Can you answer these questions for me please. And explain why.
What period would 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^3 be in?? How do you figure it out?
What about the block for the same electron configuration? Why?
What would be the electron configuration for chromium??? I really need help with knowing how to do this. Please provide answers too! Thanks!
What period would 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^3 be in?? How do you figure it out?
What about the block for the same electron configuration? Why?
What would be the electron configuration for chromium??? I really need help with knowing how to do this. Please provide answers too! Thanks!
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The period is easy, it's given by the highest "n" quantum number.
For 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^3, the period would be the 4th.
For the block: find the valence electrons, in your case 4s^2 3d^3. The highest energy shell with any electrons in it is 3d, so the element is in the d block.
You might also have to know the group. Again, look at the valence electrons 4s^2 3d^3. This puts it in Group 5. (For s and d block, the group number is the number of valence electrons. For the p block, this isn't always the case. For the p block, the group number is 12 + the number of p electrons among the valence electrons.)
The electron configuration for chromium can be guessed at as follows. The atomic number is 24, therefore there are 24 electrons total. Fill them according to the "Aufbau process", that is from lowest energy to highest until you run out of electrons. The order of orbitals being filled is 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p ... You can memorize this, or use a diagram that gives you the correct order, or surmise it by looking at the periodic table. Anyway, start filling up orbitals: 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^4 and you have 24 electrons total. The d orbital is partially filled. This works for most elements...
...but unfortunately chromium is an exception because a half-filled shell is sometimes more stable. The actual configuration is 1s^2 2s^2 2p^6 3s^2 3p^6 4s^1 3d^5 where we have half-filled 4s and 3d shells. If you want an A+ on the test you'll have to memorize the exceptions, but if you're not a perfectionist don't worry about it.
For 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^3, the period would be the 4th.
For the block: find the valence electrons, in your case 4s^2 3d^3. The highest energy shell with any electrons in it is 3d, so the element is in the d block.
You might also have to know the group. Again, look at the valence electrons 4s^2 3d^3. This puts it in Group 5. (For s and d block, the group number is the number of valence electrons. For the p block, this isn't always the case. For the p block, the group number is 12 + the number of p electrons among the valence electrons.)
The electron configuration for chromium can be guessed at as follows. The atomic number is 24, therefore there are 24 electrons total. Fill them according to the "Aufbau process", that is from lowest energy to highest until you run out of electrons. The order of orbitals being filled is 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p ... You can memorize this, or use a diagram that gives you the correct order, or surmise it by looking at the periodic table. Anyway, start filling up orbitals: 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^4 and you have 24 electrons total. The d orbital is partially filled. This works for most elements...
...but unfortunately chromium is an exception because a half-filled shell is sometimes more stable. The actual configuration is 1s^2 2s^2 2p^6 3s^2 3p^6 4s^1 3d^5 where we have half-filled 4s and 3d shells. If you want an A+ on the test you'll have to memorize the exceptions, but if you're not a perfectionist don't worry about it.
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A) 4th period. Look at the S orbital, which dictates the period.
B) Block d. Transition metals are on the d block, non-metals and metalloids are on the p block, metals on the s, and f blocks are at the bottom.
C) [Ar] 4s^1 3d^5. Chromium, is an exception, it does this because this is a more stable configuration. Also what I did here is called noble gas configuration, where you place the previous noble gas (in this case Ar) in brackets, then do the rest of the configuration. It's a shortcut. So it's that piece plus everything else before Argon.
B) Block d. Transition metals are on the d block, non-metals and metalloids are on the p block, metals on the s, and f blocks are at the bottom.
C) [Ar] 4s^1 3d^5. Chromium, is an exception, it does this because this is a more stable configuration. Also what I did here is called noble gas configuration, where you place the previous noble gas (in this case Ar) in brackets, then do the rest of the configuration. It's a shortcut. So it's that piece plus everything else before Argon.