answer to ADA question about electron configuration

[jaerob]

Hey guys-

Here is a question from the practice test in the ADA registration booklet ==>

"The electronic configuration of a particular neutral atom is 1s2 2s2 2p6 3s2 3p2. What is the number of unpaired electrons in this atom?"

Now, unless I'm smoking something really awesome, this is the electron configuration for Si and has 4 unpaired valence electrons, right? However, the ADA solution says that the correct answer is 2 unpaired electrons. Am I having a huge brain fart or is the ADA answer wrong?

Thanks in advance for any backup or explanation to why I'm wrong.. I hate all the wrong answers in all of these practice tests (Kaplan, Barrons, etc)...

-Jae-

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[dat_student]

Hey guys-

Here is a question from the practice test in the ADA registration booklet ==>

"The electronic configuration of a particular neutral atom is 1s2 2s2 2p6 3s2 3p2. What is the number of unpaired electrons in this atom?"

Now, unless I'm smoking something really awesome, this is the electron configuration for Si and has 4 unpaired valence electrons, right? However, the ADA solution says that the correct answer is 2 unpaired electrons. Am I having a huge brain fart or is the ADA answer wrong?

Thanks in advance for any backup or explanation to why I'm wrong.. I hate all the wrong answers in all of these practice tests (Kaplan, Barrons, etc)...

-Jae-

Where did you get the ADA registration booklet? I have called ADA a numer of times and they keep telling me that they don't give out the questions anymore. Can someone please scan these sample questions and put it up for everyone @SDN. I think these questions will be helpful for all of us.

 

[dat_student]

Hey guys-

Here is a question from the practice test in the ADA registration booklet ==>

"The electronic configuration of a particular neutral atom is 1s2 2s2 2p6 3s2 3p2. What is the number of unpaired electrons in this atom?"

Now, unless I'm smoking something really awesome, this is the electron configuration for Si and has 4 unpaired valence electrons, right? However, the ADA solution says that the correct answer is 2 unpaired electrons. Am I having a huge brain fart or is the ADA answer wrong?

Thanks in advance for any backup or explanation to why I'm wrong.. I hate all the wrong answers in all of these practice tests (Kaplan, Barrons, etc)...

-Jae-

As written, only the 2 electrons in 3p are unpaired.

 

[dentalengineer]

Call ADA and ask them to send you an application. Sample test is attached to the application.

 

[mochafreak]

Hey guys-

Here is a question from the practice test in the ADA registration booklet ==>

"The electronic configuration of a particular neutral atom is 1s2 2s2 2p6 3s2 3p2. What is the number of unpaired electrons in this atom?"

Now, unless I'm smoking something really awesome, this is the electron configuration for Si and has 4 unpaired valence electrons, right? However, the ADA solution says that the correct answer is 2 unpaired electrons. Am I having a huge brain fart or is the ADA answer wrong?

Thanks in advance for any backup or explanation to why I'm wrong.. I hate all the wrong answers in all of these practice tests (Kaplan, Barrons, etc)...

-Jae-

You're not answering their question...it has 4 valence electrons. But, like dat student said only the electrons in the 3p2 are unpaired. It's a question about m_s (the electron spin quantum number) and Hund's Rule.

 

[psiyung]

You're not answering their question...it has 4 valence electrons. But, like dat student said only the electrons in the 3p2 are unpaired. It's a question about m_s (the electron spin quantum number) and Hund's Rule.

The 3s2 and the 3p2 electrons form the valence electrons in this particular element. But realize that only the 3p2 electrons are unpaired. Note that having paired electrons does NOT mean that they cannot be involved in bonding

 

[jaerob]

The 3s2 and the 3p2 electrons form the valence electrons in this particular element. But realize that only the 3p2 electrons are unpaired. Note that having paired electrons does NOT mean that they cannot be involved in bonding

Hahaha, true true. I feel quite stupid Thanks all!

 

[jaerob]

Where did you get the ADA registration booklet? I have called ADA a numer of times and they keep telling me that they don't give out the questions anymore. Can someone please scan these sample questions and put it up for everyone @SDN. I think these questions will be helpful for all of us.

As Dentalengineer mentioned, the practice test is attached to the DAT registration booklet. You can either call them and ask them to send it to you, or your school's health professions office should have them lying around (that's where I picked mine up)