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Chemistry LibreTexts

1: Matter, Atoms, and Elements

  • Page ID
    290486
    • 1.1: Prelude to Chemistry, Matter, and Measurement
      Quantities and measurements are as important in our everyday lives as they are in medicine. The posted speed limits on roads and highways, such as 55 miles per hour (mph), are quantities we might encounter all the time. Both parts of a quantity, the amount (55) and the unit (mph), must be properly communicated to prevent potential problems. In chemistry, as in any technical endeavor, the proper expression of quantities is a necessary fundamental skill.
    • 1.2: What is Chemistry?
      Chemistry is the study of matter—what it consists of, what its properties are, and how it changes. Being able to describe the ingredients in a cake and how they change when the cake is baked is called chemistry. Matter is anything that has mass and takes up space—that is, anything that is physically real.
    • 1.3: The Classification of Matter
      Matter can be described with both physical properties and chemical properties. Matter can be identified as an element, a compound, or a mixture.
    • 1.4: Measurements
      Chemists measure the properties of matter and express these measurements as quantities. A quantity is an amount of something and consists of a number and a unit. The number tells us how many (or how much), and the unit tells us what the scale of measurement is. For example, when a distance is reported as “5 kilometers,” we know that the quantity has been expressed in units of kilometers and that the number of kilometers is 5.
    • 1.5: Temperature Units and Conversions
    • 1.6: The Elements
      All matter is composed of elements. Chemical elements are represented by a one- or two-letter symbol.
    • 1.7: Atomic Theory
      Atoms are the ultimate building blocks of all matter. The modern atomic theory establishes the concepts of atoms and how they compose matter.
    • 1.8: The Structure of Atoms
      Atoms are composed of three main subatomic particles: protons, neutrons, and electrons. Protons and neutrons are grouped together in the nucleus of an atom, while electrons orbit about the nucleus.
    • 1.9: Nuclei of Atoms
      Elements can be identified by their atomic number and mass number. Isotopes are atoms of the same element that have different masses.
    • 1.10: Uses of Radioactive Isotopes
      Radioactivity has several practical applications, including tracers, medical applications, dating once-living objects, and preservation of food.
    • 1.11: Atomic Masses
      Atoms have a mass that is based largely on the number of protons and neutrons in their nucleus.
    • 1.12: The Periodic Table
      The chemical elements are arranged in a chart called the periodic table. Some characteristics of the elements are related to their position on the periodic table.
    • 1.13: Chapter 1 Exercises

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