This model of the atom is commonly known as the Quantum Mechanical Model or Electron Cloud Model. In philosophy The basic idea that matter is made up of tiny indivisible particles is an old idea that appeared in many ancient cultures. Many scientists contributed to this theory including: It does not explain the shapes of molecules or other abnormalities that result form unevenly shared pairs of electrons (such as the abnormal behaviour of water, the difference in Carbon-Carbon Bonds between diamond and graphite etc.) Places electrons in definite energy levels Relegates the number of valence electrons to the Periods of a periodic tableįully explains ionic and covalent bonding Proposes that the atom is really mostly empty spaceĭoes not place electrons in definite energy levels around the nucleusĭoes Not relate the valence electrons atomic chargeĮlectrons in Definite energy Levels around the nucleus: Used atomic spectra to prove that electrons are placed in definite orbitals (called shells) around the nucleus.Įxplains the role of valence electrons in bonding The Planetary Model: The Famous Gold Leaf Experiment proved that the nucleus is positive and the electrons are outside the nucleus.Įxplains why the electron spins around the nucleus - (Bohr's Contribution) A widely recognized theory in this area is A Theory of Magnitude (AToM), which postulates that a shared neural mechanism processes spatial, temporal, and numerical information (Meck & Church, 1983. Learn about the ancient and modern atomic theories, the scientists who developed them, and the facts that support them. Infers on the relative nuclear density and atom mass of different atomsĭoes not explain the existence of electrons outside the nucleus does not explain the role of electrons in bondingĭoes not talk about neutrons therefore can't explain radioactivity and the existence of isotopes Atomic theory is the scientific theory of matter based on the idea that the chemical elements are composed of aggregations of similar subunits (atoms) with nuclear and electron structure. Infers on the existence of electrons and protons The raisin bun Model or the chocolate chip cookie model: Atoms are solid spheres made-up of a solid positive mass (or core) with tiny negative particles embedded in the positive core. The solid sphere model: Atoms are seen as solid, indestructible spheres (like billiard balls)Įxplains a lot of chemical properties such as how atoms combine to form moleculesĮxplains chemical change better than the Particle TheoryĬonfirms the basic Laws of Chemistry: Conservation of Mass & definite Proportionsĭoes not include the existence of the nucleusĭoes not explain the existence of ions or isotopesĭoes not talk about subatomic particles: (Electrons, Protons, Neutrons) Does not give a scientific view of the atom only a conceptual definitionĭoes not talk about subatomic particles (Electrons, Protons, Neutrons).

The word ‘atom’ actually comes from Ancient Greek and roughly translates as. In fact, we have to go all the way back to Ancient Greece to find its genesis. Though our graphic starts in the 1800s, the idea of atoms was around long before. Talks about the atom as the smallest particle of matter.ĭefines the atom as an indivisible particleĮxplains certain natural occurrences such as the existence of elements This graphic takes a look at the key models proposed for the atom, and how they changed over time. Summarized below are the various atomic models that have been developed during the course of history.Ītom the indivisible particle: Atomos (in ancient Greek) means 'that which cannot be further broken down into smaller pieces' The modern model of the atom is called the Quantum Model and you will study this model in future grades (Grade 11 and 12 Chemistry & Physics). This view of the atom is still a Theory and therefore it is still subject to change. New ideas, and new technologies have influenced the model of the atom.

Throughout the centuries the 'view' of the atom has changed. The idea of an atom - the smallest particle of matter - has intrigued mankind since the beginning of civilization.

Atom theory