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# The Chemical Level of Organization Chemistry is the science that deals with the structure of matter. * **Matter is defined as anything that takes up space and has mass.** The study of matter and the energy involved in processes that are associated with matter is called *chemistry.* * **Mass is a...

# The Chemical Level of Organization Chemistry is the science that deals with the structure of matter. * **Matter is defined as anything that takes up space and has mass.** The study of matter and the energy involved in processes that are associated with matter is called *chemistry.* * **Mass is a physical property that determines the weight of an object in Earth's gravitational field.** Although sometimes mass and weight are used synonymously, it is important to note that they may not be equivalent. For example, in orbit you would be weightless, but your mass would remain unchanged. * **Atoms are the smallest stable units of matter.** The unique characteristic of any object, living or nonliving, result from the types of atoms involved and the ways those atoms combine and interact. * **Atoms are composed of subatomic particles.** Although a variety of subatomic particles exists, we will only focus on three: 1. Protons 2. Neutrons 3. Electrons Protons and neutrons are similar in size and mass; however, protons bear a positive electrical charge, whereas **neutrons are electrically neutral.** The protons and neutrons are located in the **nucleus of the atom**. Thus, if you were able to take apart an atom and collect the subatomic particles of the nucleus you will have protons and neutrons. **Electrons are much lighter than protons and bear a negative electrical charge.** They are outside orbiting the nucleus. In determining the mass of an atom, we generally ignore the mass of the electrons. Thus, the mass of an atom is therefore determined primarily by the number of protons and neutrons in the nucleus.