2. PRIMERAS TEORÍAS ATÓMICAS
ALREADY IN THE IVTH CENTURY a.C. DEMÓCRITO SAID THAT
THE MATTER WAS DISCONTINUOUS AND THAT IT COULD NOT
DIVIDE INDEFINITELY. AFTER SEVERAL DIVISIONS IT WOULD
ARRIVE TO AN INDIVISIBLE UNITY, WHICH IT CALLED ATOMO,
WHICH IN GREEK MEANS "THAT CAN NOT BE CUT".
ON THE CONTRARY, ARISTÓTELES BELIEVED THAT THE
MATTER WAS CONTINUOUS AND WAS FORMED BY 4
ELEMENTS: EARTH, AIR, WATER AND FIRE. THIS THEORY WAS
ACCEPTED FOR MORE THAN 2000 YEARS
3. ATOMIC MODEL OF DALTON
IN 1808 JOHN DALTON PUBLISHED THE FIRST ATOMIC THEORY BASED ON
SCIENTIFIC DATA. IT IS BASED ON 5 POSTULATES:
1. MATTER IS FORMED BY INDIVISIBLE ATOMS.
2. EACH ELEMENT IS FORMED BY EQUAL ATOMS, WITH THE SAME MASS AND
THE SAME CHEMICAL PROPERTIES.
3. THE ATOMS OF DIFFERENT ELEMENTS HAVE DIFFERENT MASS AND
CHEMICAL PROPERTIES.
4. IN THE CHEMICAL REACTIONS, THE ATOMS NEITHER ARE CREATED OR
DESTROYED, ONLY CHANGE THEIR DISTRIBUTION IN THE SUBSTANCES.
5. THE ATOMS OF DIFFERENT ELEMENTS COMBINE TO FORM CHEMICAL
COMPOUNDS, AND THEY DO ALWAYS IN A FIXED RATIO.
4. ATOMIC MODEL OF DALTON
4. EXTRACCIÓN DE CONCLUSIONES. JHON OBSERVA QUE SU
HIPÓTESIS ES CIERTA, QUE INDEPENDIENTEMENTE DE SU MASA
TODOS LOS OBJETOS SON ATRAÍDOS HACIA LA TIERRA CON LA
MISMA FUERZA, LA FUERZA DE LA GRAVEDAD.
5. COMUNICACIÓN DE RESULTADOS. JHON ELABORA UN INFORME
EN EL QUE REFLEJA EL DESARROLLO DE SU INVESTIGACIÓN Y SUS
RESULTADOS, Y LO EXPONE EN EL TABLÓN DE ANUNCIOS DEL
INSTITUTO.
SE COLOCA DELANTE HACIENDO MALABARES PARA DARLE
PUBLICIDAD A SU INVESTIGACIÓN.
7. THE ELECTRICAL NATURE OF THE MATTER
THE ELECTRONIC PHENOMENA ARE JUSTIFIED THROUGH A PROPERTY OF
THE MATTER CALLED AMOUNT OF ELECTRICAL CHARGE (Q) WHOSE UNIT IN
THE INTERNATIONAL SYSTEM IS THE COULOMB (C).
ELECTRONIC PHENOMENA SHOW THAT THE ATOM IS DIVISIBLE AND THAT IS
FORMED BY SMALLER PARTICLES THAT HAVE ELECTRIC CHARGE. J.J.
THOMSON IDENTIFIED THE ELECTRON AS THE NEGATIVE ELECTRIC CHARGE
PARTICLE THAT COMPOSE AN ATOM, WHILE E. GOLDSTEIN IDENTIFIED THE
PROTON LIKE THE PARTICLE WITH POSITIVE ELECTRICAL CHARGE OF THE
ATOM.
9. THE ELECTRICAL NATURE OF THE MATTER
THE ELECTRON CHARGE IS THE SMALLEST, THEREFORE RECEIVES THE
NAME OF THE ELEMENTAL ELECTRICAL CHARGE.
A BODY IS ELECTRICALLY NEUTRAL WHEN THE NUMBER OF PROTONS THAT
IT POSSESS IS EQUAL TO THE NUMBER OF ELECTRONS. BECAUSE THE
PROTONS ARE FOUND IN THE NUCLEUS, A BODY CAN ONLY ACQUIRE
ELECTRIC CHARGE WHEN IT WINS OR LOSES ELECTRONS. IF THE BODY
LOSES ELECTRONS, IT WILL BE POSITIVELY CHARGED, AND IF THE BODY
WINS IT WILL BE NEGATIVELY CHARGED .
TWO BODIES WITH CHARGES OF THE SAME TYPE ARE REPELLERED, AND
WILL BE ATTRACTED IF THEY HAVE CHARGES OF DIFFERENT TYPE.
13. ATOMIC MODELS OF THE 20TH CENTURY
THE DISCOVERIES OF ELECTRON AND PROTON ARE INCOMPATIBLE WITH AN
INDIVISIBLE ATOM MODEL (MODEL OF DALTON), SO THAT A CAREER BEGINS
TO DISCOVER THE MODEL THAT EXPLAINS HOW THE SUBTOMATIC
PARTICLES ARE LOCATED INSIDE THE ATOM.
• IN 1904 J.J. THOMSON PROPOSE AN ATOMIC MODEL IN WHICH THE ATOM IS
A CONTINUOUS POSITIVE CHARGE SPHERE ON WHICH THE ELECTRONS
APPEAR LIKE THE SEEDS OF A WATERMELON.
14. ATOMIC MODELS OF THE 20TH CENTURY
• IN 1909 E. RUTHERFORD BOMBS A VERY FINE GOLD FOIL WITH PARTICLES CHARGED
POSITIVELY AND AT GREAT SPEED. TO THE CONTRARY OF THE EXPECTED FOLLOWING
THE THOMSON MODEL, SOME PARTICLES DEFLECTED CONSIDERABLY, AND SOME EVEN
REBOUND TOWARDS THE EMISSION SOURCE, ALTHOUGH THE MAJORITY CAME
THROUGH THE SHEET WITHOUT DEFLECTING.
15. ATOMIC MODELS OF THE 20TH CENTURY
• RUTHERFORD CONCLUDED THE FOLLOWING:
MOST OF THE POSITIVE PARTICLES PROJECTED ABOVE THE ATOM DO NOT
REFLECT BECAUSE THE ATOM IS IN THE MOST PART A VACUUM SPACE.
SOME PARTICLES DEVIATE SLIGHTLY BECAUSE THEY HAVE PASSED NEAR A
ZONE WITH POSITIVE CHARGE, AND HAVE BEEN REPELLED.
OTHER PARTICLES REBOUNDED BY BANGING DIRECTLY WITH A VERY DENSE
AND STRONGLY POSITIVE AREA THAT DENOMINATED ATOMIC NUCLEUS.
16. ATOMIC MODELS OF THE 20TH CENTURY
• RUTHERFORD DESCRIBED AN ATOMIC NUCLEAR MODEL WITH TWO
DIFFERENTIATED ZONES:
-A CENTRAL AREA VERY SMALL, VERY DENSE AND POSITIVELY CHARGED,
WHERE THE PROTONS ARE LOCATED.
-A PERIPHERAL ZONE IN WHICH THE ELECTRONS, NEGATIVELY CHARGED,
ROTATE AROUND THE NUCLEUS AT A DISTANCE FROM HIM.
-THIS MODEL IS ALSO KNOWN AS A PLANETARY MODEL OF RUTHERFORD
BECAUSE ITS STRUCTURE IS SIMILAR TO THE SOLAR SYSTEM.
18. ATOMIC MODELS OF THE 20TH CENTURY
-THE MODEL OF RUTHERFORD HAD AN EVIDENT PROBLEM, THE SUM OF THE
MASS OF THE PROTONS AND THE ELECTRONS OF AN ATOM WAS LESS TO
THE MASS OF THE ATOM. WHY THE RUTHERFORD HAD PREDICTED THE
EXISTENCE OF A PARTICLE IN THE NUCLEUS WITH MASS BUT WITHOUT
CHARGE.
-IN 1932, J. CHADWICK DISCOVERED THE NEUTRON AND INCORPORATED IT
INTO THE PLANETARY MODEL OF RUTHERFORD, REMAINING:
-A CENTRAL ZONE VERY SMALL , VERY DENSE AND POSITIVELY CHARGED,
WHERE PRACTICALLY ALL THE MASS IS CONCENTRATED, WHICH PROTONS
AND NEUTRONS.
-A PERIPHERAL ZONE IN WHICH THE ELECTRONS, NEGATIVELY CHARGED,
ROTATE AROUND THE NUCLEUS AT A RIGHT DISTANCE OF HIM AT A GREAT
SPEED.
20. FORMATION OF IONS
AN ELECTRICALLY NEUTRAL ATOM WILL HAVE THE SAME NUMBER OF
PROTONS THAN ELECTRONS.
WHEN AN ATOM HAS ELECTRIC CHARGE, IT MEANS THAT ITS NUMBER OF
PROTONS AND ELECTRONS WILL NOT BE THE SAME, CALLING ION.
THERE ARE 2 TYPES OF IONS:
• WHEN THE ATOM LOSES AN ELECTRON IS CHARGED POSITIVELY, CALLING
CATIÓN.
• WHEN THE ATOM WINS AN ELECTRON IS NEGATIVELY CHARGED, NAMING
ANION.
22. IDENTIFICATION OF ATOMS
-THE ATOMS ARE IDENTIFIED BY:
-THE ATOMIC NUMBER (Z) APPEARS AS A SUB-INDEX BEFORE THE ELEMENT, AND IT IS THE NUMBER OF
PROTONS THAT HAVE THAT ELEMENT IN ITS NUCLEUS.
-THE MASS NUMBER (A) IS REPRESENTED AS A SUPER-INDEX BEFORE THE ELEMENT, AND IT IS THE
SUM OF THE PROTONS AND NEUTRONS THAT HAVE THAT ELEMENT IN ITS NUCLEUS.
A= NUMBER OF PROTONS + NUMBER OF NEUTRONS
NUMBER OF NEUTRONS= A-Z.
23. THE ISOTOPES
-NOT ALL THE ATOMS OF THE SAME ELEMENT HAVE THE SAME MASS
NUMBER. THE ATOMS OF THE SAME ELEMENT THAT HAVE THE SAME NUMBER
OF PROTONS BUT DIFFERENT NUMBER OF NEUTRONS ARE DENOMINATED
ISOTOPES. FOR EXAMPLE, THE HYDROGEN ISOTOPES ARE:
25. BOHR ATOMIC MODEL
ACCORDING TO THE MODEL OF RUTHERFORD, ELECTRONS WILL ROTATE AT
GREAT SPEED AT AN UNKNOWN DISTANCE. BUT, AS ANY ELECTRIC CHARGE
THAT TURNS EMITTES ENERGY IN THE FORM OF RADIATION, IT WILL GO
LOSING ENERGY AND IT WILL GO CLOSER TO THE NUCLEUS UNTIL IT FALLS
ON IT.
NIELS BOHR IN 1913, FINISHED WITH THIS INCONGRUENCE THROUGH A NEW
MODEL BASED ON 2 POSTULATES:
1. THE ELECTRON MOVES IN CERTAIN CIRCULAR ORBITS WITHOUT ENERGY
EMISSION. THE ENERGY THAT IS POSSESSED WILL BE GREATER WHEN
MORE REMOVED IT IS FROM THE NUCLEUS.
2. THE EMISSION OF ENERGY ONLY HAPPENS WHEN AN ELECTRON JUMPED
FROM AN ORBIT OF GREATER ENERGY TO ANOTHER OF LOWER ENERGY.
26. BOHR ATOMIC MODEL
HACER EJERCICIOS 27 PÁGINA 45,
28, 30,31,32,33,34,35 PÁGINA 46. PARA EL VIERNES QUE VIENE.
27. BOHR ATOMIC MODEL
ACCORDING TO THIS MODEL, THE ELECTRONS ARE DISTRIBUTED IN LEVELS
AND SUB-LEVELS THAT ADMIT A MAXIMUM NUMBER OF ELECTRONS:
28. BOHR ATOMIC MODEL
THE DISTRIBUTION BY LEVELS OF THE ELECTRONS OF AN ATOM OF AN
ELEMENT RECEIVES THE NAME OF ELECTRONIC CONFIGURATION OF THE
ELEMENT. VALENCE ELECTRONS ARE THOSE LOCATED AT THE LAST
ENERGETIC LEVEL, AND ARE RESPONSIBLE FOR THE CHEMICAL PROPERTIES
OF THE MATTER.
TO DRAW THE NUCLEUS OF AN ATOM, WE WILL TRACE A CENTRAL CIRCLE
AND INSIDE IT WE WILL PLACE THE NUMBER OF PROTONS (WITH THE SIGN +)
AND NEUTRONS, WHICH WE WILL CALCULATE FROM THE ATOMIC AND
MASSIC NUMBERS.
NUMBER OF PROTONS(Z)= 11
NUMBER OF NEUTRONS (A-Z)=23-11=12
29. DRAW ATOMS
AROUND THE NUCLEUS WE PLACED THE ELECTRONS, DISTRIBUTED AT THE
DIFFERENT ENERGETIC LEVELS (ORBITS). IN A NEUTRAL ATOM THE NUMBER
OF ELECTRONS IS EQUAL TO PROTONS, SO WE SHOULD DISTRIBUTE
BETWEEN THE DIFFERENT LEVELS 11 ELECTRONS IN OUR ATOM OF SODIUM
(Na). YOUR CONFIGURATION WOULD BE: 2S 2S 6P 1S.
30. EXERCISES
1. DRAW Mg ATOM KNOWING Z=12 Y A=24.
2. DRAW Al ATOM KNOWING Z=13 Y A=27.
3. DRAW IÓN AL+3
31. THE RADIACTIVITY
THE NUCLEUS OF SOME ELEMENTS ARE NOT STABLE, BECAUSE THEY HAVE
A NUMBER OF NEUTRONS VERY HIGHER THAN THAT OF PROTONS. TO GET
STABLE, THESE NUCLEUS ISSUE PARTICLES AND RADIATIONS
TRANSFORMING ON OTHER ELEMENTS. THIS PHENOMENON DISCOVERED BY
HENRI BECQUEREL IN 1896 RECEIVES THE NAME OF RADIACTIVITY.
RADIATIONS ISSUED BY RADIOACTIVE NUCLEUS CAN BE OF 3 TYPES:
• ALPHA RADIATION: ALPHA PARTICLES CONSIST OF 2 PROTONS AND 2
NEUTRONS, SO THEY HAVE POSITIVE CHARGE. THEIR POWER OF
PENETRATION IS VERY LOW, A FEW PAPER SHEETS OR OUR OWN SKIN CAN
STOP THEM.
• BETA RADIATION: FORMED BY ELECTRONS, THEREFORE HAS NEGATIVE
CHARGE. THEY HAVE A CONSIDERABLE POWER OF PENETRATION, BEING
ABLE TO PASS THROUGH ALUMINUM SHEETS OF A THICKNESS OF 5mm.
• GAMMA RADIATION: IT IS A NO-CHARGE ENERGY RADIATION. GREAT POWER
OF PENETRATION, TO AVOID THEIR PASS LEAD OR CONCRETE PLATES OF
MORE THAN 25 mm THICKNESS ARE REQUIRED.
32. EJERCICIOS
1. DIBUJA EL ÁTOMO DE Mg SABIENDO QUE Z=12 Y A=24.
2. DIBUJA EL ÁTOMO DE Al SABIENDO QUE Z=13 Y A=27.
3. DIBUJA EL IÓN AL+3
33. THE RADIACTIVITY
RADIOISOTOPES ARE RADIOACTIVE ISOTOPES OF AN ELEMENT. FOR EXAMPLE, CARBON
14, URANIO 235 OR RADIO 226.
RADIOACTIVE ISOTOPES ARE USED IN MEDICINE FOR THE DIAGNOSIS AND TREATMENT
OF SOME DISEASES. FOR EXAMPLE TO DIAGNOSE THE THYROID CANCER IODINE 132 IS
SUPPLIED, WHICH WILL HAVE TO ACCUMULATE IN CANCER CELLS MARKING ITS
PRESENCE. IN THE TREATMENT, IODINE 131 IS USED THAT EMITS PARTICLES THAT CAN
DESTROY CANCER CELLS (RADIOTHERAPY).
RADIOACTIVE ISOTOPES ARE ALSO USED IN PALEONTOLOGY TO DATE ANTIQUE
OBJECTS WITH GREAT ACCURACY. CARBON 14 IS IN NATURE NATURALLY AND IN
BALANCE WITH THE RADIOACTIVE ISOTOPE C12.
WHEN SOMEBODY DIE THE C14 BEGINS TO DISINTEGRATE DIMINISHING HIS
CONCENTRATION AS THE TIME PASSES. MEASURING THE AMOUNT OF C14 IN A SAMPLE
WE CAN KNOW THE ANTIQUITY OF THE ORGANIC REMAINS.
34. THE RADIACTIVITY
RADIOISOTOPES ARE USED IN AGRICULTURE FOR THE CONTROL OF PESTS AND THE
CONSERVATION OF FOOD, WHILE IN THE INDUSTRY IT IS USED TO DETECT
CONSTRUCTION FAULTS.
NUCLEAR ENERGY IS ORIGINATED BY A FISSION PROCESS OF URANIO-235 WHEN IT IS
BOMBED WITH A NEUTRON. IN A NUCLEAR POWER PLANT THE ENERGY RELEASED IN
THE FISSION IS USED TO HEAT WATER THAT, CONVERTED IN STEAM, ACTIVATES A
TURBINE UNITED TO A GENERATOR THAT PRODUCES ELECTRICITY.
36. RADIOACTIVE WASTE MANAGEMENT
IN SPAIN THE COMPANY THAT MANAGES RADIACTIVE WASTE IS ENRESA.
LOW AND MEDIUM ACTIVITY WASTE MANAGEMENT: THEY ARE IMMOBILIZED
IN CONTAINERS WITH A SOLID MATRIX OF CONCRETE AND ARE STORED IN AN
ENGINEERING BARRIER THAT IS INTRODUCED INTO A GEOLOGICAL BARRIER,
WHICH WILL BE UNDERGROUND STORAGE AT A GREAT DEPTH. THE RESIDUE
ACTIVITY IS REDUCED BY 70% IN THE FIRST DECADES, ALTHOUGH THEY WILL
REMAIN BURIED MORE THAN 200 YEARS. IN SPAIN THE PLANT OF
MANAGEMENT OF THESE WASTE IS LOCATED IN EL CABRIL (CÓRDOBA).
HIGH ACTIVITY WASTE MANAGEMENT: THEY ARE STORED TO GREATER
DEPTH AND WILL BE BURIED DURING THOUSANDS OF YEARS. IN SPAIN ARE
TRYING TO BUILD IN VILLAR DE CAÑAS (CUENCA), ALTHOUGH THE PROJECTS
IS PARALIZED BY THE BOARD OF CASTILLA LA MANCHA.
37. LA RADIACTIVIDAD
LOS RADIOISÓTOPOS SON ISÓTOPOS RADIACTIVOS DE UN ELEMENTO. POR EJEMPLO
EL CARBONO 14, EL URANIO 235 O EL RADIO 226.
LOS ISÓTOPOS RADIACTIVOS SE UTILIZAN EN MEDICINA PARA EL DIAGNÓSTICO Y
TRATAMIENTO DE ALGUNAS ENFERMEDADES. POR EJEMPLO PARA DIAGNOSTICAR EL
CÁNCER DE TIROIDES SE SUMINISTRA YODO 132, QUE TENDERÁ A ACUMULARSE EN
CÉLULAS CANCERÍGENAS MARCANDO SU PRESENCIA. EN EL TRATAMIENTO SE UTILIZA
YODO 131 QUE EMITE PARTÍCULAS QUE PUEDEN DESTRUIR LAS CÉLULAS CANCEROSAS
(RADIOTERAPIA).
LOS ISÓTOPOS RADIACTIVOS TAMBIÉN SE UTILIZAN EN PALEONTOLOGÍA PARA DATAR
OBJETOS ANTIGUOS CON GRAN EXACTITUD. EL CARBONO 14 SE ENCUENTRA EN LA
NATURALEZA DE FORMA NATURAL Y EN EQUILIBRIO CON EL ISÓTOPO NO RADIACTIVO
C12.
AL MORIR UN SER VIVO EL C14 COMIENZA A DESINTEGRARSE DISMINUYENDO SU
CONCENTRACIÓN CONFORME PASA EL TIEMPO. ASÍ MIDIENDO LA CANTIDAD DE C14 EN
UNA MUESTRA PODEMOS CONOCER LA ANTIGÜEDAD DE LOS RESTOS ORGÁNICOS.
LOS RADIOISÓTOPOS SE UTILIZAN EN AGRICULTURA PARA EL CONTROL DE PLAGAS Y
LA CONSERVACIÓN DE ALIMENTOS, MIENTRAS QUE EN LA INDUSTRIA SIRVE PARA
DETECTAR FALLOS DE CONSTRUCCIÓN DE PIEZAS.
