Consider only the nucleus when you are concerned with isotopes. Electrons play no part in isotopes or the atomic mass, Figure 2. Only protons and neutrons contribute to the mass of an isotope.

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Matter: Composition

Matter by Composition   You can describe matter based on composition. This means you describe collections of matter based on what makes it up. The first kind of description refers to whether or not you want to describe a pure substance or mixture.           Pure Substance or Mixture   The components […]

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chemical energy

Chemistry Energy

Energy The idea of energy is abstract and difficult to visualize. You can understand it better from the point that although you cannot measure energy directly, you can measure the effects of energy. The two most common visible effects of energy are work being done or a change in temperature.  Figure 1 shows how coal […]

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