An instructor gave you directions to construct a model of the CH3CH2Br molecule by following t Experimental Procedure section of your experiment. First, you will need to find the number of valence electrons in CH3CH2Br. The number of va ence electrons in an atom of an element is said to be equal to the last d git in the group number of that element in the Periodic Table. How many sticks do you need if the electrons in the molecule are paired, and each post constitutes an electron pair? 9. An instructor gave you directions to construct a model of the CH3CH2Br molecule by following the Experimental Procedure section of your experiment. Now you assemble a skeleton structure for the molecule by connecting the balls with sticks into one unit. A ball has holes representing how many bonds an atom can form. You use the rule that C atoms form four bonds, while Br atoms usually do not. What is the sketch of the skeleton? 10. An instructor gave you directions to construct a model of the CH3CH2Br molecule by following the Experimental Procedure section of your experiment. How many sticks did you use to make the skeleton structure? 11. An instructor gave you directions to construct a model of the CH3CH2Br molecule by following the Experimental Procedure section of your experiment. How many sticks are left over after making the skeleton structure? 12. An instructor gave you directions to construct a model of the CH3CH2Br molecule by following the Experimental Procedure section of your experiment. What is the Lewis structure for CH3CH2Br?
8.  An instructor gave you directions to construct a model of the CH3CH2Br molecule by following t Experimental Procedure section of your experiment. First, you will need to find the number of valence electrons in  CH3CH2Br. The number of va ence electrons in an atom of an element is said to be equal to the last d git in the group number of that element in the Periodic Table. ÂÂ
How many sticks do you need if the electrons in the molecule are paired, and each post constitutes an electron pair?
The Correct Answer and Explanation is :
To construct a model of the CH3CH2Br molecule, let’s first determine the number of valence electrons in the molecule, as these will guide the bonding structure and thus the number of sticks needed in the model.
Determining the Valence Electrons:
- Carbon (C) – Each carbon atom belongs to Group 14 of the Periodic Table, which means it has 4 valence electrons. The molecule has two carbon atoms.
- Hydrogen (H) – Each hydrogen atom belongs to Group 1, having 1 valence electron. There are five hydrogen atoms in CH3CH2Br.
- Bromine (Br) – Bromine belongs to Group 17, meaning it has 7 valence electrons.
Total valence electrons calculation: Total Valence Electrons=(2×4)+(5×1)+7=8+5+7=20\text{Total Valence Electrons} = (2 \times 4) + (5 \times 1) + 7 = 8 + 5 + 7 = 20
Constructing the Skeleton Structure:
- The CH3CH2Br molecule consists of a chain of two carbon atoms, with the first carbon (in CH3) bonded to three hydrogen atoms and the second carbon (in CH2). The second carbon is bonded to two hydrogen atoms and a bromine atom. The carbons are connected by a single bond.
Sticks Required for Bonding:
- Each stick represents a pair of electrons. Bonds in organic molecules are typically single (two electrons), double (four electrons), or triple (six electrons) bonds.
- For CH3CH2Br, all bonds are single bonds:
- C-C bond: 1 stick
- Three C-H bonds in CH3: 3 sticks
- Two C-H bonds in CH2: 2 sticks
- One C-Br bond in CH2Br: 1 stick
Total sticks used: 1+3+2+1=71 + 3 + 2 + 1 = 7 sticks.
Lewis Structure of CH3CH2Br:
To draw the Lewis structure:
- Place the two carbon atoms in the center with a single bond connecting them.
- Attach three hydrogen atoms to the first carbon and two hydrogen atoms to the second carbon.
- Attach the bromine atom to the second carbon.
- Ensure each hydrogen is connected by a single bond (one pair of electrons), each carbon is forming four bonds, and bromine forms a single bond with the second carbon.
Sticks Left Over:
If we consider that each stick represents a bonding pair and you started with sticks equal to the total valence electrons (20 electrons or 10 pairs):
- You used 7 sticks for the bonds.
- Sticks left over: 10−7=310 – 7 = 3 pairs of electrons, which are unaccounted for in the skeletal structure as these are not needed for additional bonding in the simple Lewis structure representation.
In summary, constructing a model of CH3CH2Br in a classroom setting using balls (for atoms) and sticks (for bonds) provides an interactive way to visualize molecular structure, emphasizing the connections between atom types and their valence electron counts to form a stable compound.