Draft:Dalton's atomic model
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Dalton's atomic model
Dalton's main postulates
Dalton formed his
- Matter is formed by very small particles named atoms, these are indivisible and cannot be destroyed.
- Atoms of the same isotopes, whose distinctive characteristic is the number of neutrons in the nucleus, which changes the atomic mass of each of them and physical properties such as their density). Atoms from different elements have different mass (comparing the mass of the elements to the mass of the hydrogen, as a unit, he proposed the concept of atomic weight, although for his lack of knowledge on the existence of isotopes, he really meant what we now know as relative atomic mass, which averages the masses of different isotopes of one same element).
- Atoms are indivisible even when they are combined in chemical reactions.
- moleculesH2O).
- Atoms, when they combine to form compounds, mantain simple numeric relations (for example, in the formation of water, the relation is 2:1, two hydrogen atoms with one oxygen atom).
- Atoms of different elements can combine in different proportions and form more than one compound (for example, the compund made from two hydrogen atoms and one oxygen atom is water H2O; as the compund made from two hydrogen atoms and two oxygen atoms gives a different result known as hydrogen peroxide H2O2, also known as liquid un-bleach).
Model's insufficiencies
John Dalton's hypothesis, that stated elements in gaseous state were
In 1805,
In 1860, in Karlsruhe Congress about stable masses and atomic weights, Cannizzaro revived Avogadro's ideas and used them to elaborate a periodic table regarding relative atomic mass[8] that was very similar to the actual values. These weights were an important sos fueron un importante prerequisite for the discovery of Dmitri Mendeléyev and Lothar Meyer's Periodic Table.
Other limitation of Dalton's original model is that it ignores the existence of different isotopes of a determinated element, when in reality slightly different versions of atoms of each element can exist that differ in number of
Dalton also stated that atoms differentiated according to their size, being hydrogen the smallest one.
Finally, until the last half of the XIX century, no evidence of atoms being divisible or being constituted by more elemental parts appeared.
References
- ISBN 9789684444140. Retrieved 11 December 2015.
- ISBN 9789709758818. Retrieved 11 December 2015.
- ISBN 9789702602811.)
{{cite book}}
: CS1 maint: numeric names: authors list (link - ^ Picado, Ana Beatriz; Álvarez Milton. (2008) Química I. Editor EUNED. p. 108.
- )
- ISBN 9786077440079. Retrieved 3 March 2018.
- ISBN 9788497172110. Retrieved 3 March 2018.
- ISBN 9788429171532. Retrieved 3 March 2018.
- ISBN 9788472453777. Retrieved 3 March 2018.