Periodic Trend in Electron Configuration and Ionisation Energy Flashcards
What is the definition of the first ionisation energy?
The energy required to remove one mole of electrons from one mole of gaseous atoms to form 1+ ions
What is the equation for the first ionisation energy of element X
X(g) -> X+(g) + e-
REMEMBER: the number of the ionisation energy is the same number as the charge on the ion produced
What is the definition of ionisation energy
not first
The energy required to remove 1 electron from each ion in one mole of gaseous x+ ions in an element to form one mole of y+ions
What three things affect the attraction between outershell electron and nucleus which determine the trend in first ionisation energies?
-
Atomic/Ionic radius
2.Electron shielding
3.Nuclear Charge
What happens to the first ionisation energy as you go down the group?
It decreases
Why does the first ionisation energy decrease going down a group in the periodic table
- The atomic radius increases going down the group.
- This means that there are more inner shells so there is more electron shielding
- This reduces the attraction between the outershell electron and the nucleus
- This decreases the first ionisation energy
remember it is ALWAYS connecting to the attraction between the outershell electron and the nucleus.
Also the nuclear charge is neglible here bc/ it increases but is outweighed by the other two aspects
Why does the 1st ionisaiton energy increase as you go across a period in th eperiodic table?
- The nuclear charge increases as you go across the period (due to increasing number of protons)
- Since they are in the same shell, there is no increase in electron shielding
- This increases the nuclear attraction between outershell electron and nucleus
- This decreases the atomic radius
- This means a higher ionisation energy
Successive ionisation energies increase with [blank]
fill in the blank
Ionisation number
What predictions can be made using succesive ionisation energies?
The ionisation number that the largest jump happened from tells us:
1. How many electrons in the outershell of the element*
2. The group number of the element
*bc the large jump means that the next electron is being taken from a different shell, one closer to the nucleus as much more energy is required to remove it
Explain why there would be a large jump in succesive ionisation energies
1.The two electrons that the jump is between were removed from different shells.
2.The second electron (that the jump is between) has a stronger attraction to the nucleus because it is in a shell closer to the nucleus, and so more energy is required to remove the electron
3. Hence the higher ionisation energy
Explain why there may be a dip in 1st ionisation energies going across a period in the periodic table e.g. from Be to B
- Draw the electron configuration: In Be the outershell electron is removed from the 2s subshell, in B the outershell electron is removed from the 2p subshell
- The 2p subshell has a higher energy and is further away from the nucleus than 2s
- This means that less energy is required to remove the electron from the outershell of B, hence a lower ionisation energy
- What their configuration tells us ab/ which subshell their outer e- is taken from
- Which requires less energy and hence less ionisation energy to remove
Explain why there may be a dip in 1st ionisation energies going across a period in the periodic table, in the same subshell e.g. from N to O
- Draw the orbitals of the subshell. In N, the 3 2p orbitals eahc contain a single electron, in O, the highest energy electron is spin paired
- Spin paried electrons experience some repulsion, this decreases the attraction between the higher energy electron and the nucleus
- This means less energy is required to remove the highest energy electron, hence a lower ionisation energy
