Electron Structure Flashcards
Where are electrons found
3D regions of space called orbitals
What is Heisenberg’s uncertainty principle
We can never be exactly sure where an electron is
How many electrons fill the first 4 shells?
2,8,18,32
Maximum number of electrons in a shell’ n’ is given by the formula …
2n^2
Shells - energy
Regarded as energy levels
Energy increases as the shell number increases
What’s the principal quantum number
The number representing the overall energy of each orbital or shell( shell number)
So n=2 is the second shell
What is an orbital
A region that can hold up to 2 ELECTRONS
OPPOSITE spins
3D region of space in which there is a >95% chance of finding an electron
What are sublevels
Have electrons orbitals
Each initial can hold 2 electron
S orbitsl
The electron cloud is within the shape of a sphere
Each shell from n=1 contains ONE s orbital
The greater he shell number n, the greater the radius of its s orbital
2 orbitals in sun level
P orbital
Electron cloud is within he shape of a dumb bell
3 p orbitals at sub- shell level
Each shell from n=2 contains 3 p orbitals
The greater the shell number ‘n’, the further the p orbtial is from the nucleus
6= MAX no. Of electrons in sublevel
What is the order of number of sublevels in orbitals from s-p-d-f
1,3,5,7
TIMES BY 2 FOR 2 ELECTRONS
D orbital
Each shell from n=3 contains 5 d orbitals
Max no. Of electrons in shbshell =10
F orbital
Each shell from n=4 contains 7 f orbitals
Max number of electrons in shbshell is 14
What are subshells/ levels
Within a shell, orbitals of the SAME type( p,f,s etc) are grouped together as subshells
In SHELLS
Subshells of s, p, d and f
The periodic table- shells
The periodic table is split into BLCOKS
A s block element is one whose outer electron is filling a s - sub shell , highest energy electron is s subshells
3 rules for how orbitals are filled?
- electrons pair with opposite spins
- orbitals fill in order of increasing energy
- orbitals with the same energy are occupied singly first
Orbitals fill in order of increasing energy
- aufbau principle
- the subshells that make up shells have slightly different energy levels
Within each shell, the new type of sub shell added has a HIGHER energy
The 3D subshell is at a HIGHER energy than the 4s subshell, so the 4s fills first - 3p,4s,3D
Electrons pair with opposite spins
Each orbital can hold up to TWO electrons
Electrons are negatively charged and repel one another
They have a property called SPIN - either up or down
An electron is shown as an arrow, showing its spin. Either UP or down
Opposite spins help counteract with repulsion between negative charged of 2 electrons
Orbitals with the same energy are occupied singly first
Within a subshell, the orbitals have the same energy
One electron occupies each orbital before pairing starts , this prevents ANy repulsion between paired electrons until there is no further orbital available at the same energy level
HUNDS RULE
Exceptions to normal electron configuration
Cr and Cu
Cr
1s^2 2s^2 2p^6 3s^2 3p^6 4s ^1 3D ^5
Cu
1s^2 2s^2 2p^6 3s^2 3p^6 4s^1 3d^10
Why are Cr and Cu exceptions
the arrangements are slightly lower energy arrangements as the reduced electron electron repulsion makes up for the fact that one electron is in a slightly higher energy level
Electron configuration? How do the orbitals go?
1s 2s 2p (3) 3s 3p 4s 3d (5) 4p
Group 8 elements - electrons in outer shell
He -2
Ne - 10
Ar-18
E.g. oxygen - {he} 2s^2 2p^4
If you have to draw the electron structure for ions, (boxes) how do you do it?
Fill up the orbitals for the ion as their atoms
Take out any 4s electrons first
Then remove further electrons from 3 d
Why do you remove 4s electrons before 3D - ions
Once filled, the 3D energy level falls below the 4s energy level, so it empties before 3D subs hell , (because it’s at a Lower energy level than 3D subs hell before - fills first)
