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Transcript of ATOMIC Models
2. All atoms of an element are identical in properties such as size and mass.
3. Atoms of different elements have different properties.
4. Atoms of different elements can combine in specific ratios to form new substances (compounds!!) J.J. Thompson "Raisin Bun Model" English physicist who discovered the electron.
*All atoms are made of smaller subatomic particles put together in different combinations to make different elements.
He suggested that an atom was a shpere of positive charge in which negative charges were embedded.
The negatively charged particles were called ELECTRONS Ernest Rutherford "Planetary Model" He suggested that an atom is mainly empty space through which the positive particles could pass...
...But, that each atom had a tiny positively charged core.
He called the small dense, positively charged core, the nucleus.
The negatively charged electrons are attracted to the nucleus and orbit in a cloud around it.
Niels Bohr "Bohr Model" Applied his own theories to Rutherford's model.
Bohr, proposed that electrons surrounded the nucleus in specific energy levels.
His evidence came from: examining the light released by hydrogen (H) atoms when they are made to glow in a tube.
The individual bands of light correspond to gaps between the energy levels of the electrons.
When electrons fall from higher energy levels to lower energy levels, they release a particular color of light.
From the colors it is possible to identify the energy levels of all of the levels in the periodic table.
Electrons cannot fall below the lowest energy level.
Quantum Mechanical Model Today's model is based on a theory called quantum mechanics.
Each electron is thought of as a cloud of negative charge, rather than a tiny negative particle.
The whole idea of electrons orbiting or movement is gone.
Electrons occupy the whole space all at once at different energy levels = Electron Cloud.
The cloud surrounds a nucleus that contains two types of particles: protons and neutrons.
Protons have a positive charge and neutrons have a neutral charge.