chemical bonding - important concepts in inorganic chemistry

8/8/2019 Chemical Bonding - Important Concepts in Inorganic Chemistry

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Chemical Bonding.Unions that build


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Atoms tend to gain, lose or share electrons

so as to have eight electrons in their outerelectron shell giving them the same electronicconfiguration as a noble gas.

The rule is applicable to the main-groupelements, especially carbon, nitrogen,oxygen, and the halogens, but also to metalssuch as sodium or magnesium.

In simple terms, molecules or ions tend to bemost stable when the outermost electronshells of their constituent atoms contain eight

electrons.
http://en.wikipedia.org/wiki/Noble_gashttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Nitrogenhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Halogenshttp://en.wikipedia.org/wiki/Sodiumhttp://en.wikipedia.org/wiki/Magnesiumhttp://en.wikipedia.org/wiki/Magnesiumhttp://en.wikipedia.org/wiki/Sodiumhttp://en.wikipedia.org/wiki/Halogenshttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Nitrogenhttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Noble_gas


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The octet rule does not work for predicting thecharges on transition metals ions.

Transition metals are located on the periodic table

in the ten columns between columns for therepresentative elements, and the groups arelabeled IB to VIIIB.

The transition metals typically produce ions with1+, 2+, 3+ and sometime 4+ charges, and unlikethe representative elements many transitionmetals can have more than one charge state


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Valence electrons: Electrons in the outermostelectron shells, maximum 8 electrons. noblegases has 8 electrons

Ion: A charged atom. Can be either positive ornegative. Positive ion: Is an atom that lost at least one

electron, are called cations. Example Na+

, Mg2+

, Al3+

Negative ion: Is an atom that gained at least oneelectron, are called anions. Cl-, O2-, N3-


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Groups IA, IIA, and IIIA have metallic atomsthat tend to lose electrons to acquireelectronic configuration of a noble gasforming positive ions.

Groups VA, VIA, VIIA have non metallic atomsthat tend to gain electrons to acquire

electronic configuration of a noble gasforming negative ions.


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Element Group Valence e- Electrons to formIon IonFormedLost GainedSodium IA Na+

Magnesium IIA Mg2+

Calcium IIA Ca2+

Aluminum IIIA Al3+

Sulfur VIA S2-

Oxygen VIA O2-

Chlorine VIIA Cl-

Bromine VIIA Br-


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Lewis structures, also called Lewis-dotdiagrams, Electron-dot diagrams or Electron-dot structures, are diagrams that show thebonding between atoms of a molecule, and

the lone pairs of electrons that may exist inthe molecule.

Consists of the element symbol surrounded

by "dots" to represent the number ofelectrons in the outer energy level (correlatedby the Group number).


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However, because of the high chargethat would result, either C4+ or C4- forcarbon and Si4+ or Si4- for silicon


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Lithium Calcium

Aluminum

Carbon

Nitrogen Oxygen

Chlorine

Argon

Lithium ion Calcium ion Aluminum ion Carbon

Nitrogen ion Oxygen ion Chlorine ion Argon


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Symbol AtomicElectronicconfigurationLewisatomstructure

Formedion Ionic Electronicconfiguration LewisionicstructureLi 1s2 2s1 Li Li+ 1s2 Li+

Be

B

C

N

OF

Ne


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A chemical bond is the attraction caused bythe electromagnetic force between opposingcharges, either between electrons and nucleior as the result of a dipole attraction.

The strength of bonds varies considerably;there are "strong bonds" such as covalent orionic bonds and "weak bonds" such asdipole-dipole interactions, the Londondispersion force and hydrogen bonding.
http://en.wikipedia.org/wiki/Covalent_bondhttp://en.wikipedia.org/wiki/Ionic_bondhttp://en.wikipedia.org/wiki/Intermolecular_forcehttp://en.wikipedia.org/wiki/London_dispersion_forcehttp://en.wikipedia.org/wiki/London_dispersion_forcehttp://en.wikipedia.org/wiki/Hydrogen_bondinghttp://en.wikipedia.org/wiki/Hydrogen_bondinghttp://en.wikipedia.org/wiki/London_dispersion_forcehttp://en.wikipedia.org/wiki/London_dispersion_forcehttp://en.wikipedia.org/wiki/Intermolecular_forcehttp://en.wikipedia.org/wiki/Ionic_bondhttp://en.wikipedia.org/wiki/Covalent_bond


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Type of chemical bond that involves a metal and

a nonmetal ion through electrostatic attraction. Itis a bond formed by the attraction between twooppositely charged ions, The electrostaticattraction between the oppositely charged ionscauses them to come together and form a bondlike magnets .

The metal donates one or more electrons,forming a positively charged ion or cation with a

stable electron configuration. These electronsthen enter the non metal, causing it to form anegatively charged ion or anion which also has astable electron configuration.
http://en.wikipedia.org/wiki/Nonmetalhttp://en.wikipedia.org/wiki/Ionhttp://en.wikipedia.org/wiki/Electrostatichttp://en.wikipedia.org/wiki/Metalhttp://en.wikipedia.org/wiki/Nonmetalhttp://en.wikipedia.org/wiki/Ionhttp://en.wikipedia.org/wiki/Electrostatichttp://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/Cationhttp://en.wikipedia.org/wiki/Cationhttp://en.wikipedia.org/wiki/Electron_configurationhttp://en.wikipedia.org/wiki/Cationhttp://en.wikipedia.org/wiki/Electron_configurationhttp://en.wikipedia.org/wiki/Anionhttp://en.wikipedia.org/wiki/Anionhttp://en.wikipedia.org/wiki/Anionhttp://en.wikipedia.org/wiki/Electron_configurationhttp://en.wikipedia.org/wiki/Cationhttp://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/Electrostatichttp://en.wikipedia.org/wiki/Ionhttp://en.wikipedia.org/wiki/Nonmetalhttp://en.wikipedia.org/wiki/Metal


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For example, common salt is sodium chloride.When sodium (Na) and chlorine (Cl) are combined, thesodium atoms each lose an electron forming a cation(Na+), and the chlorine atom gain an electron to forman anion (Cl).

Na + Cl Na+ + Cl-


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Formed between a metallic element and a nonmetallic element.

The bonding involves electrons transfer, themetal atom donates electrons while the non

metal accept the electrons. The compounds formed are solids with a

crystal lattice tridimensional structure.

Most of them dissolve in water givingsolutions that conducts electricity

Salts (NaCl) and acids (HCl) are ioniccompounds


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1. Find the total number of electrons:For each atom, read the group number.

2. Draw a first tentative structure:The element with the least number of atoms is usually thecentral element. Draw a tentative molecular and electronarrangement attaching other atoms with single bonds as the firstguess.

3. Add electrons as dots to get octets around atoms:When counting electrons for the octet around an atom, countboth electrons in a bond for each atom and any lone pairelectrons. Hydrogen, of course, gets only 2 electrons.

4. Count the total number of electrons in the final structure tosee if the total agrees with the number tabulated in step #1. If

not, then move a lone pair of electrons into a double bond. Oradd more lone pairs of electrons.

5. Cycle through steps 3 and 4 several times until you get it rightby trial and error.


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NaCl Na IA = 1e Cl VIIA= 7e

Na + Na+

MgCl2

Mg IIA=2e Cl VIIA= 7e

Mg + Mg2+

RbBr

CaBr2AlF3SrO

Cl

Cl -

Cl

Cl

Cl -

Cl -


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Chemical bonding is characterized by thesharing of pairs of electrons between atoms.

Is formed by at least two non-metallic

elements, they can be molecules of the sameatom like O2 or different atoms like H2O.

The atoms can share more than one pair of

electrons, they can share two or even threepair of electrons, like single, double or triplebonds.


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or

The pair of shared electronscan be drawn with lines

Cl Chlorine molecule Cl2Cl = 7 e

Cl

pair of shared electrons in red,each chlorine atom has 8 e


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Single: One pair of electrons are shared.

Double: Two pairs of electrons are shared.

Triple: Three pairs of electrons are shared

or


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1. Write the valence electrons of the Nitrogenatom

2. Write the total number of electrons fromboth atoms

3. Draw the dot diagram

4. Arrange the electrons using octet rule (bothatoms must have 8 electrons how many

electrons must they share?)


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N from family VA= 5 electrons

For the molecule N2 are 10 electrons

Sharing just one pair doesnt apply the octet rule.

Neither sharing two pairs of electrons apply

But sharing THREE pair of electrons the octet rule

does apply or N N

N

N

N

N

N

N

N

N


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F2 NH3 H2

H2S HBr

CH4 CO2 CO O2 CCl4


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Polar covalent: between atoms of different elements.

Example H2O, H2S, CO2, CCl4. The type of bond isalso determined by the difference of theelectronegativity values of the elements


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Compound Electronegativityvalue of each atom Electronegativitydifference Type of bondF2 F: 4.0 F: 4.0 4.0 4.0 = 0 Covalent Non-polarH2S

NaF

RbBr

NH3

HF

MgO

KCl

N2

CH4


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In chemistry, polarity refers to a separation ofelectric charge leading to a molecule havingan electric dipole.

Polar: Is a molecule that can dissolve in waterlike Salts (NaCl, KF, etc) and Acids (HCl,HNO3, etc).

Non polar: Is a molecule that can not dissolvein water like fats, oils, gasoline, methane gas(CH4) carbon tetrachloride (CCl4), CO2.
http://en.wikipedia.org/wiki/Chemistryhttp://en.wikipedia.org/wiki/Electric_chargehttp://en.wikipedia.org/wiki/Dipolehttp://en.wikipedia.org/wiki/Dipolehttp://en.wikipedia.org/wiki/Electric_chargehttp://en.wikipedia.org/wiki/Chemistry


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A water molecule, a commonly-used example

of polarity. The two charges are present with anegative charge in the middle (red shade), and apositive charge at the ends (blue shade).
http://en.wikipedia.org/wiki/Water_moleculehttp://en.wikipedia.org/wiki/Water_molecule


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Metallic bonding is the electromagneticinteraction between delocalized electrons, called"electrons sea.

The electrons sea are the responsible for thephysical properties of solid metals: conduct heat

and electricity, generally high melting and boilingpoints,strong, malleable (can be hammered orpressed out of shape without breaking), ductile(able to be drawn into a wire), metallic lustre

The elements involved in this type of bonding aremainly the transition metals like Fe, Cu, Au, Ag,Al, Zn, Pt, etc.
http://en.wikipedia.org/wiki/Delocalized_electronhttp://en.wikipedia.org/wiki/Delocalized_electron


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Are the forces holding molecules together Dipole-dipole forces Weak London dispersion or van der Waal's force. Hydrogen bond

Certain substances such as H2O, HF, NH3 formhydrogen bonds, and the formation of which affectsproperties (solubility) of substance. Other compoundscontaining OH and NH2 groups also form hydrogen

bonds. Molecules of many organic compounds such asalcohols, acids, amines, and aminoacids contain thesegroups, and thus hydrogen bonding plays a importantrole in biological science.
http://www.johnco.cc.ks.us/~pdecell/chemistry/hydrobnds.htmlhttp://www.johnco.cc.ks.us/~pdecell/chemistry/hydrobnds.html


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Which of thefollowing pairshas thestrongest

hydrogen bond.

a) HCl or HFb) NH3 or PH3

c) H2O or H2S

chemical bonding - important concepts in inorganic chemistry

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