold
5
How many orbitals can a f sub level hold
7
What is the maximum number of electrons in principal energy level:
a) 1
b) 2
c) 3
d) 4
Which rule applies to this?
a) 2
b) 8
c) 18
d) 32
The 2n squared rule
What is the order in which the energy levels are filled?
1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p6, 5s2, 4d10, 5p6
What rule applies to 4s?
It fills before 3d as it is lower in energy but, when ionised, electrons are removed from 4s before 3d
True or false:
Electrons fill the orbital of lowest energy first
True
What is the electron configuration of Chromium? (24 electrons)
Why is it different?
1s2, 2s2, 2p6, 3s2, 3p6, 4s1, 3d5
This is a more stable arrangement and is of lower energy
What is the electronic configuration of Copper? (29 electrons)
Why is this different?
1s2, 2s2, 2p6, 3s2, 3p6, 4s1, 3d10
The structure is of lower energy and represents a more stable arrangement
What do paired electrons in an orbital have
Opposite spin
Which is block
s
p
d
f
On the periodic table
s= group 1&2 p= group 3-0 d= transition metals f = the bottom two
How to determine the electronic configuration using the table
The period number is the PEL number, d-block elements PEL number is “period minus 1”
The block letter becomes the sub-level
The column it is in within that block is the ‘power of’ number
Define First Ionisation Energy
The minimum amount of energy required to remove one electron from a gaseous atom
What factors affect the amount of energy needed to ionise an atom?
Size of atom - number of PELs and number of protons
Attraction between nucleus and outer electron -affected by size, shielding and number of protons
Repulsion between paired electrons
As you travel down a group what happens to the size of each atom?
Why?
What does this mean for the outer electron?
What happens to ionisation as you go down?
It increases because there are more PELs
It is further from the nucleus so there is less attraction and there will be more shielding
First Ionisation energy decreases
Generally what happens to first ionisation energy as you go across a period?
Why?
It increases
Same shielding, increasing number of protons- increased nuclear charge and stronger attraction between nucleus and outer electron.
Atomic radius decreases
More energy needed to remove outer electron
Why does ionisation energy decrease for group 3 elements across a period?
Group 3 is in the p block
P is higher energy than S so group 3 elements have electrons which are further from the nucleus and so there is less attraction
