Bond Type Comparison

1. Bond Type Comparison metallic ionic covalent Init 10/10/2011 by Daniel R. Barnes WARNING: As always, some of the content in this power point, including but not limited to visual images, may have been stolen from the world wide web without the permission of the owners of that intellectual property. Please do not copy or distribute this presentation. Its very existence may be illegal.

2. S.W.B.A.T. . . . compare and contrast ionic bonding, metallic bonding, and covalent bonding.

3. Ionic Bonds * when a metal bonds with a nonmetal * Nonmetal takes electrons from the metal. * non-conducting when solid, but conductive when molten from high temp. OR when dissolved in water * forms ionic crystals * Positive cations are attracted to negative anions. * No sharing of electrons. Electrons are given and taken, not shared. Nonmetals cling hard to the electrons they take. * Material tends to be hard, brittle solid with a high melting and boiling point. Crystals may glitter, but material is not lustrous.

4. Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ IONIC CRYSTAL

5. Ionic crystals tend to be brittle. If you smack them with a hammer, they tend to shatter Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ In this salt crystal, +’s are next to –’s, so everybody is attracted to their nearest neighbors, causing the crystal to stay together. If you smack it with a hammer . . . The part of the crystal you hit will dislocate and slide until + is next to + and – is next to - This will cause the part that moved to be repelled by the part that didn’t move, breaking the crystal in two.

6. What do neighboring cations and anions feel for each other? Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ attraction What do two +’s next to each other or two –’s next to each other feel? repulsion

7. Metallic Bonds * when a metal bonds with itself (pure metal) or another metal (alloy) * Metal atoms give off electrons to become positive cations. * Good conductors of heat and electricity, even when solid * Forms metallic crystals, though these may be too small to see

8. Bismuth crystals

9. Brass microstructure

10. Sometimes, metal crystals are big enough to see. This is a mass of platinum crystals.

11. Metallic Bonds * when a metal bonds with itself (pure metal) or another metal (alloy) * Metal atoms give off electrons to become positive cations. * Good conductors of heat and electricity, even when solid * Forms metallic crystals, though these may be too small to see * Materials tend to be malleable solids with high melting and boiling points (although 1A are soft and Hg is liquid!). * Positive cations are attracted to negative “sea” of freely-flowing electrons in between the cations. * Electrons given off by metal atoms are shared equally by all positive cations in the chunk of metal in question. They belong to everyone, yet to no one in particular. Electrons wander freely.

12. Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ METALLIC BONDING

13. Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ NOTE: I’m not 100% sure if Al cations in a chunk of pure alumnimum really have a charge of 3+. I’m just guessing that based on their location on the PT.

14. Covalent Bonds * Happens when a nonmetal atom bonds with another nonmetal atom. Atoms can be same or different element. * forms molecules (water, carbon dioxide, oil, plastic) or network solids (diamond, graphite). * pairs of electrons shared between two atoms * Positive nuclei are attracted to negative electrons shared between them. * Electrons are shared exclusively and privately by the atoms that share them. No one else is involved. Electrons not free to wander. * poor electrical conductors = “insulators” * Material may be brittle, smushy, liquid, gaseous, elastic, or any number of possibilities.

15. Hydrogen gas is made of molecules, each of which is made of two atoms that are covalently-bonded to each other. H H H H The two atoms in an H2 molecule share a pair of electrons. H H The two atoms in this molecule share these two electrons with each other and only with each other. Even if others molecules come very close, the atoms in this molecule share electrons only with each other, not with atoms from other molecules.

16. Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ IONIC The ratio of sodium to chloride is the same (1:1), so it’s still the same chemical with the same properties. table salt still table salt still table salt A salt crystal can have twelve million sodium atoms, as long as it has twelve million chlorine atoms. Yep. It’s still table salt. Na8Cl8 = NaCl. Same stuff.

17. H H H H H H Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- O O O Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ IONIC COVALENT table salt H2O This is a water molecule. H4O2 NaCl This is NOT a water molecule. In fact, this is an unstable monster that would not exist for long.

18. Bond Type Comparison Summary Chart Bond Type Basis of bond Role of electrons Electrical Conductivity Elements bonded + nuclei like - shared electrons varies but generally poor shared exclusively Covalent NM & NM + cations like - anions only when melted or dissolved given & taken Ionic Met & NM + cations like - wandering electrons shared communally very conductive Metallic Met & Met

19. Did you get it? Q1: In what kind of bonds are electrons shared? A: covalent and metallic Q2: What kind of bond typically forms between a metal and a nonmetal? A: an ionic bond Q3: What is bonding, anyway? A: when atoms stick to each other really hard Q4: Why are metals good conductors? A: The shared electrons are free to wander from atom to atom. They form a “sea” of electrons that can flow. Q5: What is a covalent bond made of? A: one or more shared pairs of electrons

20. Did you get it? Q6: How can you make a salt crystal conduct electricity? A: melt it with extreme heat or dissolve it with water Q7: Salt is made of positive and negative ions. What is made only of positive ions? A: metals Q8: What do you call a mixture of two or more different metals? A: an “alloy” Q9: Give an example of an alloy and what it’s made of. A: Many examples are possible, including bronze, which is made of copper & tin, or brass (Cu & Zn). Q10: What do you call a small cluster of nonmetal atoms covalently bonded together? A: a “molecule”