PENGENALAN DASAR STRUKTUR ATOMBASIC INTRODUCTION TO ATOMIC STRUCTURE

ATOM IS THE BASIC UNIT OF MATTER COMPOSED OF ATOMIC NUCLEUS AND NEGATIVELY CHARGED ELECTRONS SURROUNDING IT.

The picture above is the picture

of atomic structure

Developing of Atomic Theory and Model

Democritus’

Atomic Theory

and Model

John Dalton’s Atomic

Theory and Model

J.J Thomson’s

Atomic Theory and

Model

Rutherford’s Atomic

Theory and Model

Bohr’s Atomic Theory

and Model

The modern View of Atomic

Theory and Model

1. DEMOCRITUS’ ATOMIC THEORY AND MODEL

Democritus, an ancient Greek’s philosopher who lived from 460 BC to 370 BC, has developed a matter composing theory.

According to Democritus, if a stone divided and we did it repeatedly until it is undivided

any more, every pieces of that stone had the same character with its origin. He labeled the smallest piece of a stone as atomos (A= no,

TOMos= divided), which mean “invisible”. Based on his theory, every atom that

constructed different matter is dissimilar.

2. JOHN DALTON’S ATOMIC THEORY AND MODELEven though Democritus named the technical terminology of atom, but the concept of atom as the smallest particle was published by John Dalton in 1803. John Dalton explained the model based on his calculation data while observing chemical reactions. Dalton suggested as followed a. Atom is the smallest particle of matterb. Atom is small sized and round shaped, indivisible, neither created nor destroyed.c. All atoms of given elements are identicald. Atoms of different elements can be joined to produce substance with fixed scalee. Atoms combine to make compound; a given compound always has the same relative number and kind of atoms  

3. J.J THOMSON’S ATOMIC THEORY AND MODEL

 

Dalton’s suggestion about atom as the smallest particle was broken after the discovery of electron by Thomson. In 1897, J.J Thomson did an experiment using cathode ray tube.

Atomic model by Thomson

4. RUTHERFORD’S ATOMIC THEORY AND MODEL

In almost the same time with Thomson’s experiment, four physicists, Henry Becquerel, Marie Curie, Pierre Curie, and Ernest Rutherford, had research with radioactivity. There were three kind of radioactive beams, alpha particle (α) was positively charge, beta particle (β) was negatively charge, and gamma particle (γ) was zero particle. The study of radioactivity gave a breakthrough to Rutherford for making his atomic model and theory.

5. BOHR’S ATOMIC THEORY AND MODEL

In 1913, Niels Bohr completed Rutherford’s theory by placing the

quantum theory of Planck and Einstein in it. According to Bohr, the electron

motion around the nucleus must progress in certain angle momentum.

According to Bohr, the maximum electron in every energy level was 2n2

6. THE MODERN VIEW OF ATOMIC THEORY AND MODELThe incapability of Bohr’s theory

in explaining atomic model aside from Hydrogen and the influence of magnetic field was accomplished in 1924 by Louis de Broglie. According to Broglie, beside as a particle, electron cam be defined as wave, whilst Bohr had assumed that electron was only defined as particle. This suggestion was improved by Erwin Schrodinger and Werner Heisenberg which generate the modern atomic model, known as mechanical quantum theory. The main principle of this theory is the electron motion in surrounding the nucleus performs characteristic of wave. The mechanical theory is used to explain atom and molecule behavior.  

DEVELOPMENT OF CHEMICAL ELEMENTS PERIODICAL SYSTEM

1. LAVOISIER ELEMENTS CLASSIFICATION METHOD

Group Gas Non-metal Metal Soil

Group Members

Light CalorOxygenNitrogenHydrogen

SulfurFosforChloride acidFluoride acidBorax acidBoric acid

AntimonArsenCobaltLeadManganmolibdenum

Gold TimbelZinc Mercury BismuthCopper

Iron Silver Nickel PlatinumTungsten

Calcium Magnesium BaritAluminasilica

Lavoisier Chemical Elements Classification

2. Dobereiner Elements Classification Method

Triad 1(Alkalin Metal)

Triad 2(Earth

Alkalin)

Triad 3(Halogen)

Triad 4(Group VI)

Lithium 7Sodium 23Potassium 39

Calcium40,08Stronsium87,62Barium137,34

Chlorin35,45Bromine

79,91Iodine 126,90

Sulfur32,06Selenium78,96Telurium127,60

3. CHANCOURTOIS ELEMENTS CLASSIFICATION METHOD

In 1862, a France geologist, Alexander Beguyer de Chancourtois, classified chemical elements based on its atomic weight raising. These

chemical elements were developed into spiral shaped arrangement

Atomic weight = 7 + 16n; n = element sequence

4. NEWLAND’S ELEMENTS CLASSIFICATION METHOD

H 1

F 8 Cl 15

Co/Ni 22

Br 29

Pd 36

I 43 Pt/Ir 50

Li 2

Na 9

K 16

Cu 23

Rb 30

Ag 37

Cs 44

Tl 51

G 3 Mg 10

Ca 17

Zn 24

Sr 31

Cd 38

Ba/V 45

Pb 52

Be 4

Al 11

Cr 18

Y 25

Ce/Le 32

U 39

Ta 46

Th 53

C 5 Si 12

Ti 19

In 26

Zr 33

Sn 40

W 47

Hg 54

N 6 P 13

Mn 20

As 27

Di/Mo 34

Sb 41

Nb 48

Bi 55

O 7 S 14

Fe 21

Se 28

Ro/Ru 35

Te 42

Au 49

Os 56

5. MENDELEEV’S ELEMENTS CLASSIFICATION METHOD

MEYER’S PERIODIC TABLE

6. MOSELEY’S ELEMENTS CLASSIFICATION METHODIn 1909 and 1911, Ernest Rutherford found one of the base particles

inside the atom, that is proton, and the nucleus. According to Rutherford, atom is acompiled of positively charged atomic nucleus surrounded by negatively electrons in circle. If a metal is shot with high energy electron, X-ray will be emitted. Base on Rutherford’s findings, Henry Moseley studied X-ray and its correlation with the amount of electrical charge using X-ray spectroscopy. Then, he plotted the X-ray frequence with the increasing of atomic number. The results show linear trend that revealed the correlation between atomic number and atomic properties periodically. After that, Moseley arranged the elements based on the increasing of atomic number in the periodic table form.

 

7. SEABORG’S ELEMENTS CLASSIFICATION METHOD

In 1940, Glenn Seaborg discovered trans-uranium, the elements with atomic

number of 94-102. This finding triggered some difficulties concerning the trans-uranium elements position in periodic table. This problem is finally solved by

composing new rows ang generally changed the modern periodic table.

Atom’s Basic Particle

1. ELECTRON

Cathode ray tube experiment was first performed William Crookes (1875). The results of his experiment was the

discovery of a beam emerging from the cathode to the anode is called the cathode. George Johnstone Stoney (1891) which provides a cathode ray called "electrons". The weakness of Stoney could not explain the notion of atoms in an element have the same properties while different elements will have different properties, although both have electrons. Antoine Henri Becquerel (1896) determine the rays emitted from

radioactive elements in nature similar to the electron. Joseph John Thomson (1897) William Crookes experiment continued

influence of the electric field and magnetic fields in cathode ray tube.

2. Proton

If 0 is the electron mass a particle has no mass when the particle has a mass of material that can be

measured. So did the fact that the atom was neutral. How could it be neutral atoms and have, if there are

only electrons in atoms? Eugene Goldstein (1886) conducted experiments of gas

cylinders which have a cathode, the holes were and given an electric charge. It turned out that the

electrons formed at the anode to the positive rays are formed that led to the opposite direction through the hole at the cathode. After the various gases tested in

this tube, hydrogen is the gas that produces light of the positive charge of both the smallest mass or load, so that these particles called protons. Proton mass = 1

sma (atomic mass units) and the proton charge = +1

4. NEUTRON

 Prediction of W. Rutherford Bothe and H. Becker (1930) conducted experiments on alpha particle bombardment nuclei of beryllium (Be). It turned out that the particle radiation produced a high penetrating power. The experiment was continued by James Chadwick (1932). It turned out that the radiation particles that cause the high penetrating power is neutral or no charge and its mass is almost equal to the proton. These particles called neutrons.

CALCULATE THE AMOUNT OF PROTON, ELECTRON, AND NEUTRON OF ATOM

 X = Atom or elements symbolA = mass number = total proton and

neutronZ = atomic number = amount of

proton 

Proton and electron have opposite charge. If the total amount of proton and electron is the same, the atom will have zero

charge. But if the total amount of proton and electron is different, then atom will charge either positive or negative. Charged atom is called ion. Positive ion is named cation and

negative ion is named anion.

THE ELECTRON STRUCTURE OF ATOM (ELECTRON CONFIGURATION)

AtomicElements

Electron’s number ValenceElectrons

AtomicElements

Electron’s number ValenceElectrons

K L M N K L M N

1He 1 1 11Na 2 8 1 1

2He 2 2 12Mg 2 8 2 2

3Li 2 1 1 13Al 2 8 3 3

4Be 2 2 2 14Si 2 8 4 4

5B 2 3 3 15P 2 8 5 5

6C 2 4 4 16S 2 8 6 6

7N 2 5 5 17Cl 2 8 7 7

8O 2 6 6 18Ar 2 8 8 8

9F 2 7 7 19K 2 8 8 1 1

10Ne 2 8 8 20Ca 2 8 8 2 2

Atomic Electron Configuration of Atomic number within 1-20

CORRELATION OF ELECTRON CONFIGURATION WITH PERIOD AND GROUP

The electron configuration of atom can be used to determine an atom position in periodic table. The group number is determined from the number of its valence electron. While the period number

is obtained from the total number of shell filled with electron.

Group Number = valence electron

Period Number = number of shell filled with electrons

Group Number = valence electron

Period Number = number of shell filled with electrons

THE ATOMIC RELATIVE MASS OF ELEMENTS

In the beginning, hydrogen was used as standard. Then after that, oxygen began to be used as standard, substitusing hydrogen. In 1961, carbon was used a standard. Atomic mass (in grams) has a very small value. Therefore, scientist agreed to label atomic mass unit (amu) as standard mass for atom. The value of 1 amu is equal to 1/12 of one atomic mass of C-12. 1 amu = 1/12 x 1 atomic mass of C-12 = 1/12 x 1.99268 x 10-

23 gram = 1.66 x 10-24 gram 

 CATEGORIZING ELEMENTS INTO ISOTOPE, ISOBAR AND ISOTON

1. ISOTOPE

Isotopes are atoms that have the same atomic number but have different mass numbers. Each isotope of an element have the same chemical properties because the same number of valence electrons

Example :

2. ISOBAR

Isobar is the elements that have different atomic numbers but the same mass number.  Example:

3. ISOTON

Atoms are different but have the same number of neutrons.  Example:

THE END

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