unit 2 electron conf part ii ie and ea

7/28/2019 Unit 2 Electron Conf Part II IE and EA

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General Chemistry 1

MF008

Unit 2: Electronic Structure

Part II: Ionisation Energy & Electron Affinity


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Contd from Part I

If you find the term

Principle Quantum Number (n) it is the same asshell. It determines _______of orbital.

Angular Momentum Number (l) it is the same as

subshells. It determines _________of orbital Magnetic Quantum Number (mf) determines

orientation of ___________in space. Eg: px, py,

pz

Spin Quantum Number (ms) determines theproperty of______________. It has values

either +1/2 or -1/2

size

shape

orbital

electron


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Shell or the

Principle

Quantum

number (n)

Number of subshells

or the Angular

Momentumnumber (l)

Magnetic quantum

number (ml)

Number

Of

orbitals

Number

of

Electrons

1 0 (s) 0 1 2

2 0 (s) 0 1 2

2 1 (p) -1, 0, +1 3 6

3 0 (s) 0 1 2

3 1 (p) -1, 0, +1 3 6

3 2 (d) -2, -1, 0, +1, +2 5 10

4 0 (s) 0 1 2

4 1 (p) -1, 0, +1 3 6

4 2 (d) -2, -1, 0, +1, +2 5 10

4 3 (f) -3, -2, -1, 0, +1, +2, +3 7 14

Summary


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Question

An atom or ion is said to be in excited state if the electronic

configuration does not obey the Aufbau Principle

Electron configuration Excited Yes / No Correct Sequence

1s2

2s2

2p5

3s2

3p5

4s2

3d10

4p6

1s2 2s2 2p5 3s2 3p6

1s2 2s1 2p6 3s2 3p6 4s2


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Ionisation Energy (I.E)

Ionisation Energy is a measure of energy

required to __________ electrons from an

atom.

There are as many I.E. as there are

________________ in an atom.

eg: Na has 11 electrons so it has 11 I.E

that is 1st I.E, 2nd I.E., 3rdI.E and so forth..

remove

electrons


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Factors affecting I.E.

1. Nuclear charge The __________the nuclear charge, the _____________ the

attractive force of the nucleus on the electrons.

=>I.E __________ across a Period for s and p block elements

2. Atomic radius

The _____________the atom, the further is the outer shell electrons andthe _____________is the attractive force of the nucleus, so less energy isrequired.

=>I.E _____________down a Group in the Periodic Table

3. Shielding effect

Lower energy level electrons ____________the outermost electron from theattractive force of the atomic nucleus

=> I.E. _________________ down a Group in the Periodic Table

higher stronger

Increase

largerweaker

decrease

shield

decrease


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First Ionisation Energy (1st I.E)

Definition:

The energy required to remove _______ mole of

__________ from _______ mole gaseous

_____________ to form ____ mole of gaseous positive

ion.

Na(g) Na+(g) + e 1st I.E

Na+(g) Na 2+ (g) + e 2nd I.E

The stronger the pull of nucleus on the electron, the

________ energy needed to pull it out of the atom.

oneelectron one

atom one

greater


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Trend in I.E down group

Value ___________ down group.

Despite the _________ in nuclear charge due to

__________ number of protons in nucleus, the

outer shell electron is easier to remove.

This is due to __________ shielding and greater

_________ from nucleus. Outer electron is held _________ strongly and

thus __________ to remove.

decrease

increase

increase

greater

distanceless

easier


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Example 1

The successive I.E for removal of each electron from anoxygen atom

1310, 3400, 5300, 7500, 11000, 13000, 71300, 84100

There is a big increase in the energy required to removethe ________electron. The first _________electrons areremoved from the second shell (2s and 2p). The

___________electron is removed from the inner firstshell (1s)

=> From values of I.E, we can predict that element isin_____________

7th six

7th

Group 6


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Trend across period

I.E. generally ___________ across periodas __________________ is greater withone extra ____________.

The extra ___________ has gone into thesame ____________ level. So, not muchdifference in _______________ effect.

Increase ______________ makes electron___________ to remove.

increase

Nuclear charge

proton

electronenergy

shielding

attraction

harder


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Example 2

The first eight successive I.E for an element are as follows:

790, 1600, 3200, 4400, 16100, 19800, 23800, 23800

(a) How many electrons are there in the outer shell of theelement?

(a) In which group in the Periodic Table does the element

belong?

(a) Write down the electronic configuration of the element


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Electron Affinity (EA)

EA is the ___________ change when onemol of __________ is added to one mol of

______________ atoms or ions.

Just like IE, there is 1st EA, 2nd EA and so

forth.

Eg: Cl (g) + e Cl- (g)

energy

electron

gaseous


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Change in EA

First EA is usually _________ as energy is

released when an electron is

______________ to the nucleus.

Second EA is always _________ as

energy is required to overcome

electrostatic ___________ and add

another electron to a _________ ion.

negative

attracted

positive

repulsion

negative


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unit 2 electron conf part ii ie and ea

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