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Chemistry LibreTexts

2: Elements and Ions

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  • Chemistry is the study of matter and the changes it undergoes. Atoms are the building blocks of matter and are the smallest unit of an element.

    • 2.1: Isotopes and Atomic Mass
      Atoms are the fundamental building blocks of all matter and are composed of protons, neutrons, and electrons. Isotopes are atoms of the same element with a different mass due to a different number of neutrons.
    • 2.2: Matter
      Living things are made of matter. In fact, matter is the "stuff" of which all things are made (see figure below. Anything that occupies space and has mass is known as matter. Matter, in turn, consists of chemical substances. Chemistry is the study of matter and the changes it undergoes.
    • 2.3: Mole and Molar Mass
      A mole is used as a measure of the amount of substance present.  Atoms are very small so using more common counting numbers, such as a dozen, are impractical.
    • 2.4: Electron Arrangements
      The number and arrangement of electrons in an atom control the types and number of bonds that an atom can form so understanding their arrangement helps explain the behavior of an atom in a compound or molecule.
    • 2.5: Ion Formation
      Ions form from the gain or loss of electrons.  The electron arrangements allows for the prediction of how many electrons will be gained or lost.
    • 2.6: Ionic Compounds
      Ionic compounds form from at least one negatively-charged anion and one positively charged cation.  The charges on the ions allow the prediction of the number of each that are combined to form a single formula unit of an ionic compound.
    • 2.7: Elements and Ions (Exercises)
      These are homework exercises to accompany Chapter 2 of the University of Kentucky's LibreText for CHE 103 - Chemistry for Allied Health. Solutions are available below the questions.