teori atom

  TEORI ATOM (Munculnya Kimia Modern)Pendahuluan Konsep tentang atom sebenarnya sudah ada sejak jaman Yunani Kuno. Konsep itu kemudian timbul tenggelam sampai abad pertengahan. Dengan banyaknya eksperimen tentang gas dan vakum sesudah Galileo (misalnya oleh Torricelli [pernah menjadi murid Galileo] tentang kolom air raksa yang ditahan tekanan udara 1 atmosfer) maka teori atom menjadi mengemuka untuk memberikan penjelasan.As we have seen, the atomistic hypotheses up to the nineteenth century had not given rise to an unambiguous and precise theory either ofmatter or of heat.  [Teori atom belum menjadi paradigma.]
Yet, between the publication of Robert Boyle's Sceptical Chymist in 1661 and Lavoisier's death in 1794 [dengan pisau guillotine !], there had developed  a  fundamental concept that was destined to give a new, vital, and precise meaning to the speculative atomistic hypothesis. This concept wasthe chemical element. [Munculnya kimia modern]
Teori atom kemudian mendapatkan dukungan yang kuat dengan munculnya konsep unsur kimia.
Munculnya teori atom sudah diawali pada jaman kuno, namun diterimanya sebagai paradigma bersamaan dengan munculnya kimia modern. Teori atom diperlukan bagi perkembangan kimia (terutama tentang reaksi kimia, bidang garapan utama ilmu kimia).By the end of the eighteenth century, chemists had come to accept this operational definition of element: It is a substance that cannot be decomposed into other substances by chemical or physical
means means available at the present time.

Whether
these elements would in the future turn out to be really compounds of yet more basic substances was a question that could safely be left to metaphysicians, or to future scientists.Teori atom yang pertama sekali cukup komprehensif adalah oleh Dalton.
Perhatikan judul bukunya : A New System of Chemical Philosophy.a) Each particle of a gas is surrounded by an atmosphere of caloric.

b) The particles are essentially at rest, their shells of caloric touching. Throughout, Dalton accepts the notion that the only means for the action of forces among atoms is direct contact. He is as uncomfortable with the notion of action at a distance as Newton's contemporaries had been.
c) The total diameter of each particle, including the caloric atmosphere or shell, differs from one substance to the nextDalam teori atom Dalton tidak ada ruang kosong antar atom.
Ruangan antar atom terisi caloric, sesuatu yang mengisi ruang dan berkaitan dengan gejala-gejala yang menyangkut panas.Perumusan Atom Dalton dalam bahasa modern
a) Matter consists of indivisible atoms.
b) Atoms are unchangeable.
c ) Compounds are made of molecules.
d) All atoms or molecules of a pure substance are identically alike.
e) In chemical reactions, atoms are only rearranged, not created or destroyed.Fakta :
No matter in which locality a
pure substance-say a metallic oxide, a drop of
some liquid, or a complex gas-is found, no
matter whether it is artificially prepared or taken
from a natural source, the proportions by weight
of the constituent elements in every case are
always the same.

 Hukum Ketetapan Proporsi :
In forming molecules during chemical
reactions, the numbers of combining atoms
of the different elements form simple, definite
ratios.
No matter in which locality a pure substance-say a metallic oxide, a drop of some liquid, or a complex gas-is found, no matter whether it is artificially prepared or taken from a natural source, the proportions by weight of the constituent elements in every case are always the same.
 Hukum Ketetapan Proporsi :
In forming molecules during chemical reactions, the numbers of combining atoms of the different elements form simple, definite ratios.Kontribusi Dalton :
a) As we saw, Dalton's chemical atom is the concept
that gives physical meaning to the law of
conservation of mass, and that integrates it with
the law of definite proportions.

b) Perhaps the best support of the atomic theory,
by common consent at the time, was an extraordinarily
powerful insight for the later progress
of chemistry. Terutama dalam pengembangan notasi untuk reaksi kimia yang merupakan hal yang sangat penting {indispensable] bagi perkembangan kimia sampai saat ini.
a) As we saw, Dalton's chemical atom is the concept that gives physical meaning to the law of
conservation of mass conservation of mass, and that integrates it with the law of definite proportions.
b) Perhaps the best support of the atomic theory, by common consent at the time, was an extraordinarily powerful insight for the later progress of chemistry. Terutama dalam pengembangan notasi untuk reaksi kimia yang merupakan hal yang sangat penting {indispensable] bagi perkembangan kimia sampai saat ini.
Setelah mengalami pengembangan oleh berbagai ilmuwan lain, misalnya Gay-Lussac, maka Teori Atom mendapatkan bentuknya seperti yang sekarang, terutama dalam model gas, berkat gagasan dari Avogadro.a) As had been often and persistently suggested by Gay-Lussac and others, Dalton's picture of a gas in which the particles are in contact is now replaced by another (it does not matter at this point whether a static or a kinetic model), in which the particles have only a very thin shell of caloric and are quite small compared with the distances between them.
Dalton : Atom-atom saling bersinggungan, harus selalu kontak satu sama lain.Avogadro : Atom-atom ukurannya sangat kecil dibandingkan jaraknya satu sama lain. Antar atom adalah ruang kosong.
b) Contrary to initial considerations of simplicity, or to the firm faith of Dalton, or, in fact, to every reasonable expectation at the time,

the ultimate particles of gaseous elements are conceived to be not necessarily just single solitary atoms, but instead may be thought of as being made up of two or more chemically alike atoms "united by attraction to form a single whole. " Calling the smallest such unit a molecule  - - - - >  munculnya konsep molekulHukum Avogadro :

Equal volumes
of all gases, whether elements or compounds,
or even mixtures, contain equal numbers
of molecules.

Satu mol sembarang gas volumenya sama dan mengandung cacah molekul atau atom yang sama.
Volume = 22,4 liter
Bilangan = NA (Bilangan Avogadro, ordenya 10^23)


Avogadro was not the first scientist to propose
it, but he did succeed in incorporating it into a
coherent and convincing theory.
Equal volumes of all gases, whether elements or compounds, or even mixtures, contain equal numbers of molecules.

Satu mol sembarang gas volumenya sama dan mengandung cacah molekul atau atom yang sama. Volume = 22,4 liter Bilangan = NA (Bilangan Avogadro, ordenya 10^23)

Avogadro was not the first scientist to propose it, but he did succeed in incorporating it into a coherent and convincing theory.b) He replaced the static model, in which atoms are in contact and fill up all the available space, with another model in which the molecules (possibly containing two or more atoms) are quite small compared to the spaces between them.
Avogadro mengubah model statik dari Dalton menjadi bentuk model atom dari gas seperti yang sekarang.
Experiments in many separate branches of physical science since that time have indirectly produced values, and they all agree fairly well on about 2.69 x 10^19 molecules/ cm^3 of any gas at O°C and atmospheric pressure.

As will be noted in Section 22.7, this is now called Loschmidt's number in honor of the scientist whose work led to the first accurate estimate of its value.
Bedakan bilangan Avogadro dengan bilangan Loschmidt, meskipun keduanya merujuk hal yang sama. Bedanya adalah faktor 22.4*10^4. Jelaskan faktor itu !
Inilah definisi satu mol :
A more useful number is the number of
molecules whose mass in grams is the same as
the weight of one of those molecules relative to
the hydrogen atom-for example, the number
of molecules in a 32-gram sample of pure oxygen,
if the molecular weight of oxygen is 32.

This quantity is called the "mole “.
Avogadro's hypothesis states that the number
of molecules in a mole is the same for any
gas, and this number is therefore called Avogadro's
number, even though he did not know
its value.
Bil. Avogadro tidak ditemukan Avogadro, sedangkan bil. Loschmidt memang ditemukan dia.
A more useful number is the number of molecules whose mass in grams is the same as the weight of one of those molecules relative to the hydrogen atom-for example, the number of molecules in a 32-gram sample of pure oxygen, if the molecular weight of oxygen is 32.
This quantity is called the "mole “.
Avogadro's hypothesis states that the number of molecules in a mole is the same for any gas, and this number is therefore called Avogadro's number, even though he did not know
its value.
its value.Bil. Avogadro tidak ditemukan Avogadro, sedangkan bil. Loschmidt memang ditemukan dia.Rangkuman
Kita sudah membahas Teori Atom pertama yg komprehensif yaitu dari Dalton dan perubahannya sampai jadi bentuknya yg seperti sekarang oleh Avogadro dan bagaimana Teori Atom itu bisa menjadi paradigma karena diperlukan bagi tumbuhnya ilmu kimia sehingga memisahkan diri dari natural philosophy.