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Bonding. Biology Chapter 3. How come Elements bond?. Dot diagrams show that elements want to have their outer electron clouds filled with 8 electrons (except for Hydrogen and Helium: 2 electrons) Chemically stable : outer energy level completely filled with electrons
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Bonding Biology Chapter 3
How come Elements bond? • Dot diagrams show that elements want to have their outer electron clouds filled with 8 electrons (except for Hydrogen and Helium: 2 electrons) • Chemically stable: outer energy level completely filled with electrons • Elements will interact with other elements to fill these electron clouds • Interactions are called chemical bonding
Chemical Bonding • Atoms will find other atoms that will contribute electrons (giving, taking, sharing) in order to fill electron cloud and become stable. • Chlorine has 7 electrons, needs 1 to fill it up to 8 and become stable • Interacts with a Sodium atom that has 1 electron in its outer shell and takes it • Chemical bond!
Chemical Bonding • Chemical Bond: Force that holds together the atoms in a substance. • Ex: NaCl (table salt)
Chemical Bonding • More examples:
Dot diagrams and Periodic table • Periodic table shows number of bonds atoms can make
How do these chemicals bond? • Draw the dot diagram reactions of these elements: • 1 H atom and 1 Cl atom • 2 H atoms and 1 O atom • 2 Cl atoms and 1 Mg atoms • 1 N atom and 3 H atoms • 1 C atom and 2 O atoms
Ionic Bonding Sodium atom (Na) Chlorine atom (Cl) Sodium ion (Na+) Chloride ion (Cl-) Transfer of electron Protons +11 Electrons -11 Charge 0 Protons +17 Electrons -17 Charge 0 Protons +11 Electrons -10 Charge +1 Protons +17 Electrons -18 Charge -1
What’s so special about Gatorade? • http://www.gatorade.com/?bmk=3.5.tour • Electrolytes: used in the nervous system in the body to send signals to muscles. • Electrolytes are an example of ions
What is an ion? • Ion: Atom that is positively or negatively charged • Ex: Na+, Cl-, Mg2+ • Superscript tells you what the charge is • Ions are produced when electrons are given or taken away
Covalent Bonding • Remember, covalent bonding is where electrons are shared • Example: H2O • Molecule: Structure resulting from one or more covalent bonds
Chemical Formulas • Chemical formula: tells what elements it contains and the ratio of the atoms of those elements • Ex: NaCl = 1 Na, 1 Cl • Ex: NaOH = 1 Na, 1 O, 1 H • Ex: HCl? 1 H, 1 Cl
Chemical Formulas • Subscript: shows number of atoms in a compound; comes after the atom • Ex: H2O = 2 H, 1 O • Ex: H2SO4 = 2 H, 1 S, 4 O • Ex: NH3? 1 N, 3 H
What are the Ratios? • NaOH? • MgCl2? • C6H12O6? • C2H5OH? • Mg(OH)2?
How many bonds can an atom make? • Dot diagrams tell you how many bonds an atom can and usually makes • Ex: C has 4 dots, needs 4 electrons • 4 bonds • Ex: Oxygen has 6 dots, needs 2 electrons • 2 bonds