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Prentice Hall Chemistry (c) 2005

Prentice Hall Chemistry (c) 2005. Section Assessment Answers Chapter 6. School is Cool!. 10. On a periodic table of the elements, one might find symbols and names of the elements; atomic number and average atomic mass; information about electron configuration; et cetera.

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Prentice Hall Chemistry (c) 2005

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  1. Prentice Hall Chemistry(c) 2005 Section Assessment Answers Chapter 6 School is Cool!

  2. 10. On a periodic table of the elements, one might find symbols and names of the elements; atomic number and average atomic mass; information about electron configuration; et cetera. • Based on their electron configurations, elements are classified into four categories: • (i) noble gases (full electron shells) • (ii) representative elements (“s-filling” and “p-filling”) • (iii) transition metals (“d-filling”) • (iv) inner transition metals (“f-filling”) 6.2 Section Assessment 12. Sodium and potassium have similar properties because they have similar electron configurations. They both have only one electron in their outermost (“valence”) shell. Consequently, they are placed in the same column in the periodic table (column 1).

  3. a. 1s22s22p63s23p63d104s24p6 = a noble gas (ends in “p6”) 13. b. 1s22s22p63s23p63d64s2 = a transition metal (Notice that the 3d sublevel has only 6 electrons instead of the full 10.) 13. c. 1s22s22p63s23p2= a representative element (The 3p sublevel is the last sublevel listed and it doesn’t have the full 6 electrons that a noble gas would.) 6.2 Section Assessment NOTE: Mr. Barnes is disturbed that in the electron configurations given above, the 3d sublevel is listed before the 4s sublevel. According to Mr. Barnes’ understanding of the aufbau principle, the 4s sublevel is actually at a lower energy level than the 3d sublevel, and, therefore, should be listed first. Either the book or Mr. Barnes is wrong, and neither one of those possibilities is very comforting.

  4. 14. Cu, Cd, Au, and Co are transition metals. They are found in the “d block”, the region that includes columns 3 through 12. 15. According to the teacher’s edition, a group 5A element has five electrons in its highest energy level. Mr. Barnes is troubled by this answer because it seems to be ignoring the possibility of d and f electrons being included in the “highest energy level” for elements found in rows 4, 5, 6, and 7. 6.2 Section Assessment

  5. 16. Generally, atomic size decreases as one goes from left to right across a period (row) in the periodic table. This is in spite of the fact that average atomic mass and atomic number increase. As one goes down a column, atomic size increases, which is more in line with what common sense would predict. 17. Ions form when atoms or molecules lose or gain electrons, thus acquiring a positive or negative electric charge. This can happen when electrons move from one atom to another, but it can also happen when ionizing radiation expels electrons from atoms. It can also occur when extreme voltage is applied across a body of matter, such as when lightning strikes, when a spark jumps across a spark plug gap, or when a fluorescent light bulb is on. 6.3 Section Assessment

  6. 18. As one goes from left to right across a period (row), ionization energy increases. As one goes down a column on the periodic table, ionization energy decreases. The trends for ionization energy are exactly the opposite of the trends for atom size, so it seems that the smallest atoms are the ones that hold on to their electrons the strongest. 19. Cations (positive ions) are smaller than the atoms from which they form. This makes sense, because an atom has to lose electrons to become positive. Anions (negative ions) are larger than the neutral atoms from which they form. This also makes sense, because an atom must gain electrons to become negative. 6.3 Section Assessment

  7. 20. Electronegativity increases as one goes from left to right across a period (row) in the periodic table. Electronegativity decreases as one goes down a column. These are the same trends that ionization energy has. It seems logical that the ability to pull electrons should be closely related to the ability to hold on to electrons. 21. The periodic trends of the elements are explained by looking at the atomic structure of the atoms of those elements. Number of protons, number of electrons, and arrangement of electrons all play a part. Charge and relative location of protons and electrons are factors in determining an element’s properties. 6.3 Section Assessment 22. The following elements are in order of decreasing atomic size: sodium, aluminum, sulfur, chlorine. The arrangement demonstrates a periodic trend, since these four elements are all in period 3 (row 3) of the periodic table.

  8. 23. a. Sodium has a larger first ionization energy than potassium, which is not surprising, since sodium is above potassium on the periodic table. 23. b. Phosphorus has a higher first ionization energy than magnesium, which is not surprising, because phosphorus is to the right of magnesium on the periodic table. 6.3 Section Assessment

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