THE ATOMTHE ATOM

PHYSICAL SCIENCEPHYSICAL SCIENCE

GRADE 10GRADE 10

K WARNEK WARNE

Development of the atomic theory The idea that everything is made up of a few simple parts originated during

the 400's B.C. in the philosophy of atomism. Atomism was founded by the Greek philosopher Leucippus, but his disciple Democritus developed the philosophy more fully. Democritus gave his basic particle the name ……., which means …………………... He imagined atoms as small, hard particles, all composed of the same substance but of different sizes and shapes. During the 300's B.C., a Greek philosopher named Epicurus incorporated Democritus's ideas about atoms into his philosophy. About 50 B.C., the Roman philosopher and poet Lucretius presented the fundamental principles of atomism in his long poem, On the Nature of Things.

During the Middle Ages, the idea of atoms was largely ignored. This neglect resulted partly from the fact that atomism had been rejected by Aristotle, an ancient Greek philosopher whose theories dominated medieval philosophy and science. The idea that atoms form the ……………………….. of all matter did survive, however. During the 1500's and 1600's, such founders of modern science as Francis Bacon and Isaac Newton of England and Galileo of Italy believed in atoms. But those scientists could add little more to the atomic theory than Democritus had described.

Development of the atomic theory The idea that everything is made up of a few simple parts originated during

the 400's B.C. in the philosophy of atomism. Atomism was founded by the Greek philosopher Leucippus, but his disciple Democritus developed the philosophy more fully. Democritus gave his basic particle the name atom, which means uncuttable. He imagined atoms as small, hard particles, all composed of the same substance but of different sizes and shapes. During the 300's B.C., a Greek philosopher named Epicurus incorporated Democritus's ideas about atoms into his philosophy. About 50 B.C., the Roman philosopher and poet Lucretius presented the fundamental principles of atomism in his long poem, On the Nature of Things.

During the Middle Ages, the idea of atoms was largely ignored. This neglect resulted partly from the fact that atomism had been rejected by Aristotle, an ancient Greek philosopher whose theories dominated medieval philosophy and science. The idea that atoms form the basic units of all matter did survive, however. During the 1500's and 1600's, such founders of modern science as Francis Bacon and Isaac Newton of England and Galileo of Italy believed in atoms. But those scientists could add little more to the atomic theory than Democritus had described.

The birth of the modern atomic theory.In 1750, Rudjer Boscovich, a scientist born in what is now Croatia,

suggested that Democritus might have been wrong in believing that atoms are "uncuttable." Boscovich thought that atoms contain smaller parts, which in turn contain still smaller parts, and so forth down to the fundamental building blocks of matter. He felt that these building blocks must be geometric points with no size at all. Today, most atomic physicists accept a modern form of this idea.

The development of the atomic theory advanced greatly when chemistry became an exact science during the late 1700's. Chemists discovered that they could combine elements to form compounds only in certain ……… proportions according to …….. In 1803, a British chemist named John Dalton developed an atomic theory to explain this discovery.

The birth of the modern atomic theory.In 1750, Rudjer Boscovich, a scientist born in what is now Croatia, suggested that

Democritus might have been wrong in believing that atoms are "uncuttable." Boscovich thought that atoms contain smaller parts, which in turn contain still smaller parts, and so forth down to the fundamental building blocks of matter. He felt that these building blocks must be geometric points with no size at all. Today, most atomic physicists accept a modern form of this idea.

The development of the atomic theory advanced greatly when chemistry became an exact science during the late 1700's. Chemists discovered that they could combine elements to form compounds only in certain FIXED proportions according to MASSIn 1803, a British chemist named John Dalton developed an atomic theory to explain this discovery. *

* Information taken from a variety of sources – including Wikipedia.

Atomic Theory PresentationMany scientists contributed to the development of the modern atomic theory,

including: Dalton, Thomson, Rutherford, Chadwick, Bohr, De Broglie, Schrodinger, Heizenberg, Pauli

Research the contribution of any one of the scientists listed above and present your findings in a 3 minute presentation.

• You must use the headings applicable to any scientific investigation: – Theory/Background, Aim, Apparatus, Method/Experiments, Results,

Conclusions,

– If no information is available for a particular heading then just state “No information available.”

– Evaluation (Yours): Give your impression of the impact the particular person had on atomic theory development.

Information can be taken from lessons or your textbooks as well as other sources BUT must be given in your OWN WORDS!

ATOMIC THEORY PRESENTATION RUBRIC NAME: ________________________

ITEMS Required Detail MARKS>> 0 1 2 3 MARK

Scientist chosen from list:

Dalton, Thomson, Rutherford, Chadwick, Bohr, De Broglie, Schrodinger, Heizenberg, Pauli

No Yes

 

   

Timing 3 minutes <1 / >5

1/5 2/4 3  

Presentation SkillsEye contact, knowledge, confidence, voice intonation, engaging/dynamic

nonesom

emost all  

Presentation AidsAppropriate/correct, neat, attractive, stimulating, variety

nonesom

emost all  

Scientific Investigation Headings

Theory/Background, Aim, Apparatus, Method/Experiments, Results, Conclusions,

nonesom

emost all  

Evaluation personalOwn impression, impact on atomic theory development, coherent reasoning, impressive/thoughtful

nonesom

emost all  

Evidence of own input % which appears original nonesom

emost all  

 TOTAL  

The birth of the modern atomic theory.

Dalton proposed that each element consists of a ……………. ……………..of atom and that the varying properties of the elements result from differences in their atoms.

He further suggested that all atoms of a given element are ………………….. in size, shape, and mass.

According to Dalton's theory, when atoms combine and form a particular compound, they always combine in a …………… ………………………. As a result, the composition by mass of a particular compound is always the same.

The birth of the modern atomic theory.

Dalton proposed that each element consists of a particular kind of atom and that the varying properties of the elements result from differences in their atoms.

He further suggested that all atoms of a given element are identical in size, shape, and mass.

According to Dalton's theory, when atoms combine and form a particular compound, they always combine in a specific numerical ratio. As a result, the composition by mass of a particular compound is always the same.

The electrical nature of matter• Thompson’s experiments

with …………… ray tubes led to the discovery of ……………. in atoms.

• He advanced the model of the atom to include positive and negative charges in the “…………………..” model.

The electrical nature of matter• Thompson’s experiments

with cathode ray tubes led to the discovery of charges in atoms.

• He advanced the model of the atom to include positive and negative charges in the “current bun” model.

Radioactivity• Radioactivity is the ............................ emission of

…………………….(sub atomic particles) from some materials.

• The discovery of radioactivity led to the realization that atoms were …………………….

QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.

Radioactivity• Radioactivity is the spontaneous emission of radiation (sub atomic

particles) from some materials. Marie Curie• The discovery of radioactivity led to the realization that atoms were

not indivisible.

Radioactivity• While she was studying for her doctorate, Henri Becquerel sent her

samples of a uranium salt that had left an impression on x-ray film, .......................................................... in which they were contained.

• Do you have a watch with hands that glow? Radium was the first substance used to make the watch hands glow. Women were hired to brush radium paint onto the tiny watch hands. The problem was that the brush head was unmanageable and the women licked the brush to keep the head nice and pointy. Their tongues eventually fell off, and that was only the beginning. ..........................and ......................... followed. And then eventually death.

• With Radium selling at ........................................ a pound (back in the twenties) doctors everywhere were investing in this wonderful cancer cure. A “cure” that caused cancer and leukemia.

Radioactivity• While she was studying for her doctorate, Henri Becquerel sent her

samples of a uranium salt that had left an impression on x-ray film, through the envelope in which they were contained.

• Do you have a watch with hands that glow? Radium was the first substance used to make the watch hands glow. Women were hired to brush radium paint onto the tiny watch hands. The problem was that the brush head was unmanageable and the women licked the brush to keep the head nice and pointy. Their tongues eventually fell off, and that was only the beginning. Leukemia and bone cancer followed. And then death.

• With Radium selling at ten million dollars a pound (back in the twenties) doctors everywhere were investing in this wonderful cancer cure. A “cure” that caused cancer and leukemia.

Rutherford’s experiment• Rutherford shot ................... particles at very thin gold

foil.• Most of the radiation ........................................• Some radiation was .................................. - by significant

amounts.

Rutherford’s experiment• Rutherford shot alpha particles at very thin gold foil.• Most of the radiation went straight through.• Some radiation was deflected - by significant

amounts.

Rutherfords ModelRutherford’s model has the

electrons moving in orbits around a very dense core.

• The core consists of ................ (....) - this would have caused the massive ........................... he had observed.

• The ........................... orbit at a large distance from the nucleus - this explains why much of the radiation ..............................the gold foil.

• No of electrons = no. of protons

Protons - in the nucleus

electrons

Rutherfords ModelRutherford’s model has the electrons

moving in orbits around a very dense core.

• The core consists of protons (+) - this would have caused the massive deflections he had observed.

• The electrons orbit at a large distance from the nucleus - this explains why much of the radiation passed through the gold foil.

• No of electrons = no. of protons

Protons - in the nucleus

electrons

Rutherfords Model - problemsRutherford’s model could not

explain:

• Why the electrons did not lose energy as they orbited.

• What held the protons together in the nucleus.

• The origins of __________ _______ of gases could not be explained.

Protons - in the nucleus

electrons

Rutherfords Model - problemsRutherford’s model could not

explain:

• Why the electrons did not lose energy as they orbited.

• What held the protons together in the nucleus.

• The origins of emission spectra of gases could not be explained.

Protons - in the nucleus

electrons

Atomic Structure RevisionELEMENT SYMBOL Z (ATOMIC

NUMBER)A (MASS NUMBER)

NEUTRONS ELECTRONS

TOT VALENCE

Hydrogen H 1 1 0 1 1

Lithium Li 3 7 4 3 1

Carbon C 6 12 6 6 4

Nitrogen N 7 14 7 7 5

O

Ne

Na

Ar

Ca

Fill in the missing information for each of the elements above – note any patterns that begin to develop.

Atomic Structure RevisionELEMENT SYMBOL Z (ATOMIC

NUMBER)A (MASS NUMBER)

NEUTRONS ELECTRONS

TOT VALENCE

Hydrogen H 1 1 0 1 1

Lithium Li 3 7 4 3 1

Carbon C 6 12 6 6 4

Nitrogen N 7 14 7 7 5

O

Ne

Na

Ar

Ca

Fill in the missing information for each of the elements above – note any patterns that begin to develop.

THE NEUTRAL ATOM

Notation

Z

AXAtomic Number

(smaller)

Mass Number (bigger) symbol

• Atomic Number Z = number of protons (& electrons)

• Mass number A = protons + neutrons.

• Number of neutrons = A - Z

Atomic Theory through the ages.

Atomic Theory through the ages.

Line Spectra

Gases absorb certain frequencies of light.

Each gas absorbs a unique combination of frequencies – each frequency corresponding to a unique colour.

So each gas has a unique set colours which is known at its “line spectra” – because they are unique they can be used to identify a gas – similar to fingerprints.

Line SpectraGases absorb certain frequencies of light.

Each gas absorbs a unique combination of frequencies – each frequency corresponding to a unique colour.

So each gas has a unique set colours which is known at its “line spectra” – because they are unique they can be used to identify a gas – similar to fingerprints.

Bohr’s AtomBohr - brought the concept of

quantization into atomic theory.Electrons could only move in certain

specific orbits corresponding to specific amounts of energy.

These ENERGY LEVELS radiated out from the nucleus with higher energies being further away.

Electrons do not radiate energy in these orbits.

Energy is gained or lost when they move between orbits.

This model enabled Bohr to explain the hydrogen spectrum.

Atomic SpectraA glass prism can be used to generate a colour …………………..

If this the light generated by a hot (glowing) gas is viewed through a prism specific colour lines are seen as AN ……………… ………….SPECTRUM.

If light is shone through a cold sample of the same gas, the same specific colour lines are absent and appear as an ……………………….. LINE SPECTRUM.

Atomic SpectraA glass prisim can be used to generate a colour spectrum.

If this the light generated by a hot (glowing) gas is viewed through a prism specific colour lines are seen as AN EMISSION LINE SPECTRUM.

If light is shone through a cold sample of the same gas, the same specific colour lines are absent and appear as an ABSORPTION LINE SPECTRUM.

Absorption & Emission spectrum

• In absorption spectrum radiation is again absorbed by electrons being …………… to higher energy levels.

• The same frequencies (colours) are again emitted when the excited electrons ……………………. to the ground state in an ………………………spectrum.

---- …………………………………………………

Absorption & Emission spectrum

• In absorption spectrum radiation is again absorbed by electrons being excited to higher energy levels.

• The same frequencies (colours) are again emitted when the excited electrons drop down to the ground state in an emission spectrum.

---- EMITTED LIGHTABSORBED LIGHTABSORBED LIGHT

Emission SpectrumExcited electrons dropping down from unstable energy levels ……………………..in the form of light.

The frequency (colour) of the radiation is directly related to the ……………………….. between the energy levels.

Since each element has its own ……………………series of energy levels, each element also has its own unique series of …………………………… lines.

The line spectrum can therefore be used to …………………each element much like a fingerprint.

Emission Spectrum

Excited electrons dropping down from unstable energy levels radiate energy in the form of light.

The frequency (colour) of the radiation is directly related to the energy gap between the energy levels.

Since each element has its own unique series of energy levels, each element also has its own unique series of emission/absorption lines.

The line spectrum can therefore be used to identify each element much like a fingerprint.

THE NEUTRAL ATOM• The atom consists of a _____________________

______________________________ surrounded by a __________________________.

• Atomic Number Z: ___________________ in the Nucleus = _________________ in a ______ atom.

• Mass number A - Number of ______ + ________

Notation

Z

AX______________ Number

(smaller)

___________ Number (bigger) symbol

THE NEUTRAL ATOM• The atom consists of a nucleus containing protons

and neutrons surrounded by a cloud of electrons.

• Atomic Number Z - Number of protons in the Nucleus = number of electrons in a neutral atom.

• Mass number A = Number of protons + neutrons.

Notation

Z

AXAtomic Number

(smaller)

Mass Number (bigger) symbol

Relative Masses• Relative atomic(Ar): The mass of the atom relative to

________________________________________. (Number of times heavier than…)

Eg: O - 16 one atom of oxygen is ________________ than 1/12 of the mass of a C12 atom,

Formula mass (Mr) - The _______________________ of the atoms in a molecule.

Water H2O one molecule of water has a relative mass of _____________________________ that is the molecular or formula mass of water.

Mr(H2O) = 18 (Times heavier than…)

Relative Masses

• Relative atomic mass (Ar): The average mass of an atom of an element relative to 1/12 of the mass of a C12 atom. (Number of times heavier than…)

Eg: O - 16 one atom of oxygen is 16 times heavier than 1/12 of the mass of a C12

atom.

• Formula mass (Mr) - The sum of all the atomic masses of the atoms in a molecule.

Water H2O one molecule of water has a relative mass of (2x(1)+16) = 18 - that is the molecular or formula mass of water.

Mr(H2O) = 18 (Times heavier than…)

Relative Masses - examples

Calculate the Formula masses of:• O2 (oxygen gas) Mr(O2) = • Cl2 (chlorine gas)• NaCl (sodium chloride - table salt)

• CaCO3 (calcium carbonate)

• (NH4)2Cr2O7 (ammonium dichromate)

Relative Masses - examples

Calculate the Formula masses of:• O2 (oxygen gas) Mr (O2) = 2x16 = 32• Cl2 (chlorine gas) Mr (Cl2) = 2x35.5 = 71.0• NaCl (sodium chloride - table salt)

Mr (NaCl) = 23+35.5 = 58.5• CaCO3 (calcium carbonate)

Mr (CaCO3) = 40.1+12+(3x16) = 100.1• (NH4)2Cr2O7 (ammonium dichromate)

Mr ((NH4)2Cr2O7 ) = 2(14+4)+2(52)+7(16) = 252

Isotopes

Isotopes Atoms of the same element which have different numbers of

neutrons. Others – Boron 10 & 11, Hydrogen 1 & 2, Chlorine 35 & 37. Write notation and work out numbers of neutrons.

e- e-

e- e-e-

e- e- e-

e- e-e-

e-

The two atoms below both belong to carbon but they are not identical – can you spot what is different?

612C 6

13C

Isotopes

Isotopes Atoms of the same element which have different numbers of

neutrons. Others – Boron 10 & 11, Hydrogen 1 & 2, Chlorine 35 & 37. Write notation and work out numbers of neutrons.

e- e-

e- e-e-

e- e- e-

e- e-e-

e-

The two atoms below both belong to carbon but they are not identical – can you spot what is different?

612C 6

13C

510B 5

11B 1735Cl 17

37Cl 11H 1

2H

Isotopes• Isotopes - Atoms of the _______________ which

have different _____________________________________.

Eg: 613C & 6

12C

• 37Cl (25%) & 35Cl (75%) - ratio _________

Av Ar(Cl) =

Or

Av Ar(Cl) = Relative atomic mass is (actually) the ____________ mass of an atom of an element

relative to 1/12 of the mass of a carbon-twelve atom.

Isotopes• Isotopes - Atoms of the same element which have

different numbers of neutrons. Eg: 613C & 6

12C

• 37Cl (25%) & 35Cl (75%) - ratio 1:3

Av Ar(Cl) = (37x25)+(35x75) = 35.50100Or

Av Ar(Cl) = (37x1)+(35x3) = 35.504

Relative atomic mass is (actually) the average mass of an atom of an element relative to 1/12 of the mass of a carbon-twelve atom.

Bohr’s Atom - problems• Only explain ____________

_______________

• Could not explain __________ _______________________ or formation or properties.

• Why ________________ and ___________________ in orbits.

• At variance with ___________ ______________________.

Heisenberg: Not possible to know _________________________________ at the same _______________ with the same _______________________.

Bohr’s Atom - problems• Only explain hydrogen

spectrum.

• Could not explain molecules (bonding of atoms) - formation or properties.

• Why fixed orbits and no energy radiation in orbits.

• At variance with Heisenberg’s uncertainty principle.

Heisenberg: Not possible to know both the position and velocity of an electron at the same time with the same amount of accuracy.

A Wave Model• De Broglie - light - ‘_____

______________’ - theory.

• Davisson & Germer - electron diffraction -proof of ‘__________________’.

• Shroedinger, Heisenberg et. al. - __________________ mechanical model.

• Orbits ---> ________________- standing electron ____________ - a ___________________ defining the standing wave pattern.

Orbital: - a region where there is a __________________ of finding an electron.

A Wave Model• De Broglie - light - ‘matter

wave’ - theory.• Davisson & Germer - electron

diffraction -proof of ‘matter waves’.

• Shroedinger, Heisenberg et. al. - wave & quantum mechanical model.

• Orbits ---> Orbitals - standing electron waves - a region or space defining the standing wave pattern.

Orbital: - a region where there is a high probability of finding an electron.

Ionisation Energy (Ei)The ____________________________ to REMOVE AN ELECTRON completely from an atom.

Na: 1s22s22p63s1 Na+: 1s22s22p6Electronic structure

FIRST ionisation energy (Ei1): Energy required to remove _______________ electron. ______ ____________

SECOND ionisation energy (Ei2): Energy required to remove ____________ __________ electron. ______ ____________

Ionisation Energy (Ei)The ENERGY REQUIRED to REMOVE AN ELECTRON completely from an atom in the GAS phase.

Sodium atom

Sodium ion

Na: 1s22s22p63s1 Na+: 1s22s22p6Electronic structure

FIRST ionisation energy (Ei1): Energy required to remove OUTERMOST electron. M(g) M+ (g) + 1e-

SECOND ionisation energy (Ei2): Energy required to remove SECOND OUTERMOST electron. M+(g) M2+(g) + 1e-

Successive Ionization EnergiesAnalyse this graph in light of your knowledge of atomic & electronic structure. This graph can be used to provide ‘evidence’ for some of the features of modern atomic theory.

What can be inferred about the electronic structure of the atom?

4s

3s

2s

1s

3p

2p

Al 1s2

What can be inferred about the electronic structure of the atom?

Successive Ionization EnergiesFIRST ionisation energy (Ei1): Energy required to remove OUTERMOST electron. M M+ + 1e-

SECOND ionisation energy (Ei2): Energy required to remove SECOND OUTERMOST electron. M+ M2+ + 1e-

Inner level

Hard to remove close to nucleus

Second energy level

Outer (valence) level

Easy to remove far from the nucleus

This graph provides EVIDENCE for energy levels.

What can be inferred about the electronic structure of the atom?

Successive Ionization EnergiesFIRST ionisation energy (Ei1): Energy required to remove OUTERMOST electron. M M+ + 1e-

SECOND ionisation energy (Ei2): Energy required to remove SECOND OUTERMOST electron. M+ M2+ + 1e-

Inner level

Hard to remove close to nucleus

Second energy level

Outer (valence) level

Easy to remove far from the nucleus

This graph provides EVIDENCE for energy levels.

FIRST ionisation energy (Ei1): Energy required to remove OUTERMOST electron. M M+ + 1e-

First Ionisation Energies

Identify any trends or patterns in this graph.

What does this graph tell us about the electronic structure of the atom?

Patterns in EnergiesFIRST ionisation energy (Ei1): Energy required to remove OUTERMOST electron. M M+ + 1e-

Patterns in EnergiesFIRST ionisation energy (Ei1): Energy required to remove OUTERMOST electron. M M+ + 1e-

pss

FIRST ionisation energy (Ei1): Energy required to remove OUTERMOST electron. M M+ + 1e-

Patterns in First Ionization Energies (Ei1)

Patterns in First Ionization Energies (Ei1)PATTERN REASON

1 General decrease down a group

Atomic radius increases – outer shell is full so next e- is forced to enter a new energy level further from nucleus – less strongly attracted.

EVIDENCE FOR ENERGY LEVELS!!

2 General increase across a period

Increased nuclear charge – electrons in same energy level – MORE STRONGLY ATTRACTED by greater number of protons.

EVIDENCE OF – THE NUMBER OF e- IN EACH LEVEL

Patterns in First Ionization Energies (Ei1)PATTERN REASON

1 General decrease down a group

Atomic radius increases – e- further from nucleus – less strongly attracted.

2 General increase across a period

Increased nuclear charge – electrons in same energy level – MORE STRONGLY ATTRACTECD.

3 Third element’s Ei1 in a period is LOWER than second.

Outer electron in third element enters a NEW SUB LEVEL!

4 Sixth element’s Ei1 is LOWER than the fifth.

Outer element in sixth is PAIRED.

First Ionisation Energies

H

1 proton

1s

H’s electron would be removed.

Which of the following electrons would be easier to remove?

Bohr Orbits - energy levels

N = 4

N = 3

N = 2

N = 1

Electron StructureEnergy sub levels and orbitals

1s orbital

2s

2p orbitals3s

3p orbitals4s

4p (3d orbitals)

ANGLE 90O

Arrangement of the p-orbitals.

Pauli:– Electrons occupy _____

______________ levels.

– Max ____________ per orbital

– ______________ occurs when two electrons sharing the same orbital.

Electron distributionEnergy levels (1,2,3 etc) are divided up into ______________________ each of which has a specific number of orbitals

(s-___, p-____, d- ____).

N N=1 first energy level

N=2 second energy level

Pauli’s Exclusion Principle:– Electrons occupy lowest

vacant energy levels.

– Max two electrons per orbital

– spin paring occurs when two electrons sharing the same orbital.

Electron distributionEnergy levels (1,2,3 etc) are divided up into sub-levels (s, p, d, f) each of which has a specific number of orbitals

(s-1, p-3, d-5).

N

S N

S

N=1 first energy level

N=2 second energy level

Electron Structure Blanks

4s

3s

2s

1s

3p

2p

4s

3s

2s

1s

3p

2p

Electron Structure Afbau Diagrams

1s

4s

3s

2s

1s

3p

2p

H: 1s1He: 1s2

Electron Structure Afbau Diagrams

1s

4s

3s

2s

1s

3p

2p

H: 1s1He: 1s2

Hydrogen has only one electron so it would go into the first available orbital – the 1s orbital.

It takes less energy to spin pair than to move to a new energy level so Helium would have two electrons in the 1s orbital.

Protons 1 Protons 2

Electron Structure – Aufbau Diagrams

4s

3s

2s

1s

3p

2p

4s

3s

2s

1s

3p

2p

Li 1s2 2s1 Be 1s2 2s2

S, p, d notation

Electron Structure

4s

3s

2s

1s

3p

2p

4s

3s

2s

1s

3p

2p

B 1s2 2s2 2p1

C 1s2 2s2 2p2

Electron Structure

4s

3s

2s

1s

3p

2p

4s

3s

3p

N 1s2 2s2 2p3

O 1s2 2s2 2p4

2s

1s

2p

Electron Structure

4s

3s

2s

1s

3p

2p

4s

3s

2s

1s

3p

2p

F 1s2 2s2 2p5

Ne 1s2 2s2 2p6

Electron Structure

4s

3s

2s

1s

3p

2p

4s

3s

2s

1s

3p

2p

Na 1s2 2s2 2p6 3s1

Mg 1s2 2s2 2p6 3s2

Electron Structure

4s

3s

2s

1s

3p

2p

4s

3s

2s

1s

3p

2p

Al 1s2 2s2 2p6 3s2 3p1

Si 1s2 2s2 2p6 3s2 3p2

Electron Structure

4s

3s

2s

1s

3p

2p

4s

3s

2s

1s

3p

2p

P 1s2 2s2 2p6 3s2 3p3

-----------------------------

Cl 1s2 2s2 2p6 3s2 3p5

Ei Trends in a group

4s

3s

2s

1s

3p

2p

Li 1s2 2s1

4s

3s

2s

1s

3p

2p

Na 1s2 2s2 2p6 3s1

OUTER ELECTRON FURTHER FROM NUCLEUS – LESS ENERGY REQUIRED TO REMOVE IT – LOWER EI1

COMPLETE INNER LEVELS SHIELD THE OUTER ELECTRONS FROM THE EFFECTS OF THE INCREASED NUCLEAR CHARGE

3 PROTONS 11 PROTONS

FIRST Ei DECREASES DOWN A GROUP!

Electron Structure

4s

3s

2s

1s

3p

2p

4s

3s

2s

1s

3p

2p

B 1s2 2s2 2p1

C 1s2 2s2 2p2

Ei1 INCREASES

5 PROTONS6 PROTONS!

FIRST IONISATION ENERGY INCREASES FROM L R ACROSS A PERIODATOMIC RADIUS DECREASES BECAUSE ELECTRONS ARE MORE STRONGLY ATTRACTED BY THE INCREASED NUCLEAR CHARGE!!! MORE ENERGY REQUIRED TO REMOVE THE OUTER ELECTRON! GREATER FIRST IONIZATION ENERGY!!

Third IE lower than Second!

4s

3s

2s

1s

3p

2p

Be 1s2 2s2

4s

3s

2s

1s

3p

2p

B 1s2 2s2 2p1

3 protons 4 protons

New sublevel (p) slightly higher in energy – less strongly attracted – slightly less energy required to remove!

6th Ei lower than 5th!

4s

3s

2s

1s

3p

2p

4s

3s

2s

1s

3p

2p

N 1s2 2s2 2p3

O 1s2 2s2 2p4

6 PROTONS 7 PROTONS

Paired electrons – pairing requires energy – slightly higher energy state – less energy required to remove!