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Elements and the cell
Elements and the cell
Elements and the cell
Elements and the cell
Elements and the cell
Elements and the cell
Elements and the cell
Elements and the cell
Elements and the cell
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Elements and the cell

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  • 1. Ch.2 “Chemical Context of Life”
  • 2. Concept 2.1: Matter consists of chemical elements in pure form and in combinations called compounds • Matter – “anything that takes up space and has mass” – 3 Forms • Solid • Liquid • Gas – Composed of elements
  • 3. • Element – A substance that cannot be broken down to other substances by chemical reactions – Composed of atoms • Atom: smallest component of an element, contains nucleus of neutrons and protons, and electron cloud
  • 4. • Compound – A substance consisting of two or more different elements combined in a fixed ratio. • Example: NaCl (table salt) – 1:1 ratio of Sodium (Na) to Chloride (Cl) • Example: H20 (water) – 2:1 ratio of Hydrogen (H) to Oxygen (O)
  • 5. Elements-Table 2.1 • 92 Natural Elements (118 total) – Essential elements: 20-25% of natural elements are needed by organisms to live a healthy life and reproduce. • Vary amongst organisms • 4 elements: Oxygen, Carbon, Hydrogen, and Nitrogen (96%) • Remaining elements: Calcium, Phosphorus, Potassium, etc. – Trace elements: required by an organism in small quantities • Iron (Fe) needed by all forms of life, others only needed by certain organisms
  • 6. Concept 2.2: An element’s properties depend on the structure of its atoms • Atom: smallest unit of matter that still retains the property of an element (no chemical change) • Subatomic particles: form the atom – Neutrons (neutral), protons (+), and electrons (-)
  • 7. Figure 2.5 Cloud of negative charge (2 electrons) Electrons Nucleus (a) (b)
  • 8. • Neutrons=Protons= ~1.7x10-24 g • Very small unit to measure – Assigned term “Dalton” – Neutron=Proton=1 Dalton – Electron=1/2000 Dalton **Not used when calculating atomic mass because it’s so small**
  • 9. Atomic Number and Atomic Mass • Atomic number: number of protons – Unique to each element – Charge is considered neutral on each atom – Number of protons=number of electrons • Mass number: sum of neutrons and protons in the nucleus of the atom. ~22.99

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