Chapter 2 Notes.docx - Chapter 2 A chemical connection to...

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Chapter 2 A chemical connection to biology Living organisms are subject to basic laws of physics and chemistry Elements and compounds Ex. Sodium + Chlorine gives NACL Of 92 natural elements, about 20–25% are essential elements , needed by an organism to live a healthy life and reproduce Trace elements are required in only minute quantities For example, in vertebrates, iodine (I) is required for normal activity of the thyroid gland In humans, an iodine deficiency can cause goiter Concept 2.2: An element’s properties depend on the structure of its atoms Each element consists of a certain type of atom, different from the atoms of any other element An atom is the smallest unit of matter that still retains the properties of an element Subatomic Particles Atoms are composed of smaller parts called subatomic particles Relevant subatomic particles include Neutrons (no electrical charge) Protons (positive charge) Electrons (negative charge) Neutrons and protons form the atomic nucleus Electrons form a “cloud” around the nucleus Neutron mass and proton mass are almost identical and are measured in daltons Isotopes All atoms of an element have the same number of protons but may differ in number of neutrons Isotopes are two atomic forms of an element that differ in number of neutrons Radioactive isotopes decay spontaneously, giving off particles and energy The energy levels of Electrons Energy is the capacity to cause change Potential energy is the energy that matter has because of its location or structure The electrons of an atom have potential energy due to their distance from the nucleus Changes in potential energy occur in steps of fixed amounts An electron’s energy level is correlated with its average distance from the nucleus Electrons are found in different electron shells , each with a characteristic average distance from the nucleus The energy level of each shell increases with distance from the nucleus Electrons can move to higher or lower shells by absorbing or releasing energy, respectively See figure 2.5 See figure 2.6 Covalent Bonds
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  • Fall '17
  • MESIA STEED
  • Atom,  Trace elements

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