BIOL&251Ch2NotesSpr11

BIOL&251Ch2NotesSpr11 - Chapter 2: The Chemical Level of...

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1 Chapter 2: The Chemical Level of Organization Chemistry = the science of the structure of matter Matter takes up space and has mass (weight) – It can exist as a solid , liquid , or gas • The smallest stable units of matter = atoms , which are made up of… Protons – in the nucleus; positively charged Neutrons – in the nucleus; uncharged Electrons – orbit the nucleus; negatively charged Table 2-1, part 1, p. 30 Atoms are classified into elements by the number of protons they have (= the atomic number ) The info in the table is FYI
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2 Table 2-1, part 2, p. 30 FYI Fig. 2-1, p. 29 Atoms have equal numbers of protons and electrons, so overall they are electrically neutral 2 electrons can orbit in the first energy level (electron shell); 8 electrons each can orbit in all higher-level energy levels The outermost electron shell determines an atom’s reactivity with other atoms (i.e., an atom is stable only if its outermost electron shell is full) The basic structure of atoms
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3 Atoms combine via chemical reactions, forming chemical bonds Molecule = a chemical substance made up of atoms of any elements held together by covalent bonds –E .g . O 2 (oxygen gas), H 2 O (water), C 6 H 12 O 6 (glucose) Compound = a chemical substance made up of atoms of different elements , regardless of bond type – E.g. NaCl (table salt), H 2 O, C 6 H 12 O 6 • Types of bonds : – 1. Ionic bonds – 2. Covalent bonds – 3. Hydrogen bonds Ionic bonds Ion = an atom that carries an electric charge (i.e., it has unequal protons and electrons) Cation = a positively charged ion Anion = a negatively charged ion – Ions play many vital roles in our bodies (e.g. muscle/nerve function, fluid volume, etc.) Ionic bonds
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4 Covalent bonds • Electrons are shared between atoms; this is the strongest bond type Single covalent bond = one pair of electrons are shared Double covalent bond = two pairs of electrons are shared Nonpolar covalent bonds – Electrons are shared equally between atoms Polar covalent bonds – Electrons are shared unequally (see the next slide) Free radical = an ion or molecule with unpaired electrons in its outermost electron shell – These are often unstable, reactive, and destructive Fig. 2-4, p. 34 Fig. 2-5, p. 35 Water: formed by polar covalent bonds • O attracts H’s electrons more strongly than H does – The O becomes slightly/partially negative (–) – Each H becomes slightly/partially positive (+) Water is a polar molecule
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5 Fig. 2-6, p. 36 Hydrogen bonds • H-bonds involve polar covalent bonds that occur when hydrogen covalently bonds with another element (such as in H 2 O) • Partially positive ( δ + ) and negative ( δ - ) charges attract each other • H-bonds are the weakest individual bonds (that we’ll learn about, anyway)
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This note was uploaded on 12/29/2011 for the course BIOLOGY 24011 taught by Professor Pan during the Fall '11 term at HCCS.

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BIOL&251Ch2NotesSpr11 - Chapter 2: The Chemical Level of...

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