7.2 Ionisation Energies Flashcards Preview

OCR Chapter 7 Chemistry (AS) > 7.2 Ionisation Energies > Flashcards

Flashcards in 7.2 Ionisation Energies Deck (12)
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1

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

2

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

3

what electron is lost first?

Electron in the highest energy level / shell that experiences least nuclear attraction

4

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

5

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

6

Ionisation energys allow us to predict?

The number of electrons in outer shell
The elements group
The elements identity

7

What do larger differences in the energies show?

The Jump from outer shell to inner shell

8

Trend in first ionisation energy down a group?

Why?

Decreases down a group because:

Atomic radius increases

More inner shells so shielding increases

Nuclear attraction on outer electrons decreases

9

Trend in first ionisation energies across a period?

Increases across a period because:

Nuclear charge increases

Same shell = similar shielding

Atomic radius decreases

10

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

11

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

12

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