Flashcards in 7.2 Ionisation Energies Deck (12)
Define first ionisation energy
The energy required to remove one electron from each atom in one mol of gaseous atoms to form one mol of gaseous 1+ ions
Define second ionisation energy
The energy required to remove an electron from each atom in one mol of gaseous 1+ ions to form one mol of gaseous 2+ ions
what electron is lost first?
Electron in the highest energy level / shell that experiences least nuclear attraction
3 Factors affecting ionisation energy and why
ATOMIC RADIUS - greater distance between nucleus and electron = less attraction = lower ionisation energy
NUCLEAR CHARGE - the more protons in the nucleus = greater attraction = higher ionisation energy
SHIELDING - inner electrons repel outer electrons causing shielding, reducing attraction
Why is the second ionisation energy higher than the first?
Because after the first electron is removed the remaining electrons at pulled closer to the nucleus, increasing the nuclear attraction
Ionisation energys allow us to predict?
The number of electrons in outer shell
The elements group
The elements identity
What do larger differences in the energies show?
The Jump from outer shell to inner shell
Trend in first ionisation energy down a group?
Decreases down a group because:
Atomic radius increases
More inner shells so shielding increases
Nuclear attraction on outer electrons decreases
Trend in first ionisation energies across a period?
Increases across a period because:
Nuclear charge increases
Same shell = similar shielding
Atomic radius decreases
Trend in periods 2 and 3?
There is a general increase across both period 2 and period 3. However they both fall in the same two places due to sub-shells, their energies and how orbitals fill with electrons
What are the falls in period 2 and what do they mark?
Be - B marks the start of the filling of the 2P sub shell
N - O marks the start of the electron pairing in the so originals of the 2P sub-shell