back arrow   forward arrow

Key Idea 1
Atomic Structure
Concept Question: What is the structure of an atom?

What do we know?

Atoms consist of a central nucleus, containing positively charged protons (m=1.67x10- 27 kg) and neutral neutrons (m=1.67x10- 27 kg), surrounded by negatively charged electrons (m=9.109x10- 31 kg). Protons and neutrons have almost the same mass, which is much larger than the mass of an electron. Therefore, the vast majority of the mass of an atom is contained in the nucleus. However, the outer electrons occupy the majority of the physical space taken up by an atom.oxygen-16 nucleus

Different elements are defined by the number of protons contained in their atoms. The number of protons of a specific element is called the atomic number and is given the symbol, Z. The atomic number of each element is indicated on the periodic table.

Neutral atoms have the same number of protons as electrons. The numbers of protons and electrons govern the many properties of the atom.


How do we know?

Much of our knowledge of atomic structure was discovered through the famous Rutherford experiment. If you would like to learn more about this experiment, work through the following Rutherford learning tool suite.