If you have questions or comments about chapter 3, please post them here. If you know the answer to a posted question, please edit the page and post your answer.
Corrections to Solution Manual
14b. The correct answer is C > B > A.
16c. It doesn't list K, which is diamagnetic.
18b. The number of core electrons and valance electrons for Xe are listed as 54 core and 0 valance, but a more accurate description would be 46 core and 8 valance.
-Mel
Electronegativity of Noble Gases
Noble gases (He, Ne, Ar, Kr, etc.) do not have electronegativity. The textbook defines electronegativity as a measure of the ability of an atom to attract bonding electrons to itself. Remember, noble gases have their valence shells filled with electrons, so they have no desire to attract any more electrons. Only atoms with unfilled orbitals have electronegativity. -Mel
Orbitals at higher energy & Electronegativity
-I don't get 4 b&c., because in the solutions manual it says Se has 51 protons, is it a mistake or am I just not getting it.
4b. Yes, Se has 34 protons, not 51. Since Se has more protons (with 34) attracting the electrons in its 3s orbital than S with only 16 protons, the 3s orbital in S has higher energy. -Mel
4c. The same reasoning goes for C and O. Since O has 8 protons and C has 6 protons, O has a stronger attraction of the electrons in the 2p orbital toward to nucleus than does C. Therfore, the 2p orbital of C has higher energy. -Mel
-Also can someone explain #13 a and c, and why the atoms are more electronegative.
13a. Electronegativity increases moving up and to the right in the periodic table. Looking at N, O, and P in the periodic table, which one is closest to the top and closest to the right? N and O are further up than P, so P is not the correct answer. Now it's between N and O. O is more to the right than N, so N is not the correct answer. The correct answer is O, which is most electronegative. -Mel
13c. Electronegativity increases moving up and to the right in the periodic table. Looking at Si, P, and S in the periodic table, which one is closest to the top and closest to the right? All three are in the same period, so none are further up than the others. It's still between Si, P, and S. S is more to the right than P and Si, so P and Si are not the correct answer. The correct answer is S, which is most electronegative. -Mel
Can someone explain number 4?
#4.When you are given two orbitals and you are asked to determine which orbital is at a higher energy, answer the following questions:
1. Which has the highest quantum number n? Generally, the higher the 'n' value, the higher the orbital energy. If the two orbitals you are asked to compare have the same value for n, move on to the next question.
2. Which atom has the least number of protons? The lower the protons, the higher the energy.
Also, please read the info already on this page that explains #4b and #4c.
Caveat: Comparing n values can get tricky when d orbitals are involved. The actual way to compare two orbitals as in question 1 above is to calculate n+L for each orbital, and the highest value has the highest energy. For example, if you are asked to compare a 4s orbital and a 3d orbital of an atom, 3d has the higher energy. This is because n+L for 4s is 4+0=4, and n+L for 3d is 3+2=5. Since this type of calculation was not required for the assigned chapter problems, I would not expect to see it on an exam, but just be aware that comparing only the n values does not work in every situation. -Mel
IE, Electronegativity, atomic radius
I am very confused!!!!! How would I find the greatest and smallest of each of these???
These all follow trends based on the periodic table, which are illustrated in Figure 3.8 on page 66 of your textbook. Just memorize the trend of atomic radii, and then remember that the trends of ionization energy and electronegativity are in the opposite direction as atomic radii. Then you use the periodic table to determine relative IE, electronegativity, and atomic radii (atomic size) of different atoms.
Also, please read the info already on this page that explains #13a and #13c. -Mel
For number 12 how do you know the biggest atom?? also number 18 .<3 Heidi
#12.First, look at Figure 3.8 on page 66 of your textbook. It shows that atomic radii (another way to say atomic size) gets bigger as atoms move left and down the periodic table. Then compare the atoms that are given to find the biggest atom.
Looking at the periodic table, you can ask two questions to find the biggest atom. (1) Which atom is furthest to the left? (2) Which atom is furthest down? Looking at these 4 atoms, C is the furthest to the left, and P is the furthest down, so now you narrowed it down to only two atoms. It just so happens that atomic radii make little changes going left-to-right and bigger changes going top-to-bottom within the periodic table. So, look at C and P in relation to N. If the atomic size makes a little change going left to C but makes a bigger change going down to P, which one is bigger? The answer is P.
Again, looking at the periodic table, you can ask two questions to find the biggest atom. (1) Which atom is furthest to the left? (2) Which atom is furthest down? Looking at these 3 atoms, N is furthest to the left, and they are in the same period (none are further down than the others), so which one is biggest? The answer is N.
Again, looking at the periodic table, you can ask two questions to find the biggest atom. (1) Which atom is furthest to the left? (2) Which atom is furthest down? Looking at these 3 atoms, they are in the same group/family (none are further left than the others), and Br is the furthest down, so which one is the biggest? The answer is Br.
You may need to memorize the trend for atomic radii, and then just remember that the trends for ionization energy and electronegativity are opposite of atomic radii.
-Mel
18.The question is asking you to determine the number of core electrons and valence electrons for certain atoms. The definition of core electrons is the number of electrons that are not considered valence electrons. Remember that a quick method to determine the number of valence electrons of an atom is to look at the periodic table to see what group it is in.
[CORE ELECTRONS = TOTAL ELECTRONS - VALENCE ELECTRONS]
a) Na is in the 1A group, so it has 1 valence electron. Since Na has 11 total electrons, the number of core electrons is 11-1=10.
b) Xe is in the 8A group, so it has 8 valence electrons. Since Xe has 54 total electrons, the number of core electrons is 54-8=46.
c) S is in the 6A group, so it has 6 valence electrons. Since S has 16 total electrons, the number of core electrons is 16-6=10.
d) Ga is in the 3A group, so it has 3 valence electrons. Since Ga has 31 total electrons, the number of core electrons is 31-3=28.
-Mel
Q: Okay, this is just a clarification on electron configurations, starting with the 1S level and going up:
1S - 1 space - 2 electrons
2S - 1 space - 2 electrons
2P - 3 spaces - 6 electrons
3S - 1 space - 2 electrons
3P - 3 spaces - 6 electrons
4S - 1 space - 2 electrons
3D - 5 spaces - 10 electrons
4P - 3 spaces - 6 electrons
5S -1 space - 2 electrons
4D - 5 spaces - 10 electrons
but is that all??!? what if an element has more electrons than can be fitted into these spaces? Or am I not on the right track?
Chayo
A:Yes, you are on the right track. I would replace the word "space" with "orbitals", but you seem to be okay. You could take the above list and comprise an electron configuration:
1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p6, 5s2, 4d10 --- which is a Cadmium (Cd) atom (48 electrons)
If an element that has more electrons than the above list (more than 48 electrons), you can use the periodic table to go higher. For example, Hg has 80 electrons, and it would have the following electron configuration:
1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p6, 5s2, 4d10, 5p6, 6s2, 4f14, 5d10
-Mel
i do not understand effective nuclear charge. how will (zeff) be written on the test as a question?
Can somebody explain number 7?
Effective nuclear charge will not be on the test as you think that it will. Dr. Billiot actually skipped that in class and she might not even cover it in the sense that the book does. Concentrate on what is said in class ~Kris
Could someone explain number 15 please?
Book explain it very well. Look at page 63, example 3.1, and pay attention to Fig 3.6. If you still have problem, come by my office or see me before class. Dr. Billiot
