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ChemWiki: The Dynamic Chemistry E-textbook > Under Construction > Delmar > Introduction to Elements > Metals and Nonmetals and Their Ions

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Metals and Nonmetals and Their Ions

At some point in life, you stumble across the words metals and nonmetals, whether in the middle of a conversation about rusty bike fenders or as vocabulary terms in a science textbook in fifth grade, and think to yourself, “metal, like copper, conducts electricity, and nonmetal, like wood, does not.” You might have some general conceptions about metals and nonmetals from personal experience, but there are several more characteristics that contribute to their own uniqueness. On the periodic table, the elements can be divided into two broad categories: metals and nonmetals. There are also subgroups in each category that further accounts for all the properties of the elements.

Properties of Metals and Nonmetals

Metal characteristics include luster, heat and electricity conductivity, malleability (ability to bend instead of crumble), ductility (ability to be shaped or molded), and high melting point. Also, metals are usually reducing agents with lower electronegativities. Metal oxides form a base when they react with water:

\[K_2O\,(s) + H_2\, (l) \rightarrow 2K^+\, (aq) + 2OH^-\, (aq) \]

 (nonmetal oxide)                (acid)

Nonmetals display dullness, poor heat and electricity conductivity, brittleness (crumble instead of bend), and exist mostly in the liquid or gas form due to lower density and melting points. They are also good oxidizing agents and usually have higher electronegativities. Nonmetal oxides form an acid when they react with water:

\[  SO_3\,(g) + H_2O\, (l) \rightarrow H_2SO_4\, (aq) \]

 (nonmetal oxide)                (acid)

The Periodic Table

periodic table.jpg
Subgroup Definition/Location
Metals
Alkali Metals

series of very reactive metals

group 1 on periodic table (with the exception of Hydrogen)

Alkaline Earth Metals

series of reactive metals (less reactive than alkali metals)

group 2 on periodic table

Transition Metals

series of elements that exhibit characteristics of metals, though less reactive and less metallic than the first two groups of metals

groups 3 - 12 on periodic table

Metalloids - elements that exhibit metallic characteristics as well as some nonmetallic characteristics, such as reactivity (whether as metal or nonmetal) depending on which element it's reacting with

ex: Silicon has a metallic luster but is not a good electricity conductor

groups 13 - 16, but only the highlighted ones next to stair steps on periodic table

Nonmetals
Halogens

series of elements that are most reactive for nonmetals due to their near-stable electron configuration (a valence shell of 7 electrons)

group 17 on periodic table

Noble Gases

series of elements that are inert (nonreactive) due to stable electron configuration (a full valence shell of 8 electrons)

group 18 on periodic table

Ions of Metals and Nonmetals

Ions: An atom or group of atoms gain an electric charge by gaining or losing an electron, usually through bonding. Cation: An atom loses electrons and is positive   ex: Ca2+. Anion: An atom gains electrons and is negative   ex: Cl-.

Metals usually form cations while Nonmetals usually form anions.

All elements on the periodic table (with the exception of noble gases) strive for one of the following more-stable electron configurations:

  1. noble gases' electron configuration with a full valence shell of 8 electrons   ex: F - = [Ne] 3s2 3p6
  2. electron configuration of half-full or full d-orbital in the case of transition metals   ex: Ag+ = [Kr] 5s14d105p6

Ions of Periodic Groups

Group/Name Characteristics of Ion
Group 1/Alkali Metals

Noble gas' electron configuration - Loses one electron to have a charge of +1

*Also applies to Hydrogen (H+) even though it's not an alkali metal

Group 2/Alkaline Earth Metals Noble gas' electron configuration - Loses two electrons to have a charge of +2
Groups 3-12/Transition Metals

Electron configuration with half-full or full d-orbital

A few transition metals form two ions, and it's best to just know them: Copper (Cu+ & Cu2+) Iron (Fe2+ & Fe3+), Mercury (Hg& Hg2+), and Tin (Sn2+ & Sn4+)

 A few transition metals have a specific ion despite the number of valence electrons: Chromium (Cr3+), Nickel (Ni2+), Silver (Ag+), Zinc (Zn2+)

Group 13

These elements often choose between losing and gaining electrons to get to noble gas' electron configuration (they can go either way)

* Aluminum is an exception: Al3+

Group 14

These elements can lose a different number of electrons to achieve stability

ex: Sn can lose 2 electrons to get a full s-orbital or 4 electrons to get to noble gas' electron configuration

* Lead can only be Pb2+

Group 15 Noble gas' electron configuration - gains 3 electrons to have a charge of -3
Group 16 Noble gas' electron configuration - gains 2 electrons to have a charge of -2
Group 17/Halogens Noble gas' electron configuration - gains 1 electron to have a charge of -1
Group 18/Noble gases No ion due to existing stable electron configuration of 8 valence-shell electron

Properites of Metals and Nonmetals when they bond

1. Ionic bonds takes place when there's a nonmetal and a metal that exchange electrons.

\[  Na^+ + Cl^-  = NaCl\]

 Metal + Nonmetal = Ionic

2. Covalent bonds are when electrons are shared between two nonmetals.

\[ H_2 + 2F^- =  2HF \]

Nonmetal + Nonmetal = Covalent

In a bond, the charge each element/molecule in a chemical reaction carries over to the element/molecule it is bonding to.

\[ Ca^{2+} + 2NO_3^- = Ca(NO_3)_2 \]

The charge of 2+ from the calcium carries over to the NO3 and the charge of 1- from nitrate carries over to   the Ca. 

Practice Problems

Apply knowledge about ions to write the following compounds

1) Ca & Cl

Answer: CaCl2 (Ca2+ + 2Cl-)

2) Fe & S

Answer: Fe(II)S (Fe2+ + S2-)

Apply knowledge about Ions to write oxidation state of the following

1) C2O42-

Answer:     O - O.S. of -2                C - O.S. of +3

(4x -2 charge of O4 is -8, but this polyatomic ion has an overall charge of -2, which means C2 has a charge of +6, which gives C a charge of +3) ---> (2 x +3)+(4 x -2) = 6 - 8 = -2, which is overall charge of the ion

2) HCO3-

Answer:    O - O.S. of -2                H - O.S. of +1               C - O.S. of 4+

(3x -2 charge of O3 is -6; H has charge of +1 so it becomes -5, but this anion has an overall charge of -1, which gives C a charge of 4+) ---> (1 x +1)+(1 +4)+(3 x -2) = 1 + 4 - 6 = -1, which is overall charge of the ion

Apply knowledge about oxides to determine whether the product will be an acid or a base

1) MgO + H2O ---->

Answer:     product will be a base because MgO is a metal oxide

MgO + H2O ----> Mg2+ + 2OH-

2) SO2 + H2O ---->

Answer:    product will be an acid because SO2 is a nonmetal oxide

SO2 + H2O ----> H2SO3

References

  1. Petrucci, Ralph H., William S. Harwood, F. G. Herring, and Jeffry D. Madura. General Chemistry: Principles and Modern Applications. 9th ed. Upper Saddle River: Pearson Education, Inc., 2007.
  2. Brown, Theodore E., Bruce D. Bursten, H. Eugene Lemay. Chemistry: The Central Science. 10th ed. Upper Saddle River: Pearson Education, Inc., 2006.
  3. Metals and Nonmetals, HyperPhysics., <http://hyperphysics.phy-astr.gsu.edu...tab/metal.html>.

Outside Links

  1. Reference for Characteristics of Nonmetals
  2. Reference for Characteristics of Metals
  3. Reference for Characteristics of Metalloids

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08:17, 14 Dec 2013

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