Chem 115 Activity 6

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Dec 6, 2023

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Chem 115 Activity 6 Introduction: This activity covers sections 2.7-3.4 from the text including objectives 2.7-3.4. This is an in-class activity! You will find on BlackBoard an assignment that will ask you to enter some of your answers. Some of these questions will be duplicated there. You will get five attempts at each question, so this will allow you to check your answers, as well as receive a grade. If you are unsure of your answer after four attempts, you should ask for help. Not all questions will be graded, but you will still be asked to enter a response. When discussing answers with your group, make sure you not only agree on answers, but also why they are correct. Can you verbally defend why your answer is correct? Valance Electrons Learning Objective 2.8: Identify the valence shell electrons for an atom, and which subshell of electrons (s, p, d, f) correlate with which groups in the periodic table. Learning Objective 3.2: Use the octet rule and electron configurations to explain the charge associated with ions. Model 1: Incomplete diagrams of a magnesium (Mg) atom using the shell model (a) and the core charge concept (b) 1. Label the shells in Model 1(a) as 1, 2, 3, etc. 2. Why is the nuclear charge of Mg “+12”? Because it has 12 protons 3. Remembering your results from activity 5, how many electrons completely fill the first shell? _2___ a. How many electrons fill the second shell? _8____ 4. How many inner shell (core) electrons does Mg have? __10___ 5. How many total electrons should Mg have, based upon its atomic number? ___12___ 1

6. If Mg has the number of electrons you indicated in #5, how many valence electrons will Mg have? __2___ Add them onto the shell model (a) in the diagram above. 7. Work with your team to complete diagram (b) of a magnesium (Mg) atom using the core charge concept. 8. What do Mg and all group 2 elements have in common? The same number of valence electrons 9. As a team , predict whether Mg will likely gain or lose electron(s) to achieve a full octet when it forms a compound. How many electron(s) will be gained or lost? Lose electrons it will lose 2 Arrangement of the Periodic Table Learning Objective 2.7: Write the electron configuration for an atom to describe how electrons are distributed into specific orbitals. Learning Objective 2.8: Identify the valence shell electrons for an atom, and which subshell of electrons (s, p, d, f) correlate with which groups in the periodic table. Refer to the Periodic Table. Notice that the Periodic Table is arranged in specific block format with two columns on the left, ten in the middle, and six on the right. 10. Recall you work on Activity 5. What is the electron configuration for Na. 1s^2 2s^2 2P^6 3S^1 11. How many electron shells does potassium (K) have? ___4__ Radium (Ra)? _7____ 12. What correlation exists between the number of electron shells an atom has and the row number in which the element is found in the Periodic Table? The row correlates with the number of shells As you go to the right on the periodic table the elements have more valence electrons 13. How many electrons does Mg have? ___12__ Ar? ___18__ 14. Ar has six more electrons than Mg. What is the major difference in the electron configuration of Mg and Ar? Mg has no 3p/ full 3s, Ar has a full 3p It has a extra shell 15. How many electrons can the 2s subshell hold? __2__ 16. How many electrons can the 2p subshell hold? __6__ 17. The Periodic Table is divided into “blocks.” Consider the second row, which spans two blocks. One block consists of two rows on the left, and the other consists of six rows on the right. What correlation exists between the number of columns in a block and the number of electrons that a particular subshell can hold? The block on the left is 2 rows and it is a S block so it can hold 2 electrons, same with the block on the right that spans 6 columns 2

Ions and the Periodic Table Learning Objective 3.2: Use the octet rule and electron configurations to explain the charge associated with ions. Learning Objective 3.3: Use the periodic table to predict the charge associated with ions of main group elements. Learning Objective 3.4: Explain the formation of anions and cations based on periodic trends. Model 2: Common changes (by group) on elements when in ionic compounds . Keep in mind that the numbering on the columns in this periodic table are different than those used in our videos lectures. Conversion to the A/B system: 1 = 1A, 2 = 2A, 13 = 3A, 14 = 4A, 15 = 5A, 16 = 6A, 17 = 7A, and 18 = 18A. 18. How many valence electrons are found in atoms in a. group 1? 1 b. group 13? 3 c. group 16? 6 19. When atoms form ionic compounds, they often fill out their valence shell ( octet rule ) by either gaining or losing 1, 2 or 3 electrons. Based on your answer to #18, indicate how many electrons these atoms would either gain or lose to achieve an octet. a. group 1? Lose 1 b. group 13? Lose 3 c. group 16? Add 2 3

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20. What would be the resulting charge on the ions created in #19 when electrons are gained or lost? a. group 1? +1 b. group 13? +3 c. group 16? -2 21. Based on your response to #20, do metals typically form anions or cations ? Cations 22. Do nonmetals typically form anions or cations ? Anions Ions in Compounds Learning Objective 3.1: Describe ion formation processes and distinguish between anions and cations. Model 3: Compound Formation 23. How many electrons did lithium donate? _1____ How many did bromine accept? __1___ 24. Based on the electron configuration, which noble gas does lithium (Li + ) now resemble? _He____ 25. Based on the electron configuration, which noble gas does bromide (Br - ) now resemble? _Kr____ 26. Both the lithium ion and the bromide ion have charges. What is the net (total) charge on the compound (LiBr) what is formed in Figure 2? __Neutral___ Ensure that all team members understand how you arrived at this answer. 4

Additional Questions: Work on these questions if you complete everything else during class. Complete these after class if needed for extra practice. 1. Why are there only two elements in the first row of the periodic table? Because they only have one shell 2. For the following atoms, predict the number of electrons that would be gained or lost to form an octet in the outermost shell: K, N, H, Br, Al. 1. -1 2. +3 3. -1 4. +1 5. -3 3. A student makes the following statement: “The electron configuration of all halogens ends in p 5 .” Is the student correct? Explain. True because in group 7 they should end like that 5