Early+atomic+models

=​Early atomic models=

@ Textbook
 * []
 * Theory and traditional thinking about atomic models**
 * Things we know now **



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The atoms models of the Early Greeks were thought as the **matters had no properties itself,** and many kinds of simple properties get together existed in this undifferentiated "matter"to creat every substance known.The four properties which could exist were moist, dry, heat and cold.Thus, the four majoy elements were contained water, air, fire and earth.=====
 * AIR** moist **WATER**

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__Dalton's theory was based on** the premise that the atoms of different elements could be distinguished by differences in their weights .** He stated his theory in a lecture to the Royal Institution in 1803.__ The theory include:=====
 * 1) **All elwments is composed of extremely small particles which called atoms.**
 * 2) **Atoms cannot be made or destroyed.**
 * 3) **All atoms of the same element are identical.**
 * 4) **Different elements have different types of atoms,it means they have different properties.**
 * 5) **Chemical reactions occur when atoms are rearranged.**
 * 6) **Compounds are formed from atoms of the constituent elements, each compound is unique of particular combination of atoms.**

Using his theory, Dalton rationalised the various laws of chemical combination which were in existence at that time. @**The Law of Definite Proportions**: Every pure sample of a particular compound always contains the same proportion by mass of the elements in the compound.(3 & 6) @**The Law of Multiple Proportions**: When different masses of one element combine with a specific mass of a second element, the mass ratios of the first element are small whole number ratios.(6) @**The Law of Conservation of Mass**:The mass of the reactants equals the mass of the products.(4)

However, he made some **mistakes**. Today we know that ** atoms can be destroyed into nuclear and electrons, nuclear also can be divided into protons and neutrons.Atoms can have reactions without chemical reactions. Also, there are different kinds of atoms within an element that are known as "isotopes", but isotopes of an element have the same chemical properties.

The Thomson Model of the Atom ** Analogy: The atom is a like a **plum pudding**
 * **The whole pudding is an atom representing the ball of positive charge.**
 * **The pluns are electrons which spreads which out in the atom.**

Today, we know that Thomson's model was wrong :
 * Atoms must possess charge might exist.It is a sphere like jujube cake, positive charge distributed throughout inside of the ball , and electronic as the dates inlaid in that cake of jujube**.
 * **The atom include protons, neutions and electrons.**
 * **Protons are scattered throughout the atom ratter than in the centre.**
 * **Electrons are outside of the nucleus.**

Although the Thomson model was later disproved, it was consistent with the data available at the time and represented an elegant model having a great deal of explaining power. He discovered the mass to charge ratio of an electron:
 * ** e/m=－1.76×10 8 coulombs/gram **