Chapter_08-Bonds

Chapter_08-Bonds - Chapter 8. Bonds Chapter Chemical bonds...

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Chapter 8. Bonds Chapter 8. Bonds Chemical bonds 1.Ionic bonds 2.Covalent bonds 3.Metallic bonds Extreme cases In reality, chemical bonds are something in between these three extremes. Chemical bonds are force connections between atoms which holds atoms together.
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Chapter 8. Bonds Chapter 8. Bonds Ionic bonds An electron completely moves from one atom to another. It is basically electrostatic attraction between cation and anion. Usually formed between typical metals and typical non- metals (e.g. alkali metals and halogens). In disscosiation/reconstition ions change their neighbors.
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Chapter 8. Bonds Chapter 8. Bonds Covalent bonds Electrons are shared by two atoms. Usually formed between non-metals (e.g. two fluorine atoms). Atoms stay together until molecule is destroyed (exception – dissociating hydrogen in weak organic acids)
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Chapter 8. Bonds Chapter 8. Bonds Metallic bonds Many electrons are shared by all atoms of metallic object. Electrons are relatively free and form “electron gas” resulting in high electric conductivity.
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Chapter 8. Bonds Chapter 8. Bonds Lewis symbol - Shows the outer electrons as dots around the symbol of element. - Dots can be placed at any side of the symbol. - Unpaired electrons are shown by one dot, paired – by two. The octet rule : atoms tend to gain, lose or share electrons until they are surrounded by eight valence electrons (exception: transition metals).
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Chapter 8. Bonds Chapter 8. Bonds Ionic bonding Sodium: typical element with low ionization energy Chlorine: typical element with high electron affinity
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Chapter 8. Bonds Chapter 8. Bonds Ionic bond forming is exothermic reaction. Na(s) Na(g) H = 108 kJ/mol 1/2Cl 2 ( g ) Cl( g ) H ~ 100 kJ/mol Na( g ) Na + ( g ) + e - H = 496 kJ/mol Cl( g ) + e - Cl - ( g ) H = -349 kJ/mol Na + ( g ) + Cl - ( g ) NaCl( s ) H = -788 kJ/mol (lattice energy) ------------------------------------------------------------- 1/2Cl ( g ) + Na(s) H ~ - 433 kJ/mol Ionic compounds are usually brittle crystals with high melting point.
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Chapter 8. Bonds d - elements Atom starts to use electron always from s -subshell (if there are any), and only then – from d -subshell. s- and p-
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Chapter_08-Bonds - Chapter 8. Bonds Chapter Chemical bonds...

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