Atoms

Using indirect information we can infer the identity and the quality of the hidden parts of a model.

Dalton's atomic theory states:

• All elements are composed of atoms.


• atoms of each element are exactly alike but different than atoms of different elements.


• Compounds are formed by joining of atoms of two or more elements.

The negatively charged particles discovered by Thomson are called electrons.

Rutherford has concluded that the nuclues is surrounded by negatively charged electrons, but most of the atom is actually empty space.

Bohr proposed that electrons move around the nucleus in well-defined circular paths(orbit) called energy levels.

Atomic number (Z) is the number of protons in the nucleus of the atom.

Msss number (A) is the number of nucleons of the nuclues of the atom.

Isotops are atoms of the same element that thave different numbers of nuetrons in their nulei.

Atomic mass is expressed in atomic mass units, its symbol is U or Amu.

The mole is the unit (abbreviated mol), used to measure the amount of substance.

One mole atom of an element conatins exactly Na atoms of this element.

Source of the photo: Spectroscopy: A Key Part of the Astronomer's Toolbox (http://ircamera.as.arizona.edu/NatSci102/NatSci102/lectures/spectroscopy.htm)