Some interesting videos on basic atomic theory

."In other words, while it was claimed atoms of different elements had different weights, no one could figure out what the different weight values were.

More on the atomic force microscope

Modern scholarship has identified four basic ideas in Dalton's chemical atomic theory.

in which Z is the atomic number and N is the .

On the 23rd of October the same year[I r]ead my at the conclusion of which a series of atomic [weights] was given for 21 simple and compound elements ..

Atomic weights (relative atomic masses) of the first ten elements

"It was not until 1805 that the above essay was published and it was not until 1808 that Dalton himself discussed his methods for atomic weight determination.

These atoms maintain their identity through all physical and chemical changes.

The K, L, M Principle Quantum Number atomic anthropology war reports.

What single parameter uniquely characterizes the atom of a given element? It is not the atom's relative mass, as we will see in the section on isotopes below. It is, rather, the number of protons in the nucleus, which we call the and denote by the symbol Z. Each proton carries an electric charge of +1, so the atomic number also specifies the electric charge of the nucleus. In the neutral atom, the Z within the nucleus are balanced by Z outside it.

The atom was not discovered all at once

Moseley searched for a measurable property of each element that increases linearly with atomic number. He found this in a class of X-rays emitted by an element when it is bombarded with electrons. The frequencies of these X-rays are unique to each element, and they increase uniformly in successive elements. Mosely found that the square roots of these frequencies give a straight line when plotted against Z; this enabled him to sort the elements in order of increasing atomic number.

As technology improves, so does our understanding of the atom

The other nuclear particle is the . As its name implies, this particle carries no electrical charge. Its mass is almost the same as that of the proton. Most nuclei contain roughly equal numbers of neutrons and protons, so we can say that these two particles together account for almost all the mass of the atom.

An element's atoms do not change into other element's atoms by chemical reactions.

Atomic Theory Timeline by Mallory S on Prezi

Earlier experiments had given the composition of water as 87.4 percent oxygen and 12.6 percent hydrogen by weight. This means that if the formula of water is assumed to be HO (as it was at the time — incorrectly), then the mass ratio of the two kinds of atoms must be O:H = 87.4/12.6 = 6.9. Later work corrected this figure to 8, but the wrong assumption about the formula of water would remain to plague chemistry for almost fifty years until studies on gas volumes () proved that water is H2O.

For example, nitrogen and oxygen atoms stay as themselves even when combined.

The Indian Sage who developed Atomic Theory 2,600 …

Because the electrons of an atom are in contact with the outside world, it is possible for one or more electrons to be lost, or some new ones to be added. The resulting electrically-charged atom is called an .

This created the initial conversations on what an atom happened to be with exact definitions.

Atomic - definition of atomic by The Free Dictionary

You can think of the atomic number as a kind of serial number of an element, commencing at 1 for hydrogen and increasing by one for each successive element. The chemical name of the element and its symbol are uniquely tied to the atomic number; thus the symbol "Sr" stands for strontium, whose atoms all have Z = 38.