Unit 1.2 Basic Ideas about Atoms (Electronic Structure, Ionisation and Spectra) Flashcards
How do electrons in an atom orbit the nucleus?
The electrons in an atom orbit the nucleus in ‘shells’ or ‘energy levels’
The first energy level can hold up to two electrons.
The second energy level can hold up to eight electrons.
Energy levels are subdivided into ____________.
Energy levels can be subdivided into ‘orbitals’ which can each hold up to two electrons.
What is the condition for the electrons to occupy the same energy level?
To occupy the same orbital, the two electrons must have opposite ‘spins’.
One must be ‘spin up’ and the other ‘spin down’.
Define orbital.
A region of space within an atom that can hold up to two electrons with opposite spins.
Why can the first energy level hold two electrons?
Because it contains only one orbital.
The orbitals in the first energy level fill before the orbitals of the second energy level.
How are orbitals grouped together?
Inside energy levels, orbitals are grouped together in ‘subshells’.
The subshells are called:
s, p, d, f and g
and contain orbitals of the same name.
E.g. the 3x subshell is in the third energy level and contains s orbitals.
Orbitals in different subshells have different shapes.
Describe the shape of the s orbital.
s orbitals are spherical.
Every energy level contains one s orbital.
Describe the shape of the p orbital.
p orbitals have dumbbell shapes. The second and subsequent energy levels contain 3 p orbitals which have the same shape but point along different axes.
They can be labelled individually as px, py and pz.
Describe the shape of the d, f, and g orbitals.
d, f and g orbitals have increasingly complex shapes
Describe the arrangement of electrons in energy levels.
Electrons occupy certain fixed energy levels.
Each atom has its own unique set of energy levels which depend on the number of protons and electrons in the atom.
Energy levels in an atom can be numbered from 1 to infinity. 1 is the lowest energy level (closest to the nucleus) and energy level infinity corresponds to the energy of an electron which is not attracted to the nucleus at all.
Energy levels converge as they approach infinity.
How many orbitals does the s subshell have?
one s-orbital
The s-subshell can hold 2 electrons
How many orbitals does the p-subshell have?
three p orbitals.
The p subshell can hold 6 electrons
How many orbitals does the d subshell have?
five d orbitals
The d subshell can hold 10 electrons
How many orbitals does the f subshell have?
seven f orbitals
The f orbital can hold 14 electrons.
Why must the 4s subshell be filled before the 3d subshell?
Since the different subshells have different energies and the energies of the different levels get closer together with increasing energy level number, the high energy sub-shells of some energy levels soon overlap with the low energy subshells of higher energy levels.
The 4s subshell is at a lower energy level than the 3d subshell, so, must be filled first.
List the 3 rules which determine the way in which electrons fill the orbitals.
- Electrons always fill the lowest energy orbitals first
- Electrons never pair up in the same orbital until all orbitals of the same energy are singly occupied, and all unpaired electrons have parallel spin.
- Only two electrons may occupy the same orbital and they must have opposite spin
List the number of orbitals for each subshell.
n=1: 1s
n=2: 2s, 2p
n=3: 3s, 3p, 3d
n=4: 4s, 4p, 4d, 4f
Tell me the electron configuration of Cr.
1s2, 2s2, 2p6,3s2, 3p6, 3d5, 4s1
Tell me the electron configuration of Cu.
1s2, 2s2, 2p6, 3s2, 3p6, 3d10, 4s1
In what order are the electrons removed during the process of making ions?
- Remove outer shell electrons first
- Remove p electrons first, then s-electrons and then d-electons
- Remove paired electrons before unpaired electrons in the same subshell.
In most cases, these rules mean electrons are removed from the most recently filled orbital.
However, this is bot true for the elements in the d-block.
Although electrons go in to the 4s subshell before they go in to the 3d, when d-block elements form ions electrons are removed from the 4s subshell first and them from the 3d.
What happens if we supply the atom with additional energy?
The electrons can use this energy to jump into higher energy levels.
How is additional energy supplied to the atom?
The energy is provided in the form of light energy.
What happens when an electron falls from a higher energy level to a lower energy level?
When an electron falls from a higher energy level to a lower energy level, it releases additional energy, again in the form of light energy.
Electrons can only move between energy levels by absorbing or emitting light with exactly the right energy.
What does the amount of energy carried by a light wave depend on?
Its frequency and wavelength, hence its colour
