I. Multiple Choice: Select the best/correct answer.
1. Who proposed the probability that electrons will be found in certain locations around the nucleus of an atom?
A. Neils Bohr C. Ernest Rutherford B. Erwin Schrodinger D. J.J. Thomson
2. Which of the following statements is NOT true of the atomic model of Bohr?
A. The hydrogen is made up of a positively charged nucleus B. The electron revolves around the nucleus in a circular orbit.
C. The energy of the electron in a given orbit is not fixed. D. An electron can absorb or emit a quantity of radiation.
3. Which orbital designation has the highest energy?
A. 2s B. 2p C. 3d D. 4s 4. Which statement is incorrect?
A. Orbital is a region in an atom where an electron can be found.
B. An electron can absorb energy when it jumps to a higher energy level.
C. An electron can emit energy when it jumps to a higher energy level.
D. Filling of electrons in an atom start from lower energy level to highest energy level.
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18 5. What occur when an electron moves from high energy level to a low one? A. another electron goes from a low energy level to a high one
B. the atom moves faster
C. colored light is given off D. this process is not possible
6. Which combination describes the flame color of the compound when heated? A. sodium chloride – orange C. potassium chloride – blue
B. copper(II) sulfate – violet D. boric acid – red
II. Shown here are orbital configurations for the elements named. Each configuration is incorrect in some way. Identify the error in each and write the correct configuration. 1. carbon : 1s2 2s2 2px2 2. calcium: 1s22s22px22py22pz23s23px23py23pz23d113d21 3. chlorine: 1s22s22px22py22pz23s23px23py24s1 4. aluminum: 1s22s22px22py22pz23s23d11 5. titanium: 1s22s22px22py22pz23s23px23py23pz2 3d12 3d22 References:
Brown, Theodore, LeMay, H.Eugene,Bursten, Bruce, Murphy, Catherine, Woodward, Patrick (2009) Chemistry: The Central Science 11th Edition Pearson Education,
South Asia PTE. LTD. Singapore
Carmichaels, H. (1983). Laboratory chemistry,. Columbus, Ohio: Merrill Publishing Co. Department of Education, Culture and Sports. (2004).Chemistry:Science and
Technology textbook for 3rd year. (Revised Ed.). Quezon City: Author.
Kotz, John C. , Treichel, Paul M. Townsend, John R. (2010) Chemistry and Chemical Reactivity Enhanced Ed. Canada: Brooks/Cole Cengage Learning.
LeMay, E, Beall, H., Roblee, K. & Browser, D..(1996). Chemistry Connection to Our Changing world, Teacher Edition.New Jersey: Prentice Hall, Inc.
Mendoza, E. & Religioso,T. (2001). Chemistry. . Quezon City:Phoenix-SIBS Publishing House,Inc..
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19 Silberberg, Martin S., (2009) Chemistry: The Molecular Nature of Matter and Change 5th
Edition, International Edition 2010 McGraw-Hill, McGraw-Hill Companies, Inc., New York
Smoot, R.C. Smith, R.G & Price, J.(1995) Chemistry Wraparound Teachers Edition, Glencoe/McGraw-Hill, Merril Publishing Co., Ohio
The ekShiksha Team, Affordable Solutions Lab(ASL), Indian Institute of Technology, Bombay, India (n.d). Matter in our surroundings. Retrieved: October 3, 2013. http://www.it.iitb.ac.in/ekshiksha/eContent-Show.do?document!d=88
University of the Philippines National Institute for Science and Mathematics Education Development. (2001). Practical work in high school chemistry: Sourcebook for teachers. Quezon City: Author.
Wilbraham, A.C., Staley, D.D., & Matta, M.S.(1997). Chemistry expanded.(4th
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20
Chemical Bonding
Overview
It is interesting to look back at the lessons you have learned about matter when you were in grades 7 and 8. Do you still remember them? Yes! In grade 7, you were able to describe the properties of metals and non-metals and to recognize elements and compounds. In Grade 8, you observed different common changes such as evaporation, condensation, boiling, and melting that helped you learn about the particles that matter is made of. You have also learned that the elements are systematically arranged and grouped in the Periodic Table of Elements. Your knowledge about matter is continuously growing. In fact, in the previous unit you were introduced to how electrons in different atoms are distributed. You have learned a lot so far!
Studying this module will certainly increase your understanding about matter. Get your periodic table. What do you notice about the electronic configuration of the noble gases? You’re right! Except for helium, all of them have eight electrons at the outermost energy level. The sharing or the complete transfer of electrons causes an atom to have the same electronic configuration as that of the nearest noble or inert gas. The sharing or the complete transfer indicates that the atom has attained stability. Either the sharing or the complete transfer of electrons leads to the formation of compounds.
Going through this module will make you understand what is happening in the atoms during the formation of compounds. Look at the periodic table. Did you notice the vertical arrangement of the elements? This is called family or group. Notice the number in each group? Do you know what information it gives you? It tells about the number of valence electrons. Do you still remember the meaning of valence electrons? Valence electrons give you the number of electrons at the outermost energy level of the atom. This is the information you need to know in order for you to determine whether atoms transfer, accept or share electrons to become stable. Why do we need to talk about the transfer or the sharing of electrons? You will discover the answer to this question as you study this module.
Further, you will find out the answer to the following questions.
Suggested Time allotment: 14-16 hours
Unit 2 MODULE
2
How are ionic and covalent compounds formed?
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21 The following objectives will help you focus as you about studying this module.
Learning Competencies/Objectives
Explain the formation of ionic and covalent bonds.
Recognize different types of compounds (ionic or covalent) based on their properties such as melting point, hardness, polarity and electrical and thermal conductivity.
Explain properties of metals in terms of their structure. Explain how ions are formed.
Before you study this module, please answer the pre-assessment below. Pre-Assessment:
Direction: Encircle the letter of the best answer for each question.
1. Which of the properties of atoms is the most suitable reference for the kind of bond that will take place between/among them?
a. atomic size b. electronegativity c. ionization energy d. electron affinity 2. What kind of particle is produced after covalent bonding?
a. atom b. molecule
c. ion d. electron 3. How does ionic bonding take place?
a. Two non-metallic elements of different kinds form strong forces of attraction. b. Two non-metallic element of the same kind form strong forces of attraction. c. A non-metallic element like fluorine is attracted to a metallic element like sodium. d. A metallic element like sodium transfers an electron to a non-metallic element like fluorine.
4. What kind of chemical bond will form between two oxygen atoms?
a. ionic bond b. metallic bond
c. polar covalent bond d. nonpolar covalent bond
5. Which of the following type of bonds will have the highest electrical and thermal conductivity?
a. ionic bond b. metallic bond
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22 6. Why can metals be hammered without breaking?
a. They are ductile. b. They are not brittle. c. They are malleable. d. Its particles are strong.
7. When does covalent bonding take place?
a. It takes place when atoms share electrons with one another. b. It takes place when the attraction between atoms is strong. c. It takes place when atoms collide with one another.
d. It takes place when atoms attain stability.
8. Nitrogen (N) belongs to family 5A and it is diatomic. How many nonpolar covalent bonds will there be in N2 molecule?
a. 1 b. 2 c. 3 d. 4
9. Which of the following will have the highest melting temperature?
a. sodium chloride (salt) b. paraffin wax (candle wax) c. sucrose (table sugar) d. lead wire
10. Which among the following shows that an atom is stable?
a. having 2 valence electrons b. having 4 valence electrons c. having 6 valence electrons d. having 8 valence electrons After doing this pre-assessment, you are now ready to do the succeeding activities of this module.
There are concepts you need to know in order to fully understand why atoms form compounds. Let us start with the basic information, the number of valence electrons, octet rule and electronegativity.