The Development of the Periodic Table

The Development of the Periodic Table

Chapter 7 Section 1Chapter 7 Section 1

Timeline of Development…

Timeline of Development…

1790’sAntoine Lavoisier: compiled a list

of elements (about 23)Mid-1800’s

Scientists developed a way to determine atomic mass

1870About 70 known elements

1790’sAntoine Lavoisier: compiled a list

of elements (about 23)Mid-1800’s

Scientists developed a way to determine atomic mass

1870About 70 known elements

Ah Ha!My life has

purpose again

OrganizationOrganization

Meyer, Mendeleev & MoseleyMendeleev gets most of the creditOrganized by atomic mass (just as

Newlands) but changed columnsOrganized into columns with similar

propertiesLeft blank spaces for places where

he thought elements should be, but weren’t discovered yet

Table 7.1?

Meyer, Mendeleev & MoseleyMendeleev gets most of the creditOrganized by atomic mass (just as

Newlands) but changed columnsOrganized into columns with similar

propertiesLeft blank spaces for places where

he thought elements should be, but weren’t discovered yet

Table 7.1?

Mendeleev’s PredictionsMendeleev’s Predictions

Why not atomic #?Why not atomic #?

It was found that some of Mendeleev’s elements were incorrectly placed

Why didn’t he use atomic number instead of atomic mass?

Answer: atomic #’s weren’t discovered until the early 1900’s

It was found that some of Mendeleev’s elements were incorrectly placed

Why didn’t he use atomic number instead of atomic mass?

Answer: atomic #’s weren’t discovered until the early 1900’s

Moseley’s AdaptationMoseley’s Adaptation

After Henry Moseley discovered protons (and atomic number) he changed the organization and fixed Mendeleev’s problems

Periodic Law:Periodic repetition of chemical and

physical properties of the elements when arranged by increasing atomic number

After Henry Moseley discovered protons (and atomic number) he changed the organization and fixed Mendeleev’s problems

Periodic Law:Periodic repetition of chemical and

physical properties of the elements when arranged by increasing atomic number

Parts of the Periodic TableParts of the Periodic TableColumns = Groups (or families)

Rows = Periods

Sections of the PTSections of the PT

Transition Elements

Inner Transition Elements

Other periodic tables…Other periodic tables…

Why?Why?

Why do things behave the way they do?The best predictor/explanation of why

elements react are found in:Their # of electronsThe way their electrons are organizedThe size of the atomsHow much they want electrons or how much

they want to get rid of electrons

Why do things behave the way they do?The best predictor/explanation of why

elements react are found in:Their # of electronsThe way their electrons are organizedThe size of the atomsHow much they want electrons or how much

they want to get rid of electrons

Valence ElectronsValence Electrons

Electrons in the outermost energy level of an atom

Core Electrons: all electrons that are not in the valence shell

Electrons in the outermost energy level of an atom

Core Electrons: all electrons that are not in the valence shell

Na1s22s22p63s1

Electron ShieldingElectron Shielding

Positives & Negatives are attracted to each other

Effective Nuclear Charge: describes the pull on the electrons by the nucleus

Zeff = Z - S

Positives & Negatives are attracted to each other

Effective Nuclear Charge: describes the pull on the electrons by the nucleus

Zeff = Z - SEffective Nuclear Charge

Shielding constant(# of non-valence electrons)

Nuclear Charge(# of protons)

Atomic SizeAtomic Size

50ml + 50ml = ?Atomic Size

Atoms of different elements have different sizes

What happens to Zeff as we go down a group?

As we go across a period?

50ml + 50ml = ?Atomic Size

Atoms of different elements have different sizes

What happens to Zeff as we go down a group?

As we go across a period?

Atomic RadiusAtomic Radius

What is it?What is it?

Atomic Radius TrendAtomic Radius Trend

Incre

ase

s

Increases

Atomic Radius TrendAtomic Radius Trend

Why?1) As you go down a group,

principle energy levels are added(n=1, n=2, n=3)

This increases the radius

Why?1) As you go down a group,

principle energy levels are added(n=1, n=2, n=3)

This increases the radius

Incre

ase

s

Increases

Atomic Radius TrendAtomic Radius Trend

Why?2) As you go across a period:

No energy levels are addedProtons are added

Why?2) As you go across a period:

No energy levels are addedProtons are added

Incre

ase

s

Increases

Ionic RadiusIonic Radius

Ions:An atom that has an overall positive

or negative chargeExamples:

Cl-1 (Chlorine with 17 protons and 18 electrons)

Mg2+ (Magnesium with 12 protons and 10 electrons)

What happens to size when atoms do this?

Ions:An atom that has an overall positive

or negative chargeExamples:

Cl-1 (Chlorine with 17 protons and 18 electrons)

Mg2+ (Magnesium with 12 protons and 10 electrons)

What happens to size when atoms do this?

PositiveNucleus

Ionic Radius TrendIonic Radius Trend

Positive Atoms To become positive, atoms lose

electronsWhat happens to size if you lose

electrons?Hint: You now have more positives

pulling in less negatives

Positive Atoms To become positive, atoms lose

electronsWhat happens to size if you lose

electrons?Hint: You now have more positives

pulling in less negatives

Ionic Radius TrendIonic Radius Trend

Negative AtomsTo become negative, atoms gain

electronsWhat happens to size if you gain

electrons?Hint: You now have more negatives

pulling out

Negative AtomsTo become negative, atoms gain

electronsWhat happens to size if you gain

electrons?Hint: You now have more negatives

pulling out PositiveNucleus

Chapter 7 Test Chapter 7 Test

Monday – January 7th

Development of the Periodic Table Periodic Trends (what & why)

Atomic radius Ionic radius Ionization energy Electron Affinity

Isoelectronic Ions Groups of the Periodic

Monday – January 7th

Development of the Periodic Table Periodic Trends (what & why)

Atomic radius Ionic radius Ionization energy Electron Affinity

Isoelectronic Ions Groups of the Periodic

Comparing Atomic SizeComparing Atomic Size

Remember isoelectronicWhen atoms have the same electron

configuration, which one is bigger?Example: a) Na+ b) F-1 c) O-2

O-2 > F-1 > Na+

Remember isoelectronicWhen atoms have the same electron

configuration, which one is bigger?Example: a) Na+ b) F-1 c) O-2

O-2 > F-1 > Na+

Radius decreases with increasing nuclear charge (# of protons)

Na = +11F = +9O = +8

Sample 7.6Sample 7.6

Ionization EnergyIonization Energy

The energy required to remove an electron from an atom

1st IE: Energy to remove the first electron

Na Na+ + e-

2nd IE: Energy to remove the 2nd

Na+ Na2+ + e-

3rd IE, 4th IE etc…

The energy required to remove an electron from an atom

1st IE: Energy to remove the first electron

Na Na+ + e-

2nd IE: Energy to remove the 2nd

Na+ Na2+ + e-

3rd IE, 4th IE etc…

Trend in 1st Ionization Energy

Trend in 1st Ionization Energy

Incr

ease

s

Increases

Hard to steal

electrons

Easy to steal

electrons

IE Equations & EnergiesIE Equations & Energies

We show the change through an equation:

Na Na+ + e- E=+495Na+ Na+2 + e- E= +4562Why is the 2nd IE so much bigger?

We show the change through an equation:

Na Na+ + e- E=+495Na+ Na+2 + e- E= +4562Why is the 2nd IE so much bigger?

Spikes in IESpikes in IE

Sample 7.7Sample 7.7

Electron AffinityElectron Affinity

The measure of how much an atom wants to gain an electron

For most atoms, energy is released when this happensDelta E = negative

The measure of how much an atom wants to gain an electron

For most atoms, energy is released when this happensDelta E = negative

Affinity vs IonizationAffinity vs Ionization

Ionization energyCl Cl+ + e- E = 1251 kJ/mol

Electron AffinityCl + e- Cl- E = -349 kJ/mol

Ionization energyCl Cl+ + e- E = 1251 kJ/mol

Electron AffinityCl + e- Cl- E = -349 kJ/mol

More negative = more energy given off = more

favorable

Electron AffinityElectron Affinity

Incr

ease

s

Increases

Fluorine has the most electron

affinity