Dalton's Atomic Theory | Modifications simplified #Atomic theory
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DALTON'S ATOMIC THEORY-------------------------------------------------
DALTON'S ATOMIC THEORY
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00:00 - [ DALTON'S ATOMIC THEORY ]
01:36 - [ MODIFICATIONS OF DALTON'S ATOMIC THEORY]
06:00 - [ MODERN ATOMIC THEORY ]
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The idea that elements are made from atoms is termed the Atomic theory. In 1808, John Dalton presented his famous atomic theory which states as follows:
a. All elements are made from small indivisible particles called atoms.
b. Atoms cannot be created or destroyed.
c. Atoms of the same elements are exactly alike in every aspect and are different from atoms of all other elements.
d. Atoms of different elements can combine in simple whole numbers ratios to form compounds.
e. All chemical changes result from the combination or the separation of atoms.
Most of Dalton's atomic theory is still accepted, but some of the details have been modified due to modern discovery, although, the key aspects as outlined are still useful in the study of chemistry.
MODIFICATION OF DALTON'S ATOMIC THEORY
1. All elements are made up of small indivisible particles called atoms: The atomic nature of elements is not disputed. Atoms can, however, no longer be regarded as indivisible because according to Rutherford's discovery, an atom is made up of three main subatomic particles called protons, neutrons and electrons.
2. Atoms cannot be created or destroyed
This statement is still acceptable for ordinary chemical reactions. The changes associated with nuclear fission, destroy atoms of the element involved, in the sense that the nuclei are broken into smaller units which correspond to simpler atoms.
e.g., the nucleus of uranium -235, can absorb a neutron and then break up into two unequal fragments which form simpler atoms, while a large amount of heat energy is released.
3. Atoms of identical elements are alike in every aspect and differ from atoms of all other elements: the knowledge of isotopes contradicts this statement. Chlorine, for example, has isotopes 35 Cl, 37 Cl and both have 17 nuclear protons and 17 electrons arranged 2, 8, 7, so they have the same atomic number and chemical properties. But the 37 Isotope has two extra neutrons in the nucleus, hence it is heavier, i.e., they have different atomic masses.
4. Atoms of different elements combine in simple whole-number ratios to form compound: This statement is still acceptable for inorganic compounds which usually contain few atoms per molecule. Carbon, however, forms very large organic compounds such as proteins, fats and starch which contain thousands of atoms. Silicon, which is inorganic, also forms some very complex trioxosilicates (IV) involving a large number of atoms.
THE MODERN ATOMIC THEORY
The modified Dalton's atomic theory is also called the modern atomic theory and consists of subsequent features:
a. All matter is composed of small particles, some of which are electrically neutral, some are positively charged while some are negatively charged.
b. Atoms of the same element are not alike but may have different masses.
c. An element may have atoms with different masses. These atoms of an identical element with different masses are called Isotopes.
d. Atoms of different elements can combine together to form molecules
e. Molecules are the smallest particles of compounds that have the properties of the compound.
f. Molecules may be further broken down and when this happens, they no longer have the characteristics of the compound.
g. The molecules of a compound consists of the atoms of the elements that form the molecules.
h. The molecules of a compound have definite compositions and structures.
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-------------------------------------------------
00:00 - [ DALTON'S ATOMIC THEORY ]
01:36 - [ MODIFICATIONS OF DALTON'S ATOMIC THEORY]
06:00 - [ MODERN ATOMIC THEORY ]
-------------------------------------------------
The idea that elements are made from atoms is termed the Atomic theory. In 1808, John Dalton presented his famous atomic theory which states as follows:
a. All elements are made from small indivisible particles called atoms.
b. Atoms cannot be created or destroyed.
c. Atoms of the same elements are exactly alike in every aspect and are different from atoms of all other elements.
d. Atoms of different elements can combine in simple whole numbers ratios to form compounds.
e. All chemical changes result from the combination or the separation of atoms.
Most of Dalton's atomic theory is still accepted, but some of the details have been modified due to modern discovery, although, the key aspects as outlined are still useful in the study of chemistry.
MODIFICATION OF DALTON'S ATOMIC THEORY
1. All elements are made up of small indivisible particles called atoms: The atomic nature of elements is not disputed. Atoms can, however, no longer be regarded as indivisible because according to Rutherford's discovery, an atom is made up of three main subatomic particles called protons, neutrons and electrons.
2. Atoms cannot be created or destroyed
This statement is still acceptable for ordinary chemical reactions. The changes associated with nuclear fission, destroy atoms of the element involved, in the sense that the nuclei are broken into smaller units which correspond to simpler atoms.
e.g., the nucleus of uranium -235, can absorb a neutron and then break up into two unequal fragments which form simpler atoms, while a large amount of heat energy is released.
3. Atoms of identical elements are alike in every aspect and differ from atoms of all other elements: the knowledge of isotopes contradicts this statement. Chlorine, for example, has isotopes 35 Cl, 37 Cl and both have 17 nuclear protons and 17 electrons arranged 2, 8, 7, so they have the same atomic number and chemical properties. But the 37 Isotope has two extra neutrons in the nucleus, hence it is heavier, i.e., they have different atomic masses.
4. Atoms of different elements combine in simple whole-number ratios to form compound: This statement is still acceptable for inorganic compounds which usually contain few atoms per molecule. Carbon, however, forms very large organic compounds such as proteins, fats and starch which contain thousands of atoms. Silicon, which is inorganic, also forms some very complex trioxosilicates (IV) involving a large number of atoms.
THE MODERN ATOMIC THEORY
The modified Dalton's atomic theory is also called the modern atomic theory and consists of subsequent features:
a. All matter is composed of small particles, some of which are electrically neutral, some are positively charged while some are negatively charged.
b. Atoms of the same element are not alike but may have different masses.
c. An element may have atoms with different masses. These atoms of an identical element with different masses are called Isotopes.
d. Atoms of different elements can combine together to form molecules
e. Molecules are the smallest particles of compounds that have the properties of the compound.
f. Molecules may be further broken down and when this happens, they no longer have the characteristics of the compound.
g. The molecules of a compound consists of the atoms of the elements that form the molecules.
h. The molecules of a compound have definite compositions and structures.
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Facebook: lrntube
#Dalton'satomictheory, #atomictheory
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