Electron arrangement and ionisation energies Flashcards
Defnintion of an element
A substance containing only 1 type of atom.
Definition of an atom
The samllest particle with all the chemical properties of an element.
Definition of an isotope
Atoms of the same element with different numbers of neutrons.
Definition of relative isotopic mass
The mass of an atom of an isotope comapred with 1/12th of the mass of an atom of carbon-12.
Definition of relative atomic mass
The average mass of an atom of an element compared with 1/12th of the mass of an atom of carbon-12.
Calculating relative atomic mass
Realtive atomic mass = (isotope abundance x isotope mass) + … / (sum of all isoptope abundances)
Method for determination of relative atomic mass
- A sample is placed in the mass spectometer.
- The sample is vaporised and then ionised to form positive ions.
- The ions are accelerated. Heavier ions move more slowly and are more difficult to deflect than the lighter ones, so the ions of each isotope are separated.
- The ions are detected on a mass spectrum as a mass-to-mass charge ratio m/z. Each ion reaching the detector adds to the signal, so the greater the abundance, the larger the signal.
Mass-to-mass ratio (m/z) =
relative mass of ion / relative charge on ion
Definition of a shell
A shell is a group of atomic orbitals in the same energy level.
Defintion of a sub-shell
A group of the same type of atomic orbitals within a shell.
Defintion of an atomic orbital
A region around the nucleus that can hold up to two electrons with opposite spins.
Description of s-orbital shape
Spherical
Description of p-orbital shape
Dumb-bell shape
Shell 1
Shell number- 1
Sub-shells present- S
Number of electrons in each sub-shell- 2
Total number of electrons in entire shell- 2
Shell 2
Shell number- 2
Sub-shells present- S and P
Number of electrons in each sub-shell- 2 (S) and 6 (P)
Total number of electrons in entire shell- 8
Shell 3
Shell number- 3
Sub-shells present- S, P and D
Number of electrons in each sub-shell- 2 (S), 6 (P) and 10 (D)
Total number of electrons in entire shell- 18
Shell 4
Shell number- 4
Sub-shells present- S, P, D and F
Number of electrons in each sub-shell- 2 (S), 6 (P), 10 (D) and 14 (F)
Total number of electrons- 32
Electronic configuration rule for transition metals
When transition metals form ions, they lose electrons from the 4s before the 3d sub-shell.
Definition of first ionisation energies
The energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous 1+ ions.
First ionisation energy equ for Li
Li (g) –> Li (g) + e-
Trend in first ionisation energies across a period
- General increase in first ionisation energies across the period.
- There are more protons in the nucleus (greater nuclear charge).
- The outer electron is in the same shell- no increase in shielding.
- An increase in nuclear attraction for the outer electron.
- Atom radii decreases, so the outer electron is closer to the nucleus.
- More energy is required to remove the outermost electron.
Trend in first ionisation energies fown a group
- The first ionisation energy decreases.
- More electron shells, so the outer electron is further from the nueclus.
- More electron sheilding (where inner electron shells repel outer shell electrons).
- Decreased nuclear attraction on outer shell.
- The number of protons increases but this is far outweighed by the increased shielding.
- Less energy required to remove outermost electron (the outer electrons are held less tightly).
Definition of successive ionisation energies
A measure of the energy required to remove each electron in turn from an atom.
Process of successive ionisation energies
Electrons are removed from the same atom starting from the outer electron and working in. The data is used to identify the atom.
Successive ionisation energies increase due to…
- The numberof protons remaining the same but proton to electron ratio is increasing.
- There’s more nuclear attraction on remaining electrons.
