standar kompetensi: memahami struktur atom, sifat-sifat periodik unsur, dan ikatan kimia

Periodical Development By Farid 2008

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Standar Kompetensi : 1. Memahami struktur atom, sifat-sifat periodik

unsur, dan ikatan kimiaKompetensi dasar:1.1. Memahami struktur atom berdasarkan teori

atom Bohr, sifat-sifat unsur, massa atom relatif, dan sifat-sifat periodik unsur dalam tabel periodik serta menyadari keteraturannya, melalui pemahaman konfigurasi elektron.

Indikator:1. Membandingkan perkembangan tabel periodik

unsur untuk mengidentifikasi kelebihan dan kekurangannya.

2. Menjelaskan dasar pengelompokan unsur-unsur.


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At present, scientists have succesfuly finding and identify about 118 element, and 90 element among other are the element which there are in nature (nature element), while the remainder (sisanya) are the artificial elements (unsure buatan). Because of the elements in nature are plenty (sangat banyak), hence to facilitate (memudahkan) us to study and identify a given element. The scientists try to group the elements in a given group based on their similar properties.


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For begining, elements are grouped on their metallic properties based only, those are become the metallic elements, nonmetallic elements and semi metallic elements (metalloid). However, then element grouped in periodic tables based on atomic number and atomic mass number of that elements. The following are explanations about history of element grouping development since early until present.


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Some properties of metal group are:

1. Shine

2. Good electrical and heat conductor

3. Can be processed as metalwork (dapat ditempa)

4. Hard or Not brittle (tidak rapuh)

5. Mostly on solid form, except for mercury which has liquid form.


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1. Dobreiner TriadsAccording to Johann Wolfgang Dobreiner, if a triad

consist of element A, B and C, so the average sum of atomic mass of A and atomic mass of B is equal to the atomic mass of C. In this case A, B and C are the element with similar properties.

The examples of triads are :Cl , Br , I Ca, Sr , BaS , Se , TeFe,Co , Mn


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2. Newlands OctaveIn 1859 the German physicists John A.R.

newlands listed the elements in the order based on the increase of atomic weights and he noted that a given properties of the elements in the list, recurs at every eighth element.

Meanwhile its weakness , along with the discovery of more new elements, there were many of them that have similarity in properties but the total was more than three.

For example, fluorine was similar with the halogen triad (chlorine, bromine, iodine)


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Newlands calssified chemical elements based on its atomic weight mounting. Newlands found the linkage between element properties and atomic weight rising.

Element properties will be repeated after every eight element (octave law).

It means that the 8th element will have similar properties with the 1st element.


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1 2 3 4 5 6 7

H Li Be B C N O

F Na Mg Al Si P S

Cl K Ca Cr Ti Mn Fe

Co, Ni Cu Zn Y In As Se


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H F Cl Co/Ni Br Pd I Pt/Ir

Li Na K Cu Rb Ag Cs Tl

Be Mg Ca Zn Sr Cd Ba/V Pb

B Al Cr Y Ce/La U Ta Th

C Si Ti In Zr Sn W Hg

N P Mn As Di/Mo Sb Nb Bi

O S Fe Se Ro/Ru Te Au Os


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Newlands octave has the excess (kelebihan) compared than Dobreiner triads, that is the more classified elements.Meanwhile, its weakness is at element which its mass is large enough (>40), the element properties repletion is not happened any more, so that elemens grouping based on Newlands octave is not used in present day. or the law octaves has weakness that is the suitable only at elements which its mass is small.


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3. Mendeleev’s Periodic TableIndependently, Russian chemist Dmitry Mendeleev

in 1869 and German chemist Julius Lothar Meyer in 1870 proposed a chemical law that the properties of all the elements are periodic functions of their atomic mass. According to that the law (periodic law), Mendeleev and Meyer grouped about 66 elements based on the increases of their atomic mass.Mendeleev give a place elements having similar properties in a coulomn called GROUP.


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Reihen(Periode)

Grouppe I

Grouppe II

Grouppe III

Grouppe IV

Grouppe V

Grouppe VI

Grouppe VII

Grouppe VIII

1 H=1

2 Li=7 Be= 9,2 B= 11 C= 12 N= 14 O= 16 F= 19

3 Na= 23 Mg= 24 Al= 27,3 Si= 28 P= 31 S= 32 Cl= 35,5

4 K= 39 Ca= 40 - = 44 Tl= 48 V= 51 Cr= 52 Mn= 55 F=56, Co=59

5 (Cu= 63) Zn= 65 - = 68 - = 72 As= 75 Se= 78 Br= 80

6 Rb= 85 Sr= 87 ?Yt= 88 Zr= 90 Nb= 94 Mo= 96 - = 100 Ru=104, Rh=104Pd=106, Ag=108

7 (Ag= 108) Cd=112 In= 113 Sn= 118 Sb= 122 Te= 125 J= 127

8 Cs= 133 Ba= 137 ? Di= 138 - - - - ------

9 - - - - - -

10 - - ? Er= 178 ? La= 180

Ta= 182 W= 184 - Os=195, Ir=197Pt=198, Au=199

11 (Au=199) Hg= 200 Ti= 204 Pb= 207 Bi= 208 -

12 - - Th= 231 - U= 240 - ------


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Mendeleev’s Periodic table has some excess compared than Newlands Octave, those are:Giving correction to some values of relative atomic mass of the element. The example of the relative atomic mass of Uranium is changed from 10 become 240 and Beryllium for 13 become 9.Mendeleev take place the tellurium element (128) before iodine (127).


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Mendeleev’s Periodic table (has weakness) is still has the lack (kekurangan), that is some sequence (urutan) of the elements placement apparently (ternyata) inappropriate (unsuitable) with the increase of their atomic mass.

Mendeleev set a side a vacant space (ruang kosong) from his table. Then this place was later assigned to the element scandium, discovered in 1879, which has properties justifying its position in that periodic table.The placement of the noble gasses in the mendeleev’s periodic table do not modify the early formation of the other elements.


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4. Short-Form Periodic TableThe raising of new element discoveries during period

of 1817-1898 caused the Mendeleev’s periodic table become no longer be relevant to classify the element. Therefore, in 1930 the scientists developed the new periodic table which is the development of mendeleev’s periodic table. The periodic table is recognized (dikenal) as the short-form periodic table.


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Group 0

I II III IV V VI VII VIII

a b a b a b a b a b

a b a b

a b

H

He Li Be B C N O F

Ne Na Mg Al Si P S Cl

Ar K Cu

Ca Zn

Sc Ga Ti Ge

V As

Cr Se

Mn Br

Fe,Co,Ni

Kr Rb Ag

Sr Cd Y In Zr Sn

Nb Sb

Mo Te

- 153

Ru,Rh,Pd

Xe Cs Au

Ba Hg

57-71* Tl

Hf Pb

Ta Bi

W Po

Re - Os,Ir,Pt

Rn Ra Ac Th Pa U


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5. Long-Form Periodic table (Modern Periodic Table)In 1914 Henry G.J. Moseley found that the properties

of element are periodic function of their atomic number. Based on that case, so the short-form periodic table developed become the long-form periodic table, then this periodic table completed become the modern periodic table ratified (disahkan) its use by IUPAC (The International Union of Pure and Applied Chemists) in 1923.In modern periodic table, element take placed at row called period and group. In this case, period is the placement row of the elements is in the horizontal lines, meanwhile, group is the placement of the elements is in the vertical columns.


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PeriodPlacement of element in period are relied (didasarkan) on the periodical properties of element that according to the order of their atomic number alteration (perubahan). In modern periodic table, element are grouped into 7 period that consist of:

shortest period (period 1 consist of 2 elements)short period (period 2 and period 3, each consist of 8 elements)Long period (period 4 and period 5, each consist of 18 elements)Longest period (period 6, consist of 32 elements)Uncomplete period (period 7)


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GroupElements which take placed in one group are the elements having the similar properties of one another . The group of element in periodic table is distinguished (dibedakan) into principal group (group A) and transition group (group B)


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Modern Periodic System (Moseley)

Element characteristics are the periodic function of the atom number-NOT the atom mass.

In the year of 1985, IUPAC establishes (menetapkan) a Modern Periodic System.


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B. Groups Periods of Elements in Periodic System

1. Group

Group are columns in periodic system


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Modern Periodic System

Consists of :

a. 8 major groups ( I A – VIII A )

b. 8 Transition groups ( I B – III B )

c. Internal transition groups ( Lantanida and Actinida )


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For major groups, they are:

a. IA group ( alkaline metal group)

Li , Na , K , Rb , Cs , Fr

b. IIA group ( earth alkaline metal group )

Be , Mg , Ca , Sr , Ba , Ra

c. IIIA group ( aluminium group )

B , Al , Ga , In , Tl


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d. IVA group ( carbon group )

Ca , Si , Ge , Sn , Pb

e. VA group ( nitrogen group )

N , P , As , Sb , Bi

f. VIA group ( khalkogen / oxygen group )

O , S , Se , Te , Po

g. VIIA group ( halogen group )

He , Ne , Ar , Kr , Xe , Rn

standar kompetensi: memahami struktur atom, sifat-sifat periodik unsur, dan ikatan kimia

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