7.2 Ionisation Energies Flashcards Preview

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Flashcards in 7.2 Ionisation Energies Deck (12)
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Define first ionisation energy

What unit?

The energy required to remove one electron from each atom in one mol of gaseous atoms to form one mol of gaseous 1+ ions

KJmol -1


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


How does the pairing of orbitals in sub shells cause fall in ionisation energy?

The paired electrons repel and make it easier for them to be removed