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22 Cards in this Set
- Front
- Back
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Why is salt hard?
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The type of bonding within a substance
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What happens when atoms bond ?
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Bonding lowers the potential energy between positive and negative particles
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What is ionic bonding?
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Electron transfer
Happens between metal and nonmetal Large tendencies to lose or gain electrons Metal loses electron, nonmetal gains electron |
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What is covalent bonding?
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Electron sharing
Usually Between nonmetal and nonmetal |
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What is metallic bonding?
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All the metal atoms in a sample pool their valence electrons into an evenly distributed “sea” of electrons that flows between and around the metal-ion cores and attracts them, thereby holding them together.
Delocalized |
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What is the Lewis electron-dot symbol
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Method for showing valence electrons of interacting atoms
Element symbol~nucleus and inner electrons Dots~ valence electrons |
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What is the octet rule?
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When atoms bond, they lose,gain, or share electrons to fill their outer level or 2 or 8 electrons
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What is the ionic bonding model?
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transfer of electrons from metal atoms to nonmetal atoms to form ions that come together in a solid ionic compound
the total number of electrons lost by the metal atoms equals the total number of electrons gained by the nonmetal atoms |
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What are the energy considerations of ionic bonding?
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• The electron-transfer process absorbs energy
• Ionic compounds form due to the release of energy that occurs when ions come together and form the solid • Strong attraction between oppositely charged ions • More energy is released when gaseous ions coalesce into a crystalline solid |
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What is the importance of lattice energy?
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The enthalpy change that accompanies the separation of 1 mol of ionic solid into gaseous ions
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What is the Born-Harper cycle?
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• A series of chosen steps from elements to ionic compounds for which all the enthalpies are know except the lattice energy
• Ionic solids only exist because the lattice energy exceeds the energetically unfavorable electron transfer • The energy required for elements to lose or gain electrons is supplied by the attraction between the ions they form |
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What is Coulomb’s Law?
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• Electrostatic force between two charges is directly proportional to the product of their magnitudes and inversely proportional to the distance between them
• Fig 1 • In connection electrostatic energy = force * distance, therefore fig 2 • Lattice energy = electrostatic energy, fig 3 |
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What is formal charge?
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• a fictitious charge assigned to each atom in a Lewis structure that helps to
distinguish among competing Lewis structures. • The charge if all bonding electrons were shared equally (between bonded atoms) • number of valence electrons(VE) of H – (number of lone pair electrons in H(LP) + 1/2 *number of bonding electrons of H(BE) • formal charge=VE-(LP+1/2BE) • formal charge=Voodoo Eagle-(Lone Paradise + ½ Big Elephant) =”VELPBE” |
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What are the Rules for Formal Charges?
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1. The sum of all formal charges in a neutral
molecule must be zero. 2. The sum of all formal charges in an ion must equal the charge of the ion. 3. Small (or zero) formal charges on individual atoms are better than large ones. 4. When formal charge cannot be avoided, negative formal charge should reside on the • most electronegative atom |
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What happens as you go down a period?
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1. atomic radius increases
2. electronegativity decreases |
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How many electrons are shared in a double bond? a triple bond?
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4 electrons, 6 electrons
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What happens as you go from left to right in a family(death row)?
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1. atomic radius decrease
2. electronegativity increases |
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What is average bond energy aka bond strength ?
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-The energy needed to overcome the strength between the mutual attraction of bonded nuclei and shared electrons
-The energy difference between separated atoms and bonded atoms |
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What happens when bonds are formed? When bonds are broken?
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• When bonds are formed, the enthalpy change is –
• When bonds are broken, the enthalpy change + |
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What happens to bond energy as bond length increases? Decreases?
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• As bond length inc, bond eng dec
• As bond length dec, bond eng inc, shorter is stronger |
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How can you find the heat of reaction?
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Sum of the energy of bonds broken + sum of energy bonds formed (should be a negative number)
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If covalent bonds are so strong, why do so covalent substances have such low melting and boiling temperatures?
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True, covalent bonds are strong, but they are only for holding the atoms together
It is the weak intermolecular bonds holding the molecules near each other, that is responsible for the physical properties of covalent substances |
