chem 2010_3 periodic trends

8/11/2019 Chem 2010_3 Periodic Trends

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PeriodicTrends


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Periodic Trends

Moving across the Periodic Table from leftto right, the elements

chemical and physical properties change from those of metalsto those

of metalloids(or semi-metals) and finally to those of non-metals:

Metals Metalloids Non-metals

Magnesium Silicon Sulphur


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Periodic Trends

Question:What are the typical chemical and physical properties of metals?

Good conductors of heat and electricity.

Tend to have high melting points and boiling points.

Tend to be hard and strong.

Tend to have a high density.

Have a metallic lustre (are shiny).

Malleable and ductile (shape can be changed without breaking). Sonorous (ring when struck).

React by losing their valence electrons.

Oxides are basic.


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Periodic Trends

Question:What are the typical chemical and physical properties of

non-metals?

Poor conductors of heat and electricity (insulators).

Tend to have low melting points and boiling points.

Tend to be soft.

Tend to have a low density.

Surface is dull (unless crystalline). Tend to be brittle.

Not sonorous.

React by gaining valence electrons.

Oxides are acidic.


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Periodic Trends

Question:

What are the typical chemical and physical properties of

metalloids?

Semiconductors (electrical conductivity varies greatly dependingupon the conditions that they are subject to).

Oxides are amphoteric (oxides can be either acidic or basicdepending upon the conditions that they are subject to).


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1 2 Group 3 4 5 6 7 0

1 H He

2 Li Be B C N O F Ne

3 Na Mg Al Si P S Cl Ar

4 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr

5Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe

6 Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn

7 Fr Ra Ac

Period

Periodic Trends

The dividing linebetween metals (left)and non-metals (right).


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1 2 Group 3 4 5 6 7 0

1 H He






7 Fr Ra Ac

Period

Periodic Trends Metals!


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1 2 Group 3 4 5 6 7 0

1 H He






7 Fr Ra Ac

Period

Periodic Trends Metalloids!


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1 2 Group 3 4 5 6 7 0

1 H He






7 Fr Ra Ac

Period

Periodic Trends Non-metals!


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1 2 Group 3 4 5 6 7 0

1 H He




5 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe


7 Fr Ra Ac

Period

Periodic Trends Summary!


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Periodic Trends

Question:

Lithium and sodium are both elements from Group 1 of the Periodic

Table.

Draw the electron configurations of lithium (atomic number = 3) andsodium (atomic number = 11):


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Periodic Trends

Question:

What do the electron configurations of the Group 1 metals have in

common?


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Periodic Trends

Answer:

The Group 1 metals all have 1 electron in their valence shell.


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Periodic Trends

Question:How do the Group 1 metals react to obtain a complete valence

shell?


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Periodic Trends

Answer:The Group 1 metals all react by losing their single valence electron to

form an ion with a complete valence shell and a single positive

charge. Because the Group 1 metals all react in this way, they are

said to have similar chemical properties.


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Periodic Trends

Question:Sodium (symbol Na) and caesium (symbol Cs) are both in

Group 1 of the Periodic Table.

The formula of sodium chloride is NaCl. The formula of sodium

carbonate is Na2CO3. The formula of sodium sulphate is Na2SO4.Using this information, predict the formulae of caesium chloride,

caesium carbonateand caesium sulphate.

Answer:Caesium chloride CsCl.

Caesium carbonate Cs2CO3.

Caesium sulphate Cs2SO4.


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Periodic Trends

Question:Some information about the Group 1 metals is given in the table

below:

Element Melting Point / C Metallic Radius / nm

Lithium Li 180.0 0.152

Sodium Na 97.8 0.186

Potassium K ? ?

Rubidium Rb 38.9 0.244

Caesium Cs 28.7 0.262

Predict the melting point and metallic radius of potassium.


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Periodic Trends

Answer:Some information about the Group 1 metals is given in the table

below:

Element Melting Point / C Metallic Radius / nm

Lithium Li 180.0 0.152

Sodium Na 97.8 0.186

Potassium K 63.7 0.231

Rubidium Rb 38.9 0.244

Caesium Cs 28.7 0.262


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Periodic Trends

Question:Fluorine and chlorine are both elements from Group 7 of the

Periodic Table.

Draw the electron configurations of fluorine (atomic number = 9)and chlorine (atomic number = 17):


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Periodic Trends

Question:What do the electron configurations of the Group 7 elements have

in common?


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Periodic Trends

Answer:The Group 7 elements all have 7 electrons in their valence shell.


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Periodic Trends

Question:How do the Group 7 elements react to obtain a complete valence

shell?


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Periodic Trends

Answer:The Group 7 elements all react by gaining a single valence electron to

form an ion with a complete valence shell and a single negative

charge. Because the Group 7 elements all react in this way, they are

said to have similar chemical properties.


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Periodic Trends

Question:Chlorine (symbol Cl) and astatine (symbol At) are both in

Group 7 of the Periodic Table.

The formula of sodium chloride is NaCl. The formula of magnesium

chloride is MgCl2. The formula of aluminium chloride isAlCl3. Usingthis information, predict the formulae of sodium astatide,

magnesium astatideand aluminium astatide.

Answer:Sodium astatide NaAt.

Magnesium astatide MgAt2.

Aluminium astatideAlAt3.


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Periodic Trends

Question:Some information about the Group 7 elements is given in the table

below:

Element Melting Point / C Covalent Radius / nm

Fluorine F 220 0.072

Chlorine Cl ? ?

Bromine Br 7.2 0.114

Iodine I 114 0.133

Astatine At 302 0.140

Predict the melting point and covalent radius of chlorine.


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Periodic Trends

Answer:Some information about the Group 7 elements is given in the table

below:

Element Melting Point / C Covalent Radius / nm

Fluorine F 220 0.072

Chlorine Cl 101 0.099

Bromine Br 7.2 0.114

Iodine I 114 0.133

Astatine At 302 0.140


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Periodic Trends

Question:Elements in the same Group of the Periodic Table have similar

chemical properties because they lose or gain the same number of

electrons to fill their valence shells. In what way do the elements in

the same Group of the Periodic Table differfrom each other?

Answer:The reactivityof the elements in the same Group varies. On

descending a Group of metals, the elements become more reactive.

On descending a Group of non-metals, the elements become less

reactive. In addition, the physical propertiesof the elements in the

same Group varies. On descending a Group of metals, their melting

points tends to decrease. On descending a Group of non-metals,

their melting points tends to increase.


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Periodic Trends

Question:Sodium and chlorine are both in the same Period of the

Periodic Table. Draw the electron configurations of sodium

(atomic number = 11) and chlorine (atomic number = 17) and

state in what way their electron configurations are similar to

each other.


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Periodic Trends

Answer:Sodium and chlorine are both in the thirdPeriod of the Periodic Table

and so both atoms have threeelectron shells:


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Periodic Trends

Question:Complete the table below to show how the properties of the elements

changes across the Periodic Table:

Group 1 2 3 4 5 6 7 0

Element Na Mg Al Si P S Cl Ar

Metal / Non-metal

Number of

Valence

Electrons

Number of

Electrons Lost /

Gained

Charge on Ion

Valency


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Periodic Trends

Question:Complete the table below to show how the properties of the elements

changes across the Periodic Table:

Group 1 2 3 4 5 6 7 0

Element Na Mg Al Si P S Cl Ar

Metal / Non-metal Metal Metal MetalSemi-

metal

Non-

metal

Non-

metal

Non-

metal

Non-

metal

Number of

Valence

Electrons

1 2 3 4 5 6 7 8

Number of

Electrons Lost /

Gained

1 Lost 2 Lost 3 Lost4

Gained

3

Gained

2

Gained

1

Gained

0 Lost

or

Gained

Charge on Ion +1 +2 +3 4 3 2 1 0

Valency 1 2 3 4 3 2 1 0


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Periodic Trends

Summary: Moving across the Periodic Table from leftto right, the elements

chemical and physical properties change from those of metalsto

those of metalloidsand finally to those of non-metals.

Elements in the same Grouphave the same number of valenceelectrons and therefore have similarchemical properties.

Elements from the same Groupform compounds with the same

formulae.

On descendinga Group of elements, there is a gradual change in

their chemical and physical properties. Metalsbecome morereactiveand their melting points decrease. Non-metalsbecome less

reactiveand their melting points increase.

Elements in the same Periodhave the same number of electron

shells.


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Periodic Trends

Enrichment:

Consider the elements of the third Period, sodium to chlorine.

How does the size (atomic radius) of an atom vary from leftto right across the Periodic Table?

How does the ease with which an atom loses an electronfrom its valence shell (first ionization energy) vary from left toright across the Periodic Table?

Clueconsider how atomic number changer across thePeriodic Table from sodium to chlorine. Remember what theatomic number of an element represents.


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Periodic Trends

Symbolof

Element

Na Mg Al Si P S Cl

Atomic

Number11 12 13 14 15 16 17

Atomic

Radius /

nm

0.157 0.136 0.125 0.117 0.110 0.104 0.099

First

Ionization

Energy /

kJ mol-1

494 736 577 786 1060 1000 1260


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Periodic Trends

Symbolof

Element

Na Mg Al Si P S Cl

Atomic

Number

Number of protons within the nucleus of the atom increases.

Positive charge within the nucleus of the atom increases.

Force of attraction between the positive nucleus and negative electrons orbitingthe nucleus increases.

Atomic

Radius /

nm

0.157 0.136 0.125 0.117 0.110 0.104 0.099

First

Ionization

Energy /

kJ mol-1

494 736 577 786 1060 1000 1260


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Periodic Trends

As the force of attraction between the positive nucleus and

negative electrons that are orbiting the nucleus increases, the

electrons are pulled in closer to the nucleus and the size of

the atom (atomic radius) decreases.

As the force of attraction between the positive nucleus and

negative electrons that are orbiting the nucleus increases, theamount of energy required to remove an electron from the

valence shell of an atom (first ionization energy) increases.


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Periodic Trends

A Note on First Ionization Energy

The ease with which an atom of a particular elementloses a single electron from its valence shell is given byits first ionization energy. This is the energy required to

convert one mole of gaseous atoms to one mole ofgaseous ions, each with a single positive charge. It canbe summarised by the following equation:

E(g)

E+(g)

+ e

chem 2010_3 periodic trends

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