3:00 2:59 2:58 2:57 2:56 2:55 2:54 2:53 2:52 2:51 2:50 2:49 2:48 2:47 2:46 2:45 2:44 2:43 2:42 2:41 2:40 2:39 2:38 2:37 2:36 2:35 2:34 2:33 2:32 2:31 2:30 2:29 2:28 2:27 2:26 2:25 2:24 2:23 2:22 2:21 2:20 2:19 2:18 2:17 2:16 2:15 2:14 2:13 2:12 2:11 2:10 2:09 2:08 2:07 2:06 2:05 2:04 2:03 2:02 2:01 2:00 1:59 1:58 1:57 1:56 1:55 1:54 1:53 1:52 1:51 1:50 1:49 1:48 1:47 1:46 1:45 1:44 1:43 1:42 1:41 1:40 1:39 1:38 1:37 1:36 1:35 1:34 1:33 1:32 1:31 1:30 1:29 1:28 1:27 1:26 1:25 1:24 1:23 1:22 1:21 1:20 1:19 1:18 1:17 1:16 1:15 1:14 1:13 1:12 1:11 1:10 1:09 1:08 1:07 1:06 1:05 1:04 1:03 1:02 1:01 1:00 0:59 0:58 0:57 0:56 0:55 0:54 0:53 0:52 0:51 0:50 0:49 0:48 0:47 0:46 0:45 0:44 0:43 0:42 0:41 0:40 0:39 0:38 0:37 0:36 0:35 0:34 0:33 0:32 0:31 0:30 0:29 0:28 0:27 0:26 0:25 0:24 0:23 0:22 0:21 0:20 0:19 0:18 0:17 0:16 0:15 0:14 0:13 0:12 0:11 0:10 0:09 0:08 0:07 0:06 0:05 0:04 0:03 0:02 0:01 0:00 Do Now Pick up your exam For the next 3 minutes Examine the questions you answered incorrectly. Compare them with your neighbor and learn from your mistakes. You do not want to make the same mistakes on the second quarter exam. I will answer questions that your neighbor is unable to explain.

A chemical bond is the force of attraction between the atoms of a compound. … but what causes the attraction? Consider the charges of the subatomic particles: o Electrons? o Protons? o Neutrons? So, which part of one atom is attracted to which part of another atom? WRITEDOWN

The electrons of one atom are attracted to the protons of another. When atoms combine, there is a tug of war over the valence electrons. o Valence electrons = outer electrons WRITEDOWN WRITEDOWN

The outcome of a tug of war depends upon the contestants: o If one team pulls hard and the other does not, the team that pulls hard wins. o If both teams pull equally, you have a stalemate where both teams end up holding on to the same rope. The result is similar with a tug of war over electrons: o If one atom has a strong pull on electrons and the other has a weak pull on electrons, the atom with the strong pull gains electrons, and the one with the weak pull loses. o If two atoms pull hard on the same electrons, and neither lets go, they end up sharing those electrons. WRITEDOWN

Imagine a tug of war between sodium and chlorine. Note their locations on the Periodic Table. o How is sodium classified? o How is chlorine classified? o What would happen during a tug of war over valence electrons between sodium and chlorine? WRITEDOWN WRITEDOWN

Draw Bohr-Rutherford diagrams of sodium and chlorine. Fill in the table below: ElementSodiumChlorine Nuclear Charge Charge on Electrons Total Charge

Now draw Bohr-Rutherford diagrams of sodium and chlorine after the electron transfer. Fill in the table below: ElementSodiumChlorine Nuclear Charge Charge on Electrons Total Charge

ions. they are oppositely charged. WRITEDOWN

The electron configurations of sodium and chlorine change when they combine: o Na: Cl: → Na + : Cl – : The charges of sodium and chlorine change when they combine: o Na 0 + Cl 0 → Na +1 + Cl –1  The charge on the ion is the same as its oxidation state or valence.  The sodium and chlorine are attracted because they are oppositely charged.  The charge on the compound is zero.

The electrons of one atom are attracted to the protons of another. Metals hold onto electrons loosely while nonmetals hold onto electrons tightly. Metals lose electrons and nonmetals gain electrons in such a way that they complete their outer shells. o Atoms that gain or lose electrons become electrically charged. o Charged atoms are called ions. o Metals become positively charged ions called cations by losing electrons. o Nonmetals become negatively charged ions called anions by gaining electrons. Metal cations and nonmetal anions become bonded because they are oppositely charged. WRITEDOWN

Bell Work In your own words: – Describe in general how an ionic bond if formed – Give one example of two elements that would form an ionic bond. (do not use NaCl)

Imagine a tug of war between two hydrogen atoms to form a diatomic molecule of hydrogen (H 2 ) o How does the pull of one hydrogen atom on electrons compare to the pull of another hydrogen atom on electrons? o What would happen during a tug of war over valence electrons between two hydrogen atoms?

Sharing valence electrons is called covalent bonding. When it comes to covalent bonding, “sharing is pairing.” o Unpaired electrons pair in such a way that each atom completes its outer shell. Draw electron dot diagrams for each of the hydrogen atoms in the hydrogen molecule. o How many electrons does each hydrogen need to complete its outer shell? The hydrogens are bonded because they are holding on to the same electrons. WRITEDOWN

It is obvious that sodium and chlorine bond ionically, because sodium is a very active metal, and chlorine is a very active nonmetal. It is obvious that diatomic molecules such as H 2 contain covalent bonds because the two identical atoms have the same pull on electrons. But what type of bond is found between hydrogen and oxygen in water? o Oxygen is a nonmetal. o Hydrogen, being at the top of the family, is a metalloid. o They are not as different as sodium and chlorine, nor are they as similar as two hydrogens. Some measure is needed to show how different atoms’ pulls on electrons are. It is electronegativity.

The most metallic element is... o Its electronegativity is... The most nonmetallic element is... o Its electronegativity is... The electronegativity difference is... T HIS IS THE LARGEST ELECTRONEGATIVITY DIFFERENCE POSSIBLE. francium. 0.7, the lowest. flourine. 4.0, the highest. 3.3

The largest electronegativity difference possible is that between francium and fluorine. It is 3.3 o This represents the greatest ionic character. The smallest electronegativity possible is that found within diatomic molecules or between other very similar atoms. It is 0 o This represents the least ionic character. The midpoint is about … o This represents 50 percent ionic character. o It is the dividing line between ionic and covalent. o An electronegativity difference of 1.7 or more represents an ionic bond. Less than 1.7 is covalent. 1.7 WRITEDOWN

Fill in the table below to determine the bond type in water: The electronegativity difference is less than 1.7 The bonds between hydrogen and oxygen are covalent. ElementElectronegativity Oxygen Hydrogen Electronegativity Difference

Not all covalent bonds are created equal. o In the bond between chlorine atoms in a chlorine molecule (Cl 2 ), the electronegativity difference is 0.0, and the atoms share equally. o In a hydrogen chloride (HCl) molecule, the electronegativity difference is not 0.0, and the atoms don’t share equally. Fill in the table below: The bond is covalent, but the atoms don’t share equally. Chlorine is more electronegative. It has a stronger pull on electrons. o The shared electrons will be displaced closer to the chlorine. o This will make the charge on the chlorine side of the bond slightly negative, and on the hydrogen side of the bond slightly positive. ElementElectronegativity Chlorine Hydrogen Electronegativity Difference

In hydrogen chloride the hydrogen side of the bond is slightly positive, and the chloride side of the bond is slightly negative. The earth has opposite ends just like the hydrogen chloride molecule. The opposite ends of the earth are called... The adjective used to describe the bears living at the poles is... Bonds with oppositely charged ends are called polar bonds.NS poles. polar. WRITEDOWN WRITEDOWN

There are three types of chemical bonds: o ionic, o polar covalent, and o nonpolar covalent Bond type is determined by electronegativity difference CovalentIonic NonpolarPolar WRITEDOWN