Lesson 1: Elements and Atoms

6. Models of Atom

In this course, we will be studying five different models. However, we will be focusing more on the Bohr model and the energy-level diagram. In lesson four, we will revisit the electron cloud model. Study the following two diagrams that demonstrate the same information about phosphorous, then review the models of atom activity.

Electron configurations are as follows for a maximum number of electrons per energy level.

1st energy level: maximum of 2 electrons
2nd energy level: maximum of 8 electrons
3rd and higher energy levels: 8 electrons

How Atoms Combine:
The atoms of elements combine to form millions of different compounds with varying physical and chemical properties. This combining atom is called chemical bonding. Chemical bonds involve the electrons in the outermost energy levels of the reacting atoms. All atoms tend to fill their most outer energy level with electrons to become more stable.
For example, hydrogen atoms have a single electron in the first energy level. Helium atoms have 2 electrons that fill the first and outermost energy level. Hydrogen atoms are highly reactive, helium atoms are highly stable.

Atoms do not combine randomly, they react to lose, gain, or share electrons in order to completely fill the outermost energy level. Atoms can fill their outermost energy levels by the transfer of electrons from one atom to another. One atom gains electrons while the other atom loses electrons. Doing so, no longer neutral, atoms become ions. Ions with opposite charges attract each other. This is how some compounds form.
Models of Atoms:
Try the following activity summarizing the models of atoms.