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Exceptions to the expected behavior involve elements toward the bottom of the groups. In addition to the expected ions Tl 3+ , Sn 4+ , Pb 4+ , and Bi 5+ , a partial loss of these atoms’ valence shell electrons can also lead to the formation of Tl + , Sn 2+ , Pb 2+ , and Bi 3+ ions. The formation of these 1+, 2+, and 3+ cations is ascribed to the inert pair effect    , which reflects the relatively low energy of the valence s -electron pair for atoms of the heavy elements of groups 13, 14, and 15. Mercury (group 12) also exhibits an unexpected behavior: it forms a diatomic ion, Hg 2 2+ (an ion formed from two mercury atoms, with an Hg-Hg bond), in addition to the expected monatomic ion Hg 2+ (formed from only one mercury atom).

Transition and inner transition metal elements behave differently than main group elements. Most transition metal cations have 2+ or 3+ charges that result from the loss of their outermost s electron(s) first, sometimes followed by the loss of one or two d electrons from the next-to-outermost shell. For example, iron (1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 3 d 6 4 s 2 ) forms the ion Fe 2+ (1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 3 d 6 ) by the loss of the 4 s electron and the ion Fe 3+ (1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 3 d 5 ) by the loss of the 4 s electron and one of the 3 d electrons. Although the d orbitals of the transition elements are—according to the Aufbau principle—the last to fill when building up electron configurations, the outermost s electrons are the first to be lost when these atoms ionize. When the inner transition metals form ions, they usually have a 3+ charge, resulting from the loss of their outermost s electrons and a d or f electron.

Determining the electronic structures of cations

There are at least 14 elements categorized as “essential trace elements” for the human body. They are called “essential” because they are required for healthy bodily functions, “trace” because they are required only in small amounts, and “elements” in spite of the fact that they are really ions. Two of these essential trace elements, chromium and zinc, are required as Cr 3+ and Zn 2+ . Write the electron configurations of these cations.

Solution

First, write the electron configuration for the neutral atoms:

Zn: [Ar]3 d 10 4 s 2

Cr: [Ar]3 d 5 4 s 1

Next, remove electrons from the highest energy orbital. For the transition metals, electrons are removed from the s orbital first and then from the d orbital. For the p -block elements, electrons are removed from the p orbitals and then from the s orbital. Zinc is a member of group 12, so it should have a charge of 2+, and thus loses only the two electrons in its s orbital. Chromium is a transition element and should lose its s electrons and then its d electrons when forming a cation. Thus, we find the following electron configurations of the ions:

Zn 2+ : [Ar]3 d 10

Cr 3+ : [Ar]3 d 3

Check your learning

Potassium and magnesium are required in our diet. Write the electron configurations of the ions expected from these elements.

Answer:

K + : [Ar], Mg 2+ : [Ne]

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Electronic structures of anions

Most monatomic anions form when a neutral nonmetal atom gains enough electrons to completely fill its outer s and p orbitals, thereby reaching the electron configuration of the next noble gas. Thus, it is simple to determine the charge on such a negative ion: The charge is equal to the number of electrons that must be gained to fill the s and p orbitals of the parent atom. Oxygen, for example, has the electron configuration 1 s 2 2 s 2 2 p 4 , whereas the oxygen anion has the electron configuration of the noble gas neon (Ne), 1 s 2 2 s 2 2 p 6 . The two additional electrons required to fill the valence orbitals give the oxide ion the charge of 2– (O 2– ).

Determining the electronic structure of anions

Selenium and iodine are two essential trace elements that form anions. Write the electron configurations of the anions.

Solution

Se 2– : [Ar]3 d 10 4 s 2 4 p 6

I : [Kr]4 d 10 5 s 2 5 p 6

Check your learning

Write the electron configurations of a phosphorus atom and its negative ion. Give the charge on the anion.

Answer:

P: [Ne]3 s 2 3 p 3 ; P 3– : [Ne]3 s 2 3 p 6

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Key concepts and summary

Atoms gain or lose electrons to form ions with particularly stable electron configurations. The charges of cations formed by the representative metals may be determined readily because, with few exceptions, the electronic structures of these ions have either a noble gas configuration or a completely filled electron shell. The charges of anions formed by the nonmetals may also be readily determined because these ions form when nonmetal atoms gain enough electrons to fill their valence shells.

Chemistry end of chapter exercises

Does a cation gain protons to form a positive charge or does it lose electrons?

The protons in the nucleus do not change during normal chemical reactions. Only the outer electrons move. Positive charges form when electrons are lost.

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Iron(III) sulfate [Fe 2 (SO 4 ) 3 ] is composed of Fe 3+ and SO 4 2− ions. Explain why a sample of iron(III) sulfate is uncharged.

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Which of the following atoms would be expected to form negative ions in binary ionic compounds and which would be expected to form positive ions: P, I, Mg, Cl, In, Cs, O, Pb, Co?

P, I, Cl, and O would form anions because they are nonmetals. Mg, In, Cs, Pb, and Co would form cations because they are metals.

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Which of the following atoms would be expected to form negative ions in binary ionic compounds and which would be expected to form positive ions: Br, Ca, Na, N, F, Al, Sn, S, Cd?

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Predict the charge on the monatomic ions formed from the following atoms in binary ionic compounds:

(a) P

(b) Mg

(c) Al

(d) O

(e) Cl

(f) Cs

(a) P 3– ; (b) Mg 2+ ; (c) Al 3+ ; (d) O 2– ; (e) Cl ; (f) Cs +

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Predict the charge on the monatomic ions formed from the following atoms in binary ionic compounds:

(a) I

(b) Sr

(c) K

(d) N

(e) S

(f) In

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Write the electron configuration for each of the following ions:

(a) As 3–

(b) I

(c) Be 2+

(d) Cd 2+

(e) O 2–

(f) Ga 3+

(g) Li +

(h) N 3–

(i) Sn 2+

(j) Co 2+

(k) Fe 2+

(l) As 3+

(a) [Ar]4 s 2 3 d 10 4 p 6 ; (b) [Kr]4 d 10 5 s 2 5 p 6 (c) 1 s 2 (d) [Kr]4 d 10 ; (e) [He]2 s 2 2 p 6 ; (f) [Ar]3 d 10 ; (g) 1 s 2 (h) [He]2 s 2 2 p 6 (i) [Kr]4 d 10 5 s 2 (j) [Ar]3 d 7 (k) [Ar]3 d 6 , (l) [Ar]3 d 10 4 s 2

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Write the electron configuration for the monatomic ions formed from the following elements (which form the greatest concentration of monatomic ions in seawater):

(a) Cl

(b) Na

(c) Mg

(d) Ca

(e) K

(f) Br

(g) Sr

(h) F

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Write out the full electron configuration for each of the following atoms and for the monatomic ion found in binary ionic compounds containing the element:

(a) Al

(b) Br

(c) Sr

(d) Li

(e) As

(f) S

(a) 1 s 2 2 s 2 2 p 6 3 s 2 3 p 1 ; Al 3+ : 1 s 2 2 s 2 2 p 6 ; (b) 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 3 d 10 4 s 2 4 p 5 ; 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 3 d 10 4 s 2 4 p 6 ; (c) 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 3 d 10 4 s 2 4 p 6 5 s 2 ; Sr 2+ : 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 3 d 10 4 s 2 4 p 6 ; (d) 1 s 2 2 s 1 ; Li + : 1 s 2 ; (e) 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 3 d 10 4 s 2 4 p 3 ; 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 3 d 10 4 s 2 4 p 6 ; (f) 1 s 2 2 s 2 2 p 6 3 s 2 3 p 4 ; 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6

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From the labels of several commercial products, prepare a list of six ionic compounds in the products. For each compound, write the formula. (You may need to look up some formulas in a suitable reference.)

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Questions & Answers

what is d meaning of organic chemistry
Elizabeth Reply
it's a compound that comprises of hydrocarbon
Omoru
what iz alkanol
icha Reply
alkanol there are organic compounds with the functional group of ROH and relative molecular formula (CnH2n+1+OH)
Omoru
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What's alkaline soil
Amoo Reply
a system in which only energy is transferred between the system and the surrounding is called?
Ani Reply
which Element exhibit diagonal relationship with aluminum
Ani
following processes: Solid phosphorus pentachloride decomposes to liquid phosphorus trichloride and chlorine gas b. Deep blue solid copper(II) sulfate pentahydrate is heated to drive off water vapor to form white solid copper(II) sulfate
Hisham Reply
How to know periodic table oftend
Ahmed Reply
u can know it through singing it as song it simple
Elizabeth
how to get atomic number of an element
Ogunleye Reply
how do you solve the examples in a much more explanatory way
Ogunleye
it seems by multiplying d number of d element by 2
Elizabeth
E.g like carbon 6*2=12 so d atomic number is 12
Elizabeth
The reaction of aceto nitrile with propane in the presence of the acid
Explain this paragraph in short
Manish Reply
What is solid state?
Manish Reply
What is chemical reaction
Manish
transforming reactants to product(s)
Andre
process
Andre
solid state is composed of tightly particles and it has a definite shape and volume
Elizabeth
Example of Lewis acid
Chidera Reply
Example of Lewis acid
Chidera
Chlorine
Mikidad
Anything with an empty orbital... the hydrogen ion is the most common example. BH3 is the typical example, but any metal in a coordination complex can be considered a Lewis acid.
Eszter
okay thanks
Jovial
aluminium and sulphur react to give aluminium sulfide.How many grams of Al are required to produce 100g of aluminium sulphide
Soni Reply
aluminium and sulphur react to give aluminium sulphide how many grams of Al are required to produce 100g of aluminium sulphide?
Soni
aluminium and sulphur react to give aluminium sulphide how many grams of Al are required to produce 100g of aluminium sulphide?
Soni
2Al+3S=Al2S3
galina
m(Al)=100×27×2/150=36g
galina
150 comes from?
Soni
thank you very much
Soni
molar mass of Al2S3
galina
150.158
thiru
Why can't atom be created or destroyed
Jacaranda Reply
matter simply converts to pure energy
that's nice
Meshach
explain how to distinguish ethanol from a sample of ethanoic acid by chemical test
Alice Reply
explain how ethanol can be distinguished from ethanoic acid by chemical test
Alice
Using a suitable experiment, describe how diffusion occurs in gases.
Melody Reply
when the excited energy which are in gaseous state collides with another to liberate from one place to another
Meshach
Practice Key Terms 2

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Source:  OpenStax, Chemistry. OpenStax CNX. May 20, 2015 Download for free at http://legacy.cnx.org/content/col11760/1.9
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