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Beginning with the transition metal scandium (atomic number 21), additional electrons are added successively to the 3 d subshell. This subshell is filled to its capacity with 10 electrons (remember that for l = 2 [ d orbitals], there are 2 l + 1 = 5 values of m l , meaning that there are five d orbitals that have a combined capacity of 10 electrons). The 4 p subshell fills next. Note that for three series of elements, scandium (Sc) through copper (Cu), yttrium (Y) through silver (Ag), and lutetium (Lu) through gold (Au), a total of 10 d electrons are successively added to the ( n – 1) shell next to the n shell to bring that ( n – 1) shell from 8 to 18 electrons. For two series, lanthanum (La) through lutetium (Lu) and actinium (Ac) through lawrencium (Lr), 14 f electrons ( l = 3, 2 l + 1 = 7 m l values; thus, seven orbitals with a combined capacity of 14 electrons) are successively added to the ( n – 2) shell to bring that shell from 18 electrons to a total of 32 electrons.

Quantum numbers and electron configurations

What is the electron configuration and orbital diagram for a phosphorus atom? What are the four quantum numbers for the last electron added?


The atomic number of phosphorus is 15. Thus, a phosphorus atom contains 15 electrons. The order of filling of the energy levels is 1 s , 2 s , 2 p , 3 s , 3 p , 4 s , . . . The 15 electrons of the phosphorus atom will fill up to the 3 p orbital, which will contain three electrons:

This figure provides the electron configuration 1 s superscript 2 2 s superscript 2 2 p superscript 6 3 s superscript 2 3 p superscript 3. It includes a diagram with two individual squares followed by 3 connected squares, a single square, and another connected group of 3 squares all in a single row. The first square is labeled below as, “1 s.” The second is similarly labeled, “2 s.” The first group of connected squares is labeled below as, “2 p.” The square that follows is labeled, “3 s,” and the final group of three squares is labeled, “3 p.” All squares except the last group of three squares has a pair of half arrows: one pointing up and the other down. Each of the squares in the last group of 3 contains a single upward pointing arrow.

The last electron added is a 3 p electron. Therefore, n = 3 and, for a p -type orbital, l = 1. The m l value could be –1, 0, or +1. The three p orbitals are degenerate, so any of these m l values is correct. For unpaired electrons, convention assigns the value of + 1 2 for the spin quantum number; thus, m s = + 1 2 .

Check your learning

Identify the atoms from the electron configurations given:

(a) [Ar]4 s 2 3 d 5

(b) [Kr]5 s 2 4 d 10 5 p 6


(a) Mn (b) Xe

Got questions? Get instant answers now!

The periodic table can be a powerful tool in predicting the electron configuration of an element. However, we do find exceptions to the order of filling of orbitals that are shown in [link] or [link] . For instance, the electron configurations (shown in [link] ) of the transition metals chromium (Cr; atomic number 24) and copper (Cu; atomic number 29), among others, are not those we would expect. In general, such exceptions involve subshells with very similar energy, and small effects can lead to changes in the order of filling.

In the case of Cr and Cu, we find that half-filled and completely filled subshells apparently represent conditions of preferred stability. This stability is such that an electron shifts from the 4 s into the 3 d orbital to gain the extra stability of a half-filled 3 d subshell (in Cr) or a filled 3 d subshell (in Cu). Other exceptions also occur. For example, niobium (Nb, atomic number 41) is predicted to have the electron configuration [Kr]5 s 2 4 d 3 . Experimentally, we observe that its ground-state electron configuration is actually [Kr]5 s 1 4 d 4 . We can rationalize this observation by saying that the electron–electron repulsions experienced by pairing the electrons in the 5 s orbital are larger than the gap in energy between the 5 s and 4 d orbitals. There is no simple method to predict the exceptions for atoms where the magnitude of the repulsions between electrons is greater than the small differences in energy between subshells.

Questions & Answers

what is measurement
Isaiah Reply
is the comparison of an unknown quantity with a fixed quantity of the same kind
How does an element differ from a compound? How are they similar?
Adeola Reply
an element is an indivisible particles that can take part in a reaction and consist of smaller or tiny particles i.e proton, neutrons and electron while a compound is when two or more element chemically combine together. They are similar when they are homogeneous compound. they take the same rxn.
How to get the Lewis formula of SeCl+3
Erica Reply
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what is the structural formula for starch
EZEA Reply
Starch is a mixture (of chemicals) of amylose and amylopectin. Both are macromolecules and polymers. You can search on wikipedia.
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what is the roles of Alu m
what is the roles of chlorine
Roles can be classified or correlate it to different areas: For example: Chlorine can be used in reactions (in industry) to manufacture HCl, which then can be used for other things. Or in swimming pools to kill bacteria. Or as a component in compounds with pharmaceutical roles (drugs). For Al:
Its dentisty value is suitable to be used in alloys (mixture of metals) in aircraft bodies. Also, Aluminium foils, Tin cans,.. Some of them are also in Al overhead cables in streets and long roads.
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Yushao Reply
it is an adverb which means extremely
what is atomic chemistry?
Gladys Reply
Lewis structure for no3
Lewis structure for no3
what is weak acid
Muhammed Reply
It is an acid which partially ionises in water.
what is incandescence
what makes it glow
why is it red, irange and yellow in color
hello am new here and I want to join you
hello i am new here please i want to join this group
Hi, I'm also new here
hello guys !!
what is pressure?
Slark Reply
The force applied to suction Area of the body
Matter composed of exceedingly small paticle called atom.
questions related to metals
Regina Reply
occurrence and preparation of the representatives metals
list the 20, periodic table and their symbols
Fathmat Reply
hydrogen:h helium;he lithium:l beryllium:be Boron:b Carbon;C Nitrogen:n Oxygen:O FLUORINE:f Neon:n Sodium:s Magnesium:mg Aluminum:a Silicon:s Phosphorus:p Sulphur:s Chlorine:c Argon;a Potassium:p Calcium:c
Hydrogen, helium, lithium, beryllium, boron, carbon, nitrogen, oxygen, fluorine, neon, sodium, magnesium, aluminium, silicon, phosphorus, sulphur, chlorine, argon, potassium, calcium
what is a solute
Ekezie Reply
Any substance that is disolved in a liqid solvent to create a solution
sorry liquid
it's a liquid substance
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is the substance that dissolves in the solvent
so is HCl ionic compound
Honest Reply
No, covalent compound ➡️ molecule. As both H and Cl are non-metals and and form covalent bind by sharing valence e-. But can fully ionice in water forming H+ (a proton, a reason for acidity) and Cl- (anion =Chloride) Hydrogen Chloride is a gas at room; Hydrochloric acid = HCl (aq), dissolved in w
Form covalenr bond*
The question marks are an emoji in the first sentence is an unread emoji. HCl Covalent compund -> molecule
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Chukwu Reply
is the study of composition of substances and the way they behave under different conditions
how do calculate n1 though n6 any help on understanding the concept
where can I get the test bank or mcqs ? any idea ?
Sourav Reply
what are the types of intermolecular forces between organic compounds
Eke Reply
Intermolecular forces exist between molecules of different units like van der waal force, hydrogen bonds
Practice Key Terms 7

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