atomicstructureoutcome7-8.ppt

(1)

Section 12.1

Classification of the Elements

 OBJECTIVES:OBJECTIVES:

• Use electron configurations to classify Use electron configurations to classify

elements as noble gases, representative

elements, transition metals, or inner

transition metals.

(2)

12.1 The Development of the Periodic Table

Dmitri Mendeleev took the 70 known elements and listed them in several columns based on their physical and chemical

properties. The main property he used was atomic mass, but this led to a periodic repetition of other properties, thus creating the first periodic table.

In 1913 Henry Moseley determined the nuclear

(3)

12.2 The Modern Periodic Table

The modern periodic table is arranged in 7 rows of

elements, with increasing atomic number, and 18 columns or families. The 7 horizontal rows are called periods.

The families are identified as 2 specific groups, A or B. The “A” group of elements are also known as representative

(4)

The sequence of charge is the same in all the periods and this led to the creation of the Periodic Law which states

that:

“When the elements are arranged in order of increasing atomic number, there is a periodic pattern in their physical

(5)

12.3 Electron Configuration and Periodicity

Of the 3 subatomic particles the electron plays the greatest role in the physical and chemical properties of the elements.

(6)

How to get the electron configuration of an element

The electron structure around an atom is based on the fact that in nature everything seeks the lowest possible energy because this is the most stable of states. In the world of the atom the electrons

(7)

The structure of an atoms electrons is based on location around an atom and the energy of the electrons in those locations

1) There are 7 main energy (quantum) levels around the

nucleus of an atom numbered 1 to 7

2) Within each quantum level there are anywhere from 1 to

4 sublevels labelled s, p, d and f

3) Within each sublevel there are could be 1, 3, 5 or 7

orbitals

(8)

Quantum energy level

Sublevel

orbital

- spin electron

+ spin electron

(9)

Three rules govern the electron configuration of an atom:

1) the Aufbau principle – Electrons enter the orbitals of lowest

energy(ground state) first.

2) The Pauli Exclusion Principle – Any orbital may contain at most 2

electrons, but they must be of opposite spin

(10)

Writing Electron Configurations

Order of Filling Sublevels with Electrons

(11)

or

(12)

(13)

1

1ss11

1s

1s2222ss11

1s

1s222s2s222p2p6633ss11

1s

1s222s2s222p2p663s3s223p3p6644ss11

1s

1s222s2s222p2p663s3s223p3p664s4s223d3d10104p4p6655ss11

1s

1s222s2s222p2p663s3s223p3p664s4s223d3d10104p4p665s5s224d4d10 10 5p5p6666ss11

1s

1s222s2s222p2p663s3s223p3p664s4s223d3d10104p4p665s5s224d4d10105p5p666s6s224f4f141455

d

d10106p6p6677ss11

(14)

He 2 Ne 10 Ar 18 Kr 36 Xe 54 Rn 86 1

1ss22

1s

1s222s2s222p2p66

1s

1s222s2s222p2p663s3s223p3p66

1s

1s222s2s222p2p663s3s223p3p664s4s223d3d10104p4p66

1s

1s222s2s222p2p663s3s223p3p664s4s223d3d10104p4p665s5s224d4d10105p5p66

1s

1s222s2s222p2p663s3s223p3p664s4s223d3d10104p4p665s5s224d4d10 10

5p

(15)

Elements can be classified into 4 categories based on their electron configuration.

1) The Noble Gases (inert gases which do not have any chemical reactivity) –

elements with outermost s and p sublevels which are full.

2) Representative Elements (columns 1,2,13-17) – elements that partially filled

outermost s and p sublevels

3) Transition Elements (all metals except columns 1 and 2) – elements whose

outermost s and nearby d sublevels contain electrons

(16)

Writing electron

configurations the easy

way

Yes there is a shorthand

(17)

Electron Configurations repeat

 The shape of the periodic table is a The shape of the periodic table is a representation of this repetition.

representation of this repetition.

 When we get to the end of the column When we get to the end of the column the outermost energy level is full.

(18)

The Shorthand

 Write symbol of the noble gas before Write symbol of the noble gas before the element, in [ ].

the element, in [ ].

 Then, the rest of the electrons.Then, the rest of the electrons.  Aluminum’s full configuration:Aluminum’s full configuration:

1s1s222s2s222p2p663s3s223p3p11

(19)

More examples

 Ge = Ge = 1s1s222s2s222p2p663s3s223p3p664s4s223d3d10104p4p22

• Thus, Ge = Thus, Ge = [Ar] 4s[Ar] 4s223d3d10104p4p22

 Hf = Hf = 1s1s222s2s222p2p663s3s223p3p664s4s223d3d10104p4p665s5s2 2 4d

4d10105p5p666s6s224f4f14145d5d22

(20)

The Shorthand Again

Sn- 50 electrons The noble gas before it is Kr

[ Kr ] Takes care of 36

Next 5s2

5s2 Then 4d10

4d10 Finally 5p2

(21)

Assignment

 Objective Ws 1- 6Objective Ws 1- 6

(22)

Section 12.2

Periodic Trends

 OBJECTIVES:OBJECTIVES:

• Interpret Interpret group trendsgroup trends in atomic radii, ionic in atomic radii, ionic radii, ionization energies, and

radii, ionization energies, and

electronegativities.

(23)

Section 12.2

Periodic Trends

 OBJECTIVES:OBJECTIVES:

• Interpret Interpret period trendsperiod trends in atomic radii, in atomic radii, ionic radii, ionization energies, and

ionic radii, ionization energies, and

electronegativities.

(24)

Trends in Atomic Size

 First problem: Where do you start First problem: Where do you start measuring from?

measuring from?

 The electron cloud doesn’t have a The electron cloud doesn’t have a definite edge.

definite edge.

 They get around this by measuring They get around this by measuring more than 1 atom at a time.

(25)

Atomic Size

Atomic Radius = half the distance between two Atomic Radius = half the distance between two

nuclei of a diatomic molecule.

}

(26)

Trends in Atomic Size

 Influenced by three factors:Influenced by three factors: 1. Energy Level

1. Energy Level

• Higher energy level is further away.Higher energy level is further away.

2. Charge on nucleus

• More charge pulls electrons in closer.More charge pulls electrons in closer.

 3. Shielding effect3. Shielding effect

(27)

Group trends

 As we go down a As we go down a group...

group...

 each atom has each atom has another energy another energy

level, level,

(28)

Periodic Trends

 As you go across a period, the radius gets As you go across a period, the radius gets

smaller.

 Electrons are in Electrons are in same energy levelsame energy level..  More More nuclear chargenuclear charge..

 Outermost electrons are closer.Outermost electrons are closer.

(29)

(30)

Trends in Ionization Energy

 The amount of energy required to The amount of energy required to

completely remove an electron from a completely remove an electron from a

gaseous atom. gaseous atom.

 Removing one electron makes a 1+ ion.Removing one electron makes a 1+ ion.  The energy required to remove the first The energy required to remove the first

electron is called the

electron is called the first_first ionization _ionization energy.

(31)

Ionization Energy

 TheThe second second ionization energy is the ionization energy is the

energy required to remove the second energy required to remove the second

electron. electron.

 Always greater than first IE.Always greater than first IE.

 The The thirdthird IE is the energy required to IE is the energy required to remove a third electron.

remove a third electron.

(32)

Symbol First Second Third HH eLi Be BC NO F Ne 1312 2731

520 900

800 1086 1402 1314 1681 2080 5247 7297 1757 2430 2352 2857 3391 3375 3963 11810 14840 3569 4619 4577 5301 6045 6276

Ionization Energies Table 12.1, p. 281 kJ/mol

Ion Formed

Be 2+

(33)

What determines IE

 The greater the nuclear charge, the greater The greater the nuclear charge, the greater

IE.

 Greater distance from nucleus decreases IEGreater distance from nucleus decreases IE

 Filled and half-filled orbitals have lower Filled and half-filled orbitals have lower

energy, so achieving them is easier, lower

IE.

(34)

Shielding

 The The electronelectron on the on the

outermost energy level

has to look through all

the other energy levels to

see the nucleus.

 SecondSecond electronelectron has same has same

shielding, if it is in the

same period

(35)

Group trends

 As you go down a group, first IE As you go down a group, first IE decreases because...

decreases because...

(36)

Periodic trends

 All the atoms in the same period have All the atoms in the same period have the same energy level.

the same energy level.  Same shielding.Same shielding.

 But, increasing nuclear chargeBut, increasing nuclear charge

 So IE generally increases from left to So IE generally increases from left to right.

right.

(37)

F irs t I on iz at io n en er gy Atomic number He

 He has a greater IE He has a greater IE than H.

than H.

 same shielding same shielding  greater nuclear greater nuclear

charge charge

(38)

F irs t I on iz at io n en er gy Atomic number H He Li Be B C N O F Ne

 Na has a lower IE

than Li

 Both are s1

 Na has more

shielding

 Greater distance

(39)

F

irs

t I

on

iz

at

io

n

en

er

gy

Atomic number

H to Br

(40)

Driving Force

 Full Energy Levels require lots of energy Full Energy Levels require lots of energy to remove their electrons.

to remove their electrons.

 Noble Gases have full orbitals.Noble Gases have full orbitals.

 Atoms behave in ways to achieve noble Atoms behave in ways to achieve noble gas configuration.

(41)

2nd Ionization Energy

 For elements that reach a filled or half-For elements that reach a filled or half-filled orbital by removing 2 electrons, filled orbital by removing 2 electrons,

2nd IE is lower than expected. 2nd IE is lower than expected.  True for sTrue for s2 2

(42)

3rd IE

 Using the same logic sUsing the same logic s22pp11 atoms have an atoms have an low 3rd IE.

low 3rd IE.

 Atoms in the aluminum family form 3+ Atoms in the aluminum family form 3+ ions.

ions.

 2nd IE and 3rd IE are always higher 2nd IE and 3rd IE are always higher than 1st IE!!!

(43)

(44)

Trends in Electron Affinity

 The energy change associated with The energy change associated with addingadding

an electron

an electron to a gaseous atom. to a gaseous atom.

 Easiest to add to group 7A.Easiest to add to group 7A.

 Gets them to full energy level.Gets them to full energy level.

 Increase from left to right: atoms become Increase from left to right: atoms become

smaller, with greater nuclear charge.

(45)

(46)

Trends in Ionic Size

 Cations form by Cations form by losinglosing electrons. electrons.

 Cations are smaller than the atom they Cations are smaller than the atom they come from.

come from.

 Metals form cations.Metals form cations.

 Cations of representative elements have Cations of representative elements have noble gas configuration.

(47)

(48)

Ionic size

 Anions form by Anions form by gaininggaining electrons. electrons.

 Anions are bigger that the atom they Anions are bigger that the atom they come from.

come from.

 Nonmetals form anions.Nonmetals form anions.

 Anions of representative elements have Anions of representative elements have noble gas configuration.

(49)

(50)

Configuration of Ions

 Ions always have noble gas configuration.Ions always have noble gas configuration.

 Na is: 1sNa is: 1s222s2s222p2p663s3s11

 Forms a 1+ ion: 1sForms a 1+ ion: 1s222s2s222p2p66

 Same configuration as neon.Same configuration as neon.

 Metals form ions with the configuration of Metals form ions with the configuration of

the noble gas before them - they lose

electrons.

(51)

Configuration of Ions

 Non-metals form ions by gaining Non-metals form ions by gaining electrons to achieve noble gas

electrons to achieve noble gas configuration.

configuration.

 They end up with the configuration of They end up with the configuration of the noble gas after them.

(52)

Group trends

 Adding energy levelAdding energy level

 Ions get bigger as you Ions get bigger as you

go down.

Li1+ Na1+

K1+

Rb1+

(53)

Periodic Trends

 Across the period, nuclear charge increases Across the period, nuclear charge increases

so they get smaller.

 Energy level changes between anions and Energy level changes between anions and

cations.

Li1+

Be2+

B3+

C4+

N

(54)

1-Size of Isoelectronic ions

Size of Isoelectronic ions

 Iso- means the sameIso- means the same

 Iso electronic ions have the same # of Iso electronic ions have the same # of electrons

electrons

 AlAl3+3+ Mg Mg2+ 2+ NaNa1+ 1+ Ne FNe F1- 1- OO2- 2- and Nand N3- 3- all have 10 electronsall have 10 electrons

(55)

Size of Isoelectronic ions

 Positive ions that have more protons Positive ions that have more protons would be smaller.

would be smaller.

Al3+

Mg2+

Na1+ Ne F

1- O2- N

(56)

3-Electronegativity

Electronegativity

 The tendency for an atom to The tendency for an atom to attract attract

electrons to itself when it is

electrons to itself when it is chemically chemically combined

combined with another element.with another element.

 How fair is the sharing?How fair is the sharing?

 Big electronegativity means it pulls the Big electronegativity means it pulls the

electron toward it.

 Atoms with large negative electron affinity Atoms with large negative electron affinity

have larger electronegativity.

(57)

(58)

Group Trend

 The further down a group, the farther The further down a group, the farther the electron is away, and the more

the electron is away, and the more electrons an atom has.

(59)

Periodic Trend

 Metals are at the left of the table.Metals are at the left of the table.

 They let their electrons go easilyThey let their electrons go easily

 Low electronegativityLow electronegativity

 At the right end are the nonmetals.At the right end are the nonmetals.

 They want more electrons.They want more electrons.

 Try to take them away from othersTry to take them away from others

(60)

(61)

(62)

Group IA - The Alkali Metals (Li, Na, K, Rb, Cs, Fr)

Highly

(63)

Group IIA - The Alkaline Earth Metals

(Be, Mg, Ca, Sr, Ba, Ra)

Lose 2 valence electrons

Also react with H₂O to form an

alkaline solution (basic), and hydrogen gas, but less violently

Ca_(s) + 2H₂O_(l) _

(64)

Group IIA - The Alkaline Earth Metals

(65)

Group IIA - The Alkaline Earth Metals

flashbulbs

Strong reaction of magnesium with oxygen to produce magnesium

oxide

(66)

Group IIIA - The Boron Family

(B, Al, Ga, In, Tl)

Boron is mined in the form of

Borax, and is used in laundry soap

Laboratory glassware contains

(67)

Group IIIA - The Boron Family

(B, Al, Ga, In, Tl)

(68)

Group IIIA - The Boron Family

(B, Al, Ga, In, Tl)

Gallium Arsenide is used in the

(69)

Group IVA - The Carbon Family

(C, Si, Ge, Sn, Pb)

Carbon is essential for life

(70)

Group IVA - The Carbon Family

(C, Si, Ge, Sn, Pb)

Carbon is found in different structures or

(71)

Group IVA - The Carbon Family

(C, Si, Ge, Sn, Pb)

Quartz or SiO₂

(72)

Group VA - The Nitrogen Family

(N, P, As, Sb, Bi)

There are two

(73)

Group VIA - The Oxygen Family

(O, S, Se, Te, Po)

Stratospheric ozone shields us from harmful UV radiation. Ozone is destroyed by Cl-containing molecules used in

refrigeration

(74)

Group VIIA - The Halogens (F, Cl, Br, I, At)

(75)

Group VIIIA - The Noble (Inert) Gases

He, Ne, Ar, Kr, Xe

(76)

The Transition Elements

(77)

References

This power point presentation was

created by Terry Sproat used with

permision