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KEY CONCEPT All living things are based on atoms and their interactions.

Learn about atoms, elements, compounds, and isotopes - the fundamental units that make up all living things. Understand the importance of covalent and ionic bonds in chemical interactions. Discover the most abundant elements in the human body.

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KEY CONCEPT All living things are based on atoms and their interactions.

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  1. KEY CONCEPTAll living things are based on atoms and their interactions.

  2. Oxygen atom (O) outermost energy level: 6 electrons (-) Nucleus:8 protons (+)8 neutrons inner energy level: 2 electrons (-) • An atom –smallest basic unit of matter Contains: a. nucleus has protons and neutrons. b. electrons are in energy levels – regions around the nucleus.

  3. Elements • Matter that has atoms that are all alike are elements. • Elements cannot be broken down into smaller substances. • Elements are listed on the Periodic Table. • More than 90% of the human body is made of only carbon, hydrogen, oxygen, and nitrogen.

  4. Most abundant elements • The most common elements found in living things are Carbon, Hydrogen, Nitrogen, and Oxygen. • Oxygen, at 65%, is the element that makes up most mass in the human body. • Carbon follows with 18.5%, then hydrogen with 9.5%, and then nitrogen with 3.3%.

  5. H O Living things consist of atoms of different elements. • An atom is the smallest basic unit of matter. • An element is one type of atom. Hydrogen atom (H) Oxygen atom (O)

  6. _ O H H + + • A compound is made of atoms of different elements bonded together. • water (H2O)

  7. A compound is made of atoms of different elements bonded together. • carbon dioxide (CO2) • Glucose • water (H2O)

  8. gained electron Na loses anelectron to CI ionic bond Sodium atom (Na) Chlorine atom (CI) Sodium ion (Na+) Chloride ion (CI-) • An ion forms when an atom gains or loses one or more electrons. • positive ions -formed when atoms lose electrons • negative ions -formed when atoms gain electrons • Ionic bonds –chemical force due to electircal attraction between oppositely charged ions.

  9. covalent bonds Oxygen atom (O) Carbon atom (C) Oxygen atom (O) Carbon dioxide (CO2 ) • Molecules- atoms bonded together by covalent bonds Covalent bonds form when atoms SHARE electrons in their outer energy level. This allows both atoms to become full and stable.

  10. Covalent bonds • Most organic (coming from living things) compounds have covalent bonds. • This includes sugars, fats, proteins, and water.

  11. Compounds you need to know: H2O = water CO2 = carbon dioxide C6H12O6 = sugar (usually glucose) NaCl = table salt NH3 = ammonia

  12. Isotopes • Atoms with the same number of protons and electrons but different numbers of neutrons are called isotopes. • Isotopes have the same element, but may have different properties because of their different masses that may change its stability. • Isotopes are named by adding the number of protons and neutrons. • Some isotopes are useful in telling the age of fossils.

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