topic 3 - first ionisation energy + trends Flashcards

1
Q

Ionisation energy

A

First ionisation energy is the amount of energy needed to remove 1 mole of outer electrons from 1 mole of gaseous atoms to form 1 mole of positive ions​

X(g) → X+(g) + e-

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2
Q

Trends across the periods​

A

Increase across the period because nuclear charge increases. shielding due to inner shells stay the same

Electrostatic attraction of nucleus + outer electrons increase

Anomiles
group 3 electron removed higher energy sub shell
Group 6 electrons pair up and repel in an orbital

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3
Q

Period 2 - Li and Be

A

In Li and Be the outer electrons are being removed from the 2s orbital​

There is an increase in 1st IE from Li to Be as there are more protons in Be so there is a greater attraction (it is harder to remove the outer electron)

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4
Q

Period 2​ - boron

A

In Boron, the outer electron is being removed from the 2p orbital. ​

This is a higher energy orbital than the 2s so it is shielded by the 2s electrons​

This makes the 2p electron easier to remove so there is a drop in 1st IE

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5
Q

Period 2 - Carbon and Nitrogen

A

In Carbon and Nitrogen, the outer electrons are also being removed from the 2p orbital​

These electrons are unpaired​

These elements show the expected increase in 1st IE due to the increasing nuclear charge​

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6
Q

Period 2​ - oxygen

A

In oxygen, the outer electron is being removed from the 2p orbital BUT it is paired with another electron​

The repulsion between these electrons makes it easier to remove one​

This causes a decrease in 1st IE​

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7
Q

Period 2 - Fluorine and Neon

A

In Fluorine and Neon the outer electrons are also being removed from pairs in the 2p orbital​

They show an increase in 1st IE due to increased nuclear charge

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8
Q

Period 3

A

There is a similar pattern in period 3 1st IE with electrons being removed from the 3s and 3p orbitals

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9
Q

Period 4

A

The pattern in period 4 is similar for groups 1 to 7 and 0, with dips at group 3 and 6​

The 1st IE of the transition metals increases across the period but only slightly as there is a shielding effect from the 3d orbital​

The outer electron from a transition metal always comes from the 4s orbital as this is higher energy than the 3d​

This means the increasing number of 3d electrons provide shielding and cancel out the effect of the additional proton

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10
Q

Trends down groups​

A

As groups descend 1st ionisation energy decreases

Because outer electron being removed further from nucleus there are more inner shells to shield the outer electron

Electrostatic attraction to nucleus is less

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