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Chemical Bonding. What is a Bond?. Tell me what you know. Are there stronger bonds? Weaker bonds? What happens to make a bond? Would a song help? The Chemical Bonds Song (to the tune of Dancing Queen) Now tell me the differences!. Bond… but not James Bond.

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Chemical Bonding

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Presentation Transcript
what is a bond
What is a Bond?
  • Tell me what you know.
    • Are there stronger bonds? Weaker bonds?
    • What happens to make a bond?
    • Would a song help?
    • The Chemical Bonds Song (to the tune of Dancing Queen)
    • Now tell me the differences!
bond but not james bond
Bond… but not James Bond
  • Sadly, chemical bonds are *not* hunky secret agents played by Pierce Brosnan and Sean Connery.
  • However! Without chemical bonds, we wouldn’t have James Bond, actors, movies, or life at all! So, even though chemical bonds don’t shoot bad guys, drive awesome cars, or save the day, they’re still pretty darn important!
bond types
Bond Types
  • But if we had to compare to secret agents, let’s look at it this way.
    • Ionic Bonds are when one atom transfers an electron to another – sounds pretty sneaky if you ask me. So here, you’re looking at an agent pulling off a mission and ‘delivering the package’.

Even secret agents can’t do it all alone – they have to answer to someone… unless they go rogue. But in chemistry, Bonds don’t go rogue.

more bond types
More Bond Types
  • Does anyone remember in Goldeneye when 007 was working with 006 on a mission at the beginning? Well, covalent bonding is what’s going on here. Sometimes, neither atom has what it takes to complete thejob alone. So, they pool theirskills and resources (inchemistry, they share theirelectrons) so that the jobstill gets done.
there is one more type
There is one more type
  • In the world of James Bond, there isn’t just one or two secret agents. There are hundreds, all doing missions just as dangerous as James does (but James is the only one who gets movies made about him ). Bond works for an organization that does missions all over the world – its called MI6.
metallic bonding
Metallic Bonding
  • MI6 is a lot like a thing called metallic bonding. When you have a metallic bond, its not quite an electron transfer, but its more than just sharing among two agents. ALL ofthe agents share theirresources so that all the jobsget done.
  • Electrons in this bond typeare free to go wherever theyare needed – they aren’t‘kept’ by any one atom.
comparing the bonds
Comparing the bonds
  • It all has to do with filling the valence shell of electrons.
ionic bonding
  • Ionic bonds form when there is an electron transfer
  • Once the transfer is complete, each atom becomes an ion with a + or – charge.
  • The ionic bond, then, is the force of attraction due to opposite charges – this is called electrostatic force
  • A positively charged ion is called a cation. A negatively charged ion is called an anion. (The cation loses electrons, the anion gains electrons.)
the octet rule
  • So why do things bond in the first place? They want a full valence shell – that’s the outer shell of electrons.
  • Hydrogen and helium have a valence shell that holds only 2 electrons. All other elements have a valence shell that holds 8 electrons. When atoms bond, they gain or lose electrons so that they can have a full outer shell - this is called the octet rule(this is because most elements have an outer shell of 8 electrons.)
  • It is important to know that the octet rule doesn’t ALWAYS apply. It is a useful guide, but there are exceptions.
the octet rule1
  • Looking at the periodic table can give you hints about how atoms will bond.
  • Elements in the first column (H, Li, Na, K…) have 1 electron in their outer shell, so its easier for them to lose that electron to get a full outer shell (their next one in). This means they have a +1 charge when they bond. This also works for the second column (+2 charge, lose 2 electrons)
  • After that, you have to skip to the 13th (B, Al, Ga, etc.) where the pattern continues.
metal and nonmetal
Metal and Nonmetal
  • Based on that, you can see that most of the metals in our counting method have a charge of +1 to +4. On the other side, nonmetals (like oxygen, nitrogen, carbon, etc.) usually have a charge of -1 to -4.
  • For most metals, its easier to lose a couple electrons than to gain 5 or 6. For nonmetals, its easier to gain a couple. This is why metals and nonmetals easily bond.
lewis dot structure
Lewis Dot Structure
  • A man named Gilbert Newton Lewis invented a way to represent valence electrons. (1902)
  • It uses Lewis Dot Symbols

The ions ---------------> The ionic bond

lewis dot diagrams
Lewis Dot Diagrams
  • When drawing a Lewis dot diagram, there are rules.
    • Start with the element symbol in the center.
    • Find the number of valence electrons
    • Each dot means one electron, and dots can be placed above, below, and on both sides of the element
    • Each side can hold 2 electrons
    • You can’t put 2 dots on any side until each side has at least 1
predicting formulas
Predicting Formulas
  • Using Lewis dot diagrams, you can predict formulas of compounds
  • Sodium (Na) has 1 valence electron, while chlorine (Cl) has 7 valence electrons.
  • So, transferring an electron from sodium to chlorine makes both of them ‘happy’ - so its just NaCl
ionic crystal structure
Ionic Crystal Structure
  • Ionic substances don’t just bond to make single molecules. The electrostatic attraction makes them bond into large structures, getting as many as possible as close as possible. These are called crystallattices.