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CHEMICAL BONDING

CHEMICAL BONDING. Bonding and Energy. Energy is important to making and breaking bonds Building Chemical Bonds can either absorb energy or release energy Exothermic Reactions – Produce energy as light, heat, sound, bubbles, precipitates Mitten warmers, cellular respiration, all combustion

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CHEMICAL BONDING

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  1. CHEMICAL BONDING

  2. Bonding and Energy • Energy is important to making and breaking bonds • Building Chemical Bonds can either absorb energy or release energy • Exothermic Reactions – Produce energy as light, heat, sound, bubbles, precipitates • Mitten warmers, cellular respiration, all combustion • Endothermic Reactions – Absorb energy; make things feel cold, create complex molecules • First aid cold packs, photosynthesis

  3. Valence Electrons Each atom or element has electron in orbits around the nucleus. Valence electrons are the electrons in the outer shell of an atom. Number of valence electrons of a group 1 8 2 3 4 5 6 7 The transition metals have highly variable numbers of valence electrons, ranging from 1-8

  4. Why do atoms bond? • Electrons orbit nucleus in “shells” or “orbitals” • Number of shells increases with the Period or Row on the Periodic Table • H & He have one orbital that can hold 2 electrons • Period 2, starting with Lithium, has two orbitals. The lowest has 2 electrons and the second can hold up to 8 electrons. • The electrons in the outer shell are called valance electrons • Determine the chemical properties of the element. • Number of valence electrons increases from left to right on the Periodic Table. • Atoms "like" to have their outer orbits completely filled with the maximum number of electrons allowed. • Bonding with other atoms helps to fill the outer orbitals.

  5. 3 types of Chemical Bonds • Ionic — complete transfer of 1 or more electrons from one atom to another • A metal loses an electron becoming more positive • A nonmetal gains an electron becoming more negative • forming oppositely charged ions that attract one another (ex NaCl ) • Covalent — Nonmetal atoms share one or more valence electrons. Ex. SiO2 • Metallic — Metal atoms “pool” valence electrons which move amongst the atoms. Ex Au

  6. Ionic Bonds Metal-Nonmetal Metal gives up electron Nonmetal takes electron Crystalline Solids Soluble in water Very high melting points Ex. NaCl or Halite Do NOT conduct electricity except when dissolved in water Salts can be toxic but are also essential…

  7. Sodium gives up its one outer electron to fill the Chlorine’s outer shell

  8. Covalent Bonds • Nonmetal – Nonmetal • Sharing of one or more valence electrons • Examples: O2, N2, CO2, graphite, diamonds, quartz, fats, carbohydrates, DNA, proteins • Variable structures, states, solubility, melting points • Do NOT conduct electricity. • Covalent bonding is the most common type of chemical bonding.

  9. A chlorine atom shares one of its outermost electrons with another chlorine atom.

  10. Metallic Bonds • Metal – Metal • Electrons are pooled amongst atoms • Crystalline solids • Soluble in water • Medium to high melting points • Conduct electricity & heat • Malleable, ductile, reflective. • Ex: Gold, Bronze, Brass, Steel

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