chuongtrinh chuong 8 9 group ia iia ok

7/28/2019 ChuongTrinh Chuong 8 9 Group IA IIA OK

http://slidepdf.com/reader/full/chuongtrinh-chuong-8-9-group-ia-iia-ok 1/69

THE S -BLOCK ELEMENTS



Introduction Modern chemical knowledge is based largely on principles

that answer the “why” as well as the “how-to.”

In the remaining chapters, we will emphasize facts and

applications, but we will refer to underlying principles

repeatedly.

Four of the 14 elements that comprise the s -block elements

are somewhat unusual cases, although not all for the same

reason.

Hydrogen is the simplest element, with one proton and oneelectron, and its behavior is rather special.

Helium lies in the s -block but its electron configuration fits with the

noble gases, and it will be considered in the next chapter.

Francium and radium are highly radioactive and we will not

consider them further.



GROUP IA: THE ALKALI METALS



Spodumene LiAl(SiO3)2



The Alkali Metals

Discoveries are recent.

Sodium and potassium (1807) by

electrolysis.

Cesium (1860) and rubidium (1861) from

emission spectra.

Francium (1939) from actinium

radioactive decay.

Most salts are water soluble.

Natural brines are good sources.

Natural deposits allow mining of solids.



FlameColors



Properties and Trends in Group 1A

The Group 1A metals exhibit regular trends for a

number of properties.

Irregular trends suggest that factors are working

against each other in determining a property (such as

the density ―discrepancy‖ between sodium andpotassium).

The alkali metals have two notable physical

properties: they are all soft and have low melting

points. When freshly cut, the alkali metals are bright and

shiny—typical metallic properties. The metals quickly

tarnish, however, as they react with oxygen in the air.



Diagonal Relationships:The Special Case of Lithium

In some of its properties, lithium and its

compounds resemble magnesium and itscompounds.

Lithium carbonate, fluoride, hydroxide, andphosphate are much less water soluble than those

of other alkali metals.

Lithium is the only alkali metal that forms a nitride(Li3N).

When it burns in air, lithium forms a normal oxide(Li2O) rather than a peroxide or a superoxide.

Lithium carbonate and lithium hydroxidedecompose to form the oxide on heating, while the

carbonates and hydroxides of other Group 1Ametals are thermally stable.



Diagonal

Relationships

The elements in

each encircled

pair haveseveral similar

properties.



Occurrence, Preparation, Use, & Reactions of the Alkali Metals

Sodium and potassium are isolated primarily from

brines (solutions of NaCl and KCl).

Lithium is obtained mostly from the mineral

spodumene, LiAl(SiO3)2.

To convert an alkali metal ion into an alkali metal

atom, the ion must take on an electron—a process of

reduction.

This is not easy with the alkali metals; they are

excellent reducing agents.

Potassium was the first alkali metal to be prepared by

electrolysis.



Liquid sodium is used as a heat transfer medium in some

types of nuclear reactors and in automobile engine valves,and its vapor is used in lamps for outdoor lighting.

Potassium is used in making KO2, used as an oxygen

source for miner’s “self -rescuers” and similar devices:

Lithium is used in lightweight batteries of the type

found in heart pacemakers, cellular telephones,

digital cameras, and portable computers.

Occurrence, Preparation, Use, & Reactions of the Alkali Metals

2 2 2 2 2 3 2 3 22 2 2 Na O KO CO Na CO K CO O



Group I Compounds

Halides

NaCl 50 milliontons/year in U.S.

Preservative, used

on roads, water

softener regeneration,feedstock for other chemicals

KCl from natural brines.

Plant fertilizers, feedstock.



I C d f



Important Compounds of

Lithium, Sodium, and Potassium

Lithium carbonate is the usual starting material for

making other lithium compounds:

Li2CO3(aq) + Ca(OH)2(aq) CaCO3(s) + 2 LiOH(aq)

One use of LiOH is to remove CO2 from expired air insubmarines and space vehicles:

2 LiOH(s) + CO2(g) Li2CO3(aq) + H2O

NaCl is the most important industrial sodium

compound (50 million tons/yr).

It is used to prepare a number of other chemicals and

consumer products, including plastics, paper, bleach,

soap, and laundry detergent.



Carbonates

Li2CO3 is unstable relative to the oxide.Used to treat manic depression (1-2 g/day).

Na2CO3 primarily used to manufacture

glass.

Currently mined from rich U.S. resources but

can be manufactured by the Solvay process

(E. So lvay, Belg ium , 1838-1922) .



Production and Use

2 NaCl(l) → 2 Na(l) + Cl2(g)

Electrolysis:

KCl(l) + Na(l) → 2 NaCl(l) + K(g)

Sodium as a reducing agent:

TiCl4 + 4 Na → Ti + 4 NaCl



Preparation of Sodium

Compounds from NaCl

The methods of preparation suggested by this diagram are not

necessarily the preferred industrial methods.



The Solvay Process—One Way

to Diagram an Industrial Process



The Alkali Metals and Living Matter

Hydrogen, oxygen, carbon, and nitrogen are the most

abundant elements in the human body, in the order listed.

Sodium and potassium ions are in a second tier of seven elements that account for about 0.9% of theatoms.

Sodium ions are found primarily in fluids outside cellsand potassium ions are abundant in fluids within cells.

Because most alkali metal compounds are water soluble, many drugs that are weak acids areadministered in the form of their sodium or potassiumsalts.

Lithium carbonate is used in medicine to level out thedangerous manic ―highs‖ that occur in manic-

depressive psychoses.



Sodium Sulfate

H2SO4(conc. aq) + NaCl(s) → NaHSO4(s) + HCl(g)

NaHSO4(s) + NaCl(s) → Na2SO4(s) + HCl(g)

I n the Kraft Process for making paper:

Na2SO4(s) + 4 C(s) → Na2S(s) + 4 CO(g)

45 kg/ton paper



Oxides and Hydroxides

Reaction with oxygen produces severalionic oxides.

In limited oxygen supplies:

M2O (small amounts of Li2O2 from Li). In excess oxygen:

Li and Na form the peroxide, M2O2.

K, Rb and Cs form the superoxide MO2.



Soaps and Detergents

A soap acts by dispersing grease and oil filmsinto microscopic droplets.

The droplets detach themselves from the

surfaces being cleaned, become suspended inwater, and are removed by rinsing.

The alkali metal soaps are water soluble; thealkaline earth metal soaps are not.

A soap can function well in hard water only after a part of it is used up to precipitate all thealkaline earth metal ions present; in other

words, the soap softens the water first.

D t t d S



Detergents and Soaps



Cleaning Action of a SoapA soap has a

hydrocarbon

“tail” …

… and an

ionic “head”

An oil droplet is

attracted to the

hydrocarbon tails, and

the ionic ends permit

the droplet to be

solubilized in water.



GROUP 2 THE ALKALINE EARTH METALS



GROUP 2: THE ALKALINE EARTH METALS

Emerald is based on

the mineral beryl:

3BeO·Al2O3 ·6SiO2



Principle forms:

carbonates, sulfates and silicates

Oxides and hydroxides only sparingly

soluble.

Basic or ―alkaline‖

Compounds do not decompose on

heating.

Therefore named ―earths‖

Heavier elements compounds are more

reactive and are similar to Group I (also in

other respects).

P i d T d i G 2A



Properties and Trends in Group 2A Group 2A shows the same general trends of

increasing atomic and ionic sizes and decreasing

ionization energies from top to bottom as doesgroup 1A.

The higher densities of the group 2A metals are

mainly a consequence of the large differences in

atomic sizes. The group 2A metals are all good reducing agents.

Mg(OH)2 is virtually insoluble in water, however …

As the cation size increases from top to bottom on

the periodic table, interionic attractions decrease instrength and the solubilities of the compounds in

water increase.

Ba(OH)2 is sufficiently soluble to be used as a titrant

in acid –base titrations.

ĐẶC ĐIỂM CHUNG



ĐẶC ĐIỂM CHUNG 1. Là kim loại hoạt động, tăng dần từ BeRa.

Kém so với KL kiềm do Z lớn, r nhỏ hơn 2. Dễ mất 2e trở thành M2+ trong hợp chất và

trong dung dịch

3. Thế điện cực tương đương KL kiềm

4. Thể hơi chỉ bao gồm phân tử 1 nguyên tử

5. Ion không màu; nhiều hợp chất ít tan

6. Be khác nhiều hơn so với Li và các

nguyên tố trong nhóm; Be giống nhiều Al,

Mg giống nhiều Zn



These were named alkaline earths because of their



. These were named alkaline earths because of their

intermediate nature between the alkalis (ox ides o f

the alkal i metals) and the rare earths (ox ides o f rare

earth m etals). The alkaline earth metals are si lvery co lored, so ft , low -

densi ty m etals , which react readi ly w ith halogens to

form ionic sal ts , and with water , though not as

rapidly as the alkali metals, to form strongly alkal ine

(basic) hyd rox ides . For example, where sodium and

potassium react with water at room temperature,

magnesium reacts only with steam and calcium with

hot water.

Mg + 2H2O → Mg(OH)2 + H2

Beryllium is an exception: It does not react with water or

steam, and its halides are covalent.

R ti f G 2A M t l



Reactions of Group 2A Metals Reactivity with water increases from beryllium to

barium: Beryllium does not react with water.

Magnesium reacts with steam but not with cold water.

Calcium reacts slowly with cold water.

Strontium and barium react more rapidly with cold water.

All the alkaline earth metals react with dilute acids to

displace hydrogen:

M(s) + 2 H+

(aq) M2+

(aq) + H2(g). The alkaline earth metals react with the halogens to

form the corresponding halides, with oxygen to form

the oxides, and with nitrogen to form the nitrides.

B lli



Beryllium

Unreactive toward air and water.

BeO does not react with water, all others

from hydroxides.

Be and BeO dissolve in strongly basicsolutions to form the BeO22- ion (therefore

are acidic ).

BeCl2

and BeF2

melts are poor

conductors:

Therefore they are covalent rather than ionic

solids.



The Special Case of Beryllium

• Beryllium is somewhat different from the rest of group 2A.• BeO does not react with water, while the other group 2A

metal oxides do so: MO + H2O M(OH)2.

• Be and BeO dissolve in strongly basic solutions to form

the BeO22 – ion. The oxide BeO has acidic properties. The

other alkaline earth metal oxides are basic.

• Molten BeF2 and BeCl2 are poor conductors of electricity;

they are molecular substances (see below). The other

group IIA compounds are almost entirely ionic.

B lli Chl id



Beryllium Chloride



Important Compounds of Magnesium and Calcium

Several magnesium compounds occur

naturally, either in mineral form or in brines.

These include the carbonate, chloride,

hydroxide, and sulfate.

Limestone is a naturally occurring form of

calcium carbonate, containing clay and other

impurities.

Portland cement is made by heating limestone,

clay, and sand. When the cement is mixed with

sand, gravel, and water, it solidifies into

concrete.





Magnesium and Calcium (cont’d)

Limestone is used in the metallurgy of iron andsteel to produce an easily liquefied mixture of

calcium silicates called slag, which carries away

impurities from the molten metal.

Precipitated (purified) calcium carbonate is usedextensively as a filler in paint, plastics, printing

inks, and rubber.

It is also used as a mild abrasive in toothpastes,food, cosmetics, and antacids.

Added to paper, calcium carbonate makes the

paper bright, opaque, smooth, and capable of

absorbing ink well.





Magnesium and Calcium (cont’d)

Quicklime (CaO) and slaked lime [Ca(OH)2] are thecheapest and most widely used bases, and are

usually the first choice for neutralizing unwanted acids.

Slaked lime sees extensive agricultural use.

Quicklime is used to neutralize sulfur oxides formed

when coal burns.

Gypsum has the formula CaSO4·2 H2O. Another

hydrate of calcium sulfate is plaster of paris which hasthe formula CaSO4 ·½ H2O and is obtained by heating

gypsum.

Gypsum is used to make the familiar ―drywall‖ or

―plaster board‖ wall material.



D iti f C CO (li )



Decomposition of CaCO3 (lime)

CaO + H2O → Ca(OH)2

slaked lime

In the lime slaker:

CaCO3 → CaO + CO2

burnt lime

or

quicklime

In the lime kiln:

Δ

Stalactites and Stalagmites



Stalactites and Stalagmites

CO2 + H2O → H3O+ + HCO3

-

K a = 4.410-7

HCO3- + H2O → H3O

+ + CO32-

K a = 4.710-11

CaCO3(s) + H2O(l) + CO2(g) → Ca(HCO3)2(aq)

Oth C d



Other Compounds

Gypsum, CaSO4·2H2O: Plaster of paris CaSO4·½H2O by heating

bypsum.

Used in drywall. BaSO4 used in X-ray imaging .

Slaked lime used in mortar:

CaO absorbs water from the cement to formCa(OH)2 which subsequently reacts with CO2

to form CaCO3.

Occurrence Preparation Uses and



Occurrence, Preparation, Uses, and

Reactions of Group 2A Metals

Calcium and magnesium rank just ahead of sodiumand potassium in abundance in the Earth’s crust.

Limestone is mainly CaCO3; dolomite is MgCO3·

CaCO3. Barium and strontium are found in the Earth’s crust at

about 400 ppm, and beryllium is found at 2 ppm.

An important mineral source of beryllium is the mineralberyl , Be3 Al2Si6O18.

Some familiar gemstones, including aquamarine and

emerald, are beryl, distinctively colored by impurities.

To obtain beryllium metal, beryl is first converted to



y y

BeF2. Then the BeF2 is reduced to beryllium, using

magnesium as the reducing agent.

Calcium is generally obtained by electrolysis of molten

calcium chloride.

Strontium and barium can also be obtained by

electrolysis, but are usually obtained by the high-

temperature reduction of their oxides, using aluminum

as the reducing agent.

Until recently, magnesium was obtained by the

electrolysis of molten MgCl2, in the Dow process. Less

expensive methods of obtaining magnesium are now

available.



Dow Process for Production of Mg

Electrolysis of Molten MgCl



Electrolysis of Molten MgCl2

Alloys of beryllium with other metals have many



y y y

applications such as springs, clips, and lightweight

structural materials.

Beryllium is nonsparking, and tools that must be usedin flammable atmospheres are sometimes made of

beryllium.

Magnesium has a lower density than any other structural metal and is an important metallurgical

reducing agent. Magnesium is also used in batteries

and fireworks.

Calcium is used to reduce the oxides or fluorides of

less common metals to the free metals. Calcium is

also alloyed with lead in lead –acid batteries, and is

used to form other alloys with aluminum and silicon.

The Group 2A Metals



The Group 2A Metals

and Living Matter

Persons of average size have approximately 25 g of magnesium in their bodies.

The recommended daily intake of magnesium for

adults is 350 mg. Calcium is essential to all living matter. The human

body typically contains from 1 to 1.5 kg of calcium.

Strontium is not essential to living matter, but it is of interest because of its chemical similarity to calcium.

Barium also has no known function in organisms; in

fact, the Ba2+ ion is toxic.

Ch i t f G d t



Chemistry of Groundwater

Rainwater containing dissolved CO2 is acidic

due to formation of H2CO3.

Acidic rainwater converts CaCO3 to Ca(HCO3)2:

• As the water evaporates from the Ca(HCO3)2, thesomewhat-soluble salt forms CaCO3 again.

Deposited CaCO3 leads to stalactites,

stalagmites, and other cave formations.

Hard Water and Water Softening



Hard Water and Water Softening Hard water is groundwater that contains

significant concentrations of ions (Ca2+,Mg2+, Fe2+) from natural sources.

Hard water tends to precipitate soaps,

reducing their effectiveness. If the primary anion is the hydrogen

carbonate ion (HCO3-), the hardness is

said to be tempo rary hardness . If the primary anions are other than

bicarbonate ion (Cl-, SO42-, HSO4

-)then the

hardness is called permanent hardness .



Soft: 0 - 20 mg/L as calcium

Moderately soft: 20 - 40 mg/L as calcium

Slightly hard: 40 - 60 mg/L as calcium

Moderately hard: 60 - 80 mg/L as calcium

Hard: 80 - 120 mg/L as calcium

Very Hard: >120 mg/L as calcium

3 3 2 2( ) M HCO MCO CO H O

Temporary Hard Water



Temporary Hard Water Contains HCO3

- ion.

When heated gives

CO32-, CO2 and H2O.

The CO32- reacts with

multivalent ions to form

precipitates.(for example CaCO3,

MgCO3)

Soften water byprecipitating the

multivalent ions using

slaked lime Ca(OH)2

Permanent Hard Water



Permanent Hard Water Contains significant concentrations of

anions other than carbonate.

For example SO42-, HSO4

-.

Usually soften by precipitating the Ca2+ and

Mg2+

using sodium carbonate leaving

sodium salts in solution.

Bathtub ring is caused by

salts of Mg2+ and Ca2+ of

Palmitic acid

(a common soluble soap).

Water Softening



Water Softening

Ion exchange.

Undesirablecations, Mg2+

Ca2+ and Fe3+

are changed for ions that are

not as

undesirable, ex.Na+.

Resins or

zeolites.

Water SofteningHard water

ith i



Water Softening

by Ion Exchangewith ions

An ion-exchange

resin with acidic

groups bound to Na+

As hard water passes

through, hard-watercations are

exchanged for Na+



D i i i



Deionizing

Instead of replacing cations withNa+, they are replaced with H+.

Then the anions are replaced withOH-.

H+(aq) + OH-(aq) → H2O(l)

Some studies have shown a weak inverse relationship

b t t h d d di l di i



between water hardness and cardiovascular disease in

men, up to a level of 170 mg calcium carbonate per litre

of water. The World Health Organization has reviewed the

evidence and concluded the data were inadequate toallow for a recommendation for a level of hardness.

A later review by František Kožíšek, M.D., Ph.D. National

Institute of Public Health, Czech Republic gives a good

overview of the topic, and conversely to the WHO, setssome recommendations for the maximum and minimum

levels of calcium (40-80 mg/L) and magnesium (20-30

mg/L) in drinking water, and a total hardness expressed

as the sum of the calcium and magnesium

concentrations of 2-4 mmol/L.

Naturally very soft water is more likely to corrode (i.e. react

chemically with) metal pipes in which it is carried, and as

a result it may have elevated levels of cadmium, copper,

lead and zinc.



150

2 2

o C Ca H CaH 22 2 Be TiO BeO Ti



2 2

610 /

22 2o H kJ mol Mg O MgO

3 2 2 2 36 3 ( ) 2Mg N H O Mg OH NH

2 2 2 4

2 2 2 2 2

4 2 ( )

2 ( )

Be C H O Be OH CH

CaC H O Ca OH C H

2 2 2

2 4 2 3 2

2 ( )

( ) 2 2 2

Mg H O Mg OH H

Mg OH NH Cl MgCl NH H O

2 2 4 2

2 2 2

2 2 ( )

2fuse

Be NaOH H O Na Be OH H

Be NaOH Na BeO H

Natri hidroxoberilat

Natri berilat

2 2 BeF Mg Be MgF

chuongtrinh chuong 8 9 group ia iia ok

Documents