Anonymous
Anonymous asked in Science & MathematicsChemistry · 4 weeks ago

# what is the element if the quantum numbers for the last electron has the following address n=5 l=3 ml=2 ms=-1/2?

my teacher said the answer is molybdenum but when I count to the 13th electron slot on the 5f row I keep getting nobelium

pls help

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• n = 5 is the 5th energy level

l = 3 is an f orbital

ml = 2 is one of the 7 f orbital (-3, -2, -1, 0, 1, 2, 3). The one with the 13th electron

ms = -1/2 is the spin on a single electron in this f orbital, i.e. 13th electron

Could this be Mendelevium?

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• Quantum numbers .....

n = 5, ℓ = 3, mℓ = 2, ms = -½

This describes an electron in the 5f sublevel

.....7p __ __ __

7s__

...........6d __ __ __ __ __

...................5f __ __ __ __ __ _x __

.....6p __ __ __

The element can't be molybdenum since Mo has no f-sublevel electrons.  It can't be nobelium since it has a filled 5f sublevel.

In fact the "last" electron description is troublesome because a "down spin" often indicates the second electron in an orbital, and it can't be the "last" electron because one orbital (mℓ=3) must have one electron.

If by "last" you mean the last electron to be written using the Aufbau principle, then the element would be mendelevium (Md).

It's my guess that there is some confusion with the names and symbols of molybdenum (Mo) and mendelevium (Md), and boils down to someone thinking that Md is molybdenum.

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• Nobelium is on the 7th row. Nobelium would be n = 7

• Dr W
Lv 7
4 weeks agoReport

NO NO NO.  the f orbitals are shifted down 2 rows.  Nobelium is n=5

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• The "last" electron for both Nb and Mo is the 5s1, so both have the same quantum numbers.  The difference is Nb has 4d4 orbital and Mo has a 4d5. That makes a difference in the overall electron structure but not the last electron.

• pisgahchemist
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