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What is a chemical bond - Briefly explain two types
An electrical force of attraction between atoms to form molecules. Ionic- completely transfered; Covalent- shared electrons
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Why do atoms bond?
- To become isoelectronic to the inert gases...
- Why the inert gases?
Because they are chemically stable... - How do we know the inert gases are stable? They dont chemically combine, high IE, 0 electron affinity, no electronegativity...
- What makes them stable? 8 valence electrons
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Explain in detail an ionic bond
- Na1 >> Cl7
- 1) Energy is supplied - sodium loses an electron (Na has a low ionization energy)
- 2) Na is now a cation - Na+1 (also isoelectronic to neon)
- 3) Free electron goes to chlorine- Cl has a high electron affinity
- 4) Cl is now an anion - Cl-1 (also isoelectronic to argon
- 5)Opposite ions attract
- 6) Electron stays with Cl - Cl has a high electron negativity
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Changes in ionic bond for different elements
- For some elements there is not a 1:1 ratio
- Na 1>>> O 6 Na2O
- Na 1>>>>^
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Ionization Energy - def. trends, why, highest and lowest 1st and 2nd
- Definition- The energy required to remove an electron from an atom
- Trends and why- increase up (shielding effect) and increase across (closer to 8 valence electrons)
- Highest IE- 1st: He 2nd: Li+1
- Lowest IE- 1st: Fr 2nd Ra+1
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Electronegativity- def. trends, why, highest and lowest 1st and 2nd
- Definition- Attraction for electrons after it has bonded
- Trends increase up (shielding effect) increase left (close to the stable 8) and none for noble gases (they don't form compounds)
- Highest 1st: Flourine 2nd: Oxygen
- Lowest 1st: inert gases 2nd: Francium
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Electrolyte- why important in the body
A substance that in dissolved or molten form conducts electricity. They help send signals throughout the body
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Three definitions of valence
- 1)A number telling the combining capacity of an element
- 2)The # of valence electrons in excess are lacking from the stable set of 8
- 3) The charge in the ion after losing or gaining electrons
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Explain with sample - pure, polar, double, triple covalent bond (lewis dot diagram)
- Pure- share the electrons equally
- Polar- electrons are not shared equally
- Double and Triple- Atoms share 2 (or 3) pair of valence electrons H-C=C-H
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Hybrid orbital - show example
- A mixture of orbitals formed during a covalent bond
- H H
- H-C-C-H
- H H
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Properties of ionic and covalent compounds
- Ionic- (1) White (2) Crystalline (3) Solid (4) High m.p. (5)High b.p. (6) dissolves in water (7) electrolyte
- Covalent- (1) Any state (2) Any color (3) Low m.p. (4) Low b.p. (5) non-soluble (6) non-electrolyte
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Define hydrocarbon, unsaturated, dipole moment, shielding effect
- Hydrocarbon- Contains hydrogen and carbon
- Unsaturated- has at least one double or triple covalent bond
- Dipole moment- a measure of the charge distribution of a dipole
- Shielding effect- inner electrons blocking the valence electrons from the nucleus
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