# Biology

Nasra20

Chapter 2 Lecture Participation Assignment

5 points

To complete this assignment, you can either print out this worksheet and fill in your answers or you can fill them in electronically in this word document. When you are done, you will upload your assignment to the ‘chapter 2 participation assignment’ folder found in D2L under assessments à assignments.

1. How many protons in 12C , 13C,  14C, 12C - ?  In  16O , 17O,  18O,?

2. How many electrons in 12C , 13C,  14C, 12C - ?  In  16O , 17O, 18O,?

3. How many neutrons in 12C , 13C,  14C,  12C -?  In  16O , 17O, 18O,?

4. What do all forms of the element carbon have in common (besides the C)?  All forms of O?

5. How are the isotopes of carbon (12C , 13C,  14C) different from each other? The isotopes of O( 16O , 17O,  18O)?

6. What determines the mass number (12, 13,14 or 16, 17, 18 ) in the different isotopes?

Part II: Atomic Structure and Bonding

Atoms do not exist all alone.  Much of the time, atoms bond to other atoms to form molecules.  These molecules can be very large (consisting  of hundreds or thousands of atoms).  For example, the major biological macromolecules (carbohydrates, lipids, proteins, and nucleic acids) are large molecules made up of many C, H, O, and N or P atoms bonded together.

How can we predict if an atom will form bonds with another atom?Examine the model below.

​​​​​​Reactive (form bonds)​​​​​

Not reactive

​​​​​​    (first 7 columns)​     (last column)

Critical Thinking Questions:

7. Based on the model, what is the maximum number of electrons that can be in the first electron shell?8. Based on the model, what is the maximum number that can be found in the 2nd shell?  The 3rd?9. What do you notice about the outer shells of all the nonreactive atoms?10. Can you draw the electron distribution diagram for potassium (K)?

Part III: Types of Bonds

There are 3 major types of bonds:  ionic, covalent, and hydrogen bonds.  There are two types of covalent bonds:  polar covalent and nonpolar covalent.

Model:

Ionic bond:  electrons are transferred from one atom to another in order to fill the atoms’ outer shells.  The resulting ions are attracted to each other due to their opposite charges.

Covalent bond:  electrons are shared by two atoms in order to the fill atoms’ outer shells.

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H2                                                                      O2                                                            H20

1. In the ionic bond model, why does the sodium have a positive charge?  2. In the ionic bond model, why does the chlorine have a negative charge?  3. In the covalent bond model, why don’t any of the atoms have a charge?4. For each of the covalently bonded molecules, circle the shared electrons.5. Look at all of the bonds.  If you count the electrons that are transferred or shared between atoms, do all the atoms have a full outer shell?6. Draw an electron distribution diagram for the formation of methane (CH4).

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