Can someone explain??

[Predentknight]

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#1) The electronic configuration of a particular neutral atom is 1s^2 2s^2 2p^6 3s^2 3p^6 3d^6 4s^2. The number of unpaired electrons in the atom is...

A. 0
B. 1
C.2
D. 4
E.6


Ans. is D. , can someone explain this, it gets me everytime

#2) This is just a question I have and if someone can explain that would be great. Why is the evaporation of rubbing alcohol accompanied by increase in Entropy.

I would think that the deposition of carbon dioxide would be accompanied by an increase in entropy, but apparently I am wrong.

 

[idyke]

the 6 electrons in d subshell would be distributed among 5 orbitals, and applying Hund's law, (↑&#8595😉(&#8593😉(&#8593😉(&#8593😉(&#8593😉

4s has only one orbital thus its 2 electrons would be paired.

And Entropy increases from solid -> liquid -> gas. It's a quality of disorder, so solids are the most organized (=less entropy), whereas the gas which is very free, is the least organized, thus greater entropy.

 

[creative8401]

Hi Predentknight. The first one is a bit tricky, but lets take a look.

1) This question deals with the building up principle. According to the Pauli Exclusion principle, no two electrons can have the same set of 4 quantum numbers. The S orbitals can accomodate a maximum of two electrons, and the P orbitals can accomodate a maximum of 6 electrons. When we are in the 4S orbital, which corresponds to the 4th period in the periodic table, there is a subshell known as the 3D orbitals. Please note that the D orbitals can hold a maximum of 10 electrons.

Now lets go back to the electron configuration you have (we should be interested in its ending), which is 3d^6 4s^2. Thus this means that the S orbital contains two electrons, which is a full orbital. Since the D orbitals can hold a max of 10 electrons, and we only have 6, it gives us a difference of 4. Hence your answer D.

2) Entropy can be defined as an increase in disorder in the universe. For example, when a solid forms a gas, the molecules within a gas are in a random, rapid crazy like motion compared to the finely structured design of a solid. The rubbing alcohol, which is a liquid, has a defined surface area and volume. Even though it takes the shape of the container it is in, its molecules are in a more structured design. When the molecules evaporate, they are in chaotic motion compared to the molecules within a liquid. Remember, as we go form solid to liquid to gas, the entropy (disorder pertaining to the molecules) increases.

 

[Predentknight]

wow thank you both for these responses. It really helped out. For some reason I was thinking the D orbital was 10 orbitals but now i understand it is 5 orbitals that hold 10 electrons.. stupid me.

As far as the other question goes I just want to make sure that I have this straight. Ok since rubbing alcohol is going from liquid to gas it would possess the most entropy. Deposition of a gas to a solid would give the least entropy because ssolid is in a very ordered state. Think I got it now, what an amazing resource this is, thank you all.

 

[Zerconia2921]

#1) The electronic configuration of a particular neutral atom is 1s^2 2s^2 2p^6 3s^2 3p^6 3d^6 4s^2. The number of unpaired electrons in the atom is...

A. 0
B. 1
C.2
D. 4
E.6


Ans. is D. , can someone explain this, it gets me everytime

#2) This is just a question I have and if someone can explain that would be great. Why is the evaporation of rubbing alcohol accompanied by increase in Entropy.

I would think that the deposition of carbon dioxide would be accompanied by an increase in entropy, but apparently I am wrong.

Alright your first question: Focus only on the valence electrons which are the outter most e-. The outter most e- consist of the 4s^2 3d^6 . The electrons will fill the lowest energy level first. We should know which one is the lowest energy level and highest to do this we do the following.

Between the 4s and 3d orbitals which one is smaller? 4 s = 4+ 0 = 4 (s orbital 0, p orbital 1, d orbital 2) So 3d = 3+2 = 5 4<5 therefore the 4s fills first then the 3d will fill second this also means that the 3d orbital electrons will be removed first.

The d orbital when diamagnetic (filled) would have a total of 10 electrons who occupied in each orbital. The 3d^6 orbital had 5 orbitals that 2 e- can occupy if you have 6 e- four orbitals will be paramagnetic and one will be diamagnetic.

Question 2)
If you remember from bio lab during disection we sprayed alcohol on the counter tops as a disenfect. As we sprayed the alcohol it would later evaporated right in front of our eyes. Thus, from its liquid state it evaporated into the gaseus phase. Entropy is the second law of thermodynamics, which basicly says the universe tends to approch a disorder state. When alcohol was in its liquid state the molecules were ordered but when in the gases state the spread apart from one another and increased in disorder.