1. C HAPTER 4.3 – M ODERN A TOMIC T HEORY

2. T HE B OHR M ODEL OF THE A TOM The Bohr model of the atom is commonly used in science classes to help visualize where electrons are in the electron cloud. This model shows atoms in electron energy levels that orbit around a central nucleus. The level closest to the nucleus has the lowest energy and can only hold two electrons. The energy of these electron levels increases with each added ring present.

3. T HE E LECTRON C LOUD M ODEL OF THE ATOM The modern model of the atom is the electron cloud model. This model shows that electrons exist in a cloud as it is difficult to find the fast moving electron. The exact location of an electron at any given second can not be determined. The dense areas of the cloud show where it is most probable to find an electron.

4. O RBITALS Electrons exist in orbitals in the electron cloud. An orbital is an area outside the nucleus where an electron is likely to be found. Each orbital can hold up to a pair of electrons. This is where we get the maximum numbers of electrons that can exist in each energy level.

5. G ROUND STATE When all electrons in an atom have the lowest possible energies, this is called the ground state for an atom. The ground state is what is shown in the diagrams we made of atoms in class. When electrons absorb energy, we call this the excited state. Atoms in the excited state are less stable (less likely to exist) than in those in the ground state. The reason that neon and many gases glow is that they are giving off energy as light as they return to a ground state from an excited state.