Chemistry CLEP question

braithiar · Jul 12, 2009

The electron configuration given shows that element X (which is phosphorus, but that's not important) has 3 electrons in its outermost subshell (3p) and a total of 5 electrons in its valence shell (3s2 + 3p3). Element X will likely want to acquire 3 more electrons to fill this outer shell to put it in a stable state. Mg on the other hand wants to get rid of 2 electrons to become stable. So now you have Mg2+ & P3-. Balance these to get your answer: you need 3 Mg to negate the negative P charges and 2 P to negate the Mg positive charges (3*2 = 6; 2 * -3 = -6; -6+6 = 0).

Hope this helps! If not let me know.

CrufflerJJ, BSN, RN, EMT-P · Jul 12, 2009

Hi-
I am in the process of studying for the Chemistry CLEP exam and need help on one of the questions. The question is:
1s2 2s2 2p6 3s2 3p3
Atoms of an element, X, have the electronic configuration shown above. The compound most likely formed
with magnesium, MG, is
a. MgX
b. Mg2X
c. MgX2
d. Mg2X3
e. Mg3X2
The answer is E. Can anyone explain why the answer is E??
Thanks,
Jen

Here's my guess (based on 20 year old chemistry classes, so be forewarned!):

Magnesium is a Group II element, and normally has a +2 ionic charge so let's call it Mg+2.

Element X will have a -3 ionic charge since the last orbital (3p3) is only partially filled by the 3 electrons. Each electron could contribute a -1 charge, for a total of -3 per atom of element X.

The +'s & the -'s need to balance out in a compound composed of Mg & X. Since Mg has a +2 charge, and X has a -3 charge, the lowest number of atoms of each that will result in a neutrally charged compound is 3 atoms of Mg, combined with 2 atoms of X.

3 * (+2) + 2* (-3) = 0

Final compound would be Mg3X2.

I hope.

sleepyRN2 · Jul 12, 2009

the X element having an atomic configuration of 1s2 2s2 2p6 3s2 3p3 has an outer p orbital which is not filled, i.e. 3p3, compare it to the next but lower p-orbital which is 2p6, notice that this one is filled, because the p orbitals can accommodate, at the most, 6 electrons. Therefore with a 3p3, X element is able to accept three more electrons to satisfy the requirement, i.e. to attain the most stable isoelectronic configuration to that of its nearest noble (inert) atom. Consequently, X atom having filled by 3 electrons into its outer most p orbital becomes an anion, X 3-. X3- in turn can form, say, an ionic bond with Mg2+ (a cation) to yield Mg3X2.

or Mg2+ (aq) + X3- (aq) --> Mg3X2 (s)

Therefore, e) Mg3X2 is the correct choice.

sleepyRN2 · Jul 12, 2009

remember only the outer most (valence) electrons are involved in any type of bonding. so it's important that you look at the highest principal number and its suborbitals of any electronic configuration to figure out what's going on or rather what will go on. hope this helps you.

zuzi · Jul 13, 2009

1. Because you have 3 electrons on incomplete comfiguration on 3p3, instead to have 3p6 that is a complete configuration. SOOOO 3 is the valence of your unknown element X. The valence of Mg is 2. To make a substance the theory tell you that the valence of first element Mg (2) is going to second and the valence to second element X (3) is going to the first... result....Mg3X2....easyyyyyyyyyy!

NOW my question for your beuatifull smart mind chemistry teacher, ask her WHAT REAL substance with this configuration she knows and what is the name of it, LOOOOOOL...if she dosen't know tell her to share the CHEMISTRY dicipline and paycheck with Zuzi, lol

sleepyRN2 · Jul 13, 2009

Magnesium nitride can be produced by burning magnesium metal in a pure nitrogen atmosphere.

3 Mg + N2 → Mg3N2

MAGNESIUM PHOSPHIDE

Trimagnesium diphosphide

Mg3P2

Magnesium orificenide (Mg3As2)

Magnesium antimonideMolecular Formula: Mg3Sb2

sleepyRN2 · Jul 13, 2009

polyanion w/ Mg2+

Mg3(PO4)2

CrufflerJJ, BSN, RN, EMT-P · Jul 13, 2009

Magnesium nitride can be produced by burning magnesium metal in a pure nitrogen atmosphere.
3 Mg + N2 → Mg3N2

What's fun to do is to burn magnesium in a regular atmosphere. You get a mixture of Mag oxide + Mag nitride. Take that white ash, add some water, and ammonia is generated. Pretty neat! Better living through chemistry.

zuzi · Jul 14, 2009

Here you are, here you are....not bad at all! If is from your mind is good, if is from google..IS BAD! lol

sleepyRN2 · Jul 14, 2009

this is quite easy, it's the VA group in the period table, basic chemistry that any serious chemist ought to know. however, i don't see the reason for mocking google, a reference is a reference; google is widely used source and evolving; and as one uses google more, it helps in enabling the user and proprietors in enhancing the credibility and substance of the source (google). i have had excellent chemistry professors as an undergrad in biochemistry, btw, are fairly known published (bio)chemists who extolled the great virtue of using references so long as they are reputable. caveat emptor, everybody.

zuzi · Jul 14, 2009

Physics chemistry and mathematics...always was low points for nurses....lol, is just a true, unfortunatelly a real one. Is much more than a pleasure to know that is someone with chemistry background, lol, and a nurse by the way! Nice to meet you!