Chapter 6 Ionic & Molecular Compounds.notebook...Chapter 6 Ionic & Molecular Compounds.notebook 2...

Chapter 6 Ionic & Molecular Compounds.notebook

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January 05, 2015

Feb 39:56 AM

Chapter 6: Ionic and Molecular Compounds1. Recall that the group number indicates the number of valence electrons for any element in that group. Each noble gas has eight valence electrons (except helium, which has two).

2. An electron arrangement of eight valence electrons is unusually stable.

3. The octet rule: Most atoms react to achieve a total of eight valence electrons in their valence shell.

4. Atoms gain or lose electrons to achieve a valence octet.

5. If an atom gains or loses electrons to form a valence octet, the new particle would have an unequal number of protons and electrons and would have a net charge.

6. An ion is an atom that has gained or lost electrons and has a charge.

Feb 311:28 AM

Group 7A elements, like chlorine, have seven valence electrons, gain an electron to have an octet, and form an ion with a 1 charge (ions have 17 protons and 18 electrons).

An anion is any atom that contains a net negative charge given that it has an unequal number of protons and electrons.

NOTE: When chlorine forms an ion it has the same number of valence electrons and total electrons as argon.


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January 05, 2015

Feb 311:28 AM

Group 1A elements, like sodium, have one valence electron. In order to have an octet, the elements in this group must lose one electron to form ions with a 1+ charge (ions have 11 protons and 10 electrons).

NOTE: When sodium forms an ion it has the same number of valence electrons and total electrons as argon.

A cation is any atom that contains a net positive charge, given that it has an unequal number of protons and electrons.

Feb 311:29 AM

Trends in Ion Formation1. How do we determine which atoms will gain electrons to form anions and which atoms will lose electrons to form cations?2. Metals lose electrons to form cations and nonmetals gain electrons to form anions.3. The main group metals in Groups 1A, 2A, and 3A form cations. Main group nonmetals in Groups 5A, 6A, and 7A form anions.

The main group metals form cations with charges of 1+ to 3+, whereas the main group nonmetals form anions with charges of 1 to 3.


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January 05, 2015

Feb 311:29 AM

Electron Configuration of Cl atom:

Electron Configuration of Cl ion

Electron Configuration of Na atom:

Electron Configuration of Na+ ion

Feb 311:29 AM

Ionic CompoundsIonic compounds • consist of positive and negative ions.• have attractive forces between the positive and negative ions called ionic bonds.• have high melting and boiling points.• are solid at room temperature.

Salt Is an Ionic CompoundSodium chloride, or “table salt,” is an example of an ionic compound.

Formulas of Ionic CompoundsThe chemical formula of an ionic compoundrepresents the element symbols and subscripts, whichrepresent the lowest wholenumber ratio of ions. In the formula of an ionic compound,• the sum of positively and negatively charged ions is always zero.• the charges are balanced.


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January 05, 2015

Feb 311:48 AM

Charge Balance for NaCl, “Salt”In NaCl,• a Na atom loses its

valence electron. • a Cl atom gains an

electron.• the symbol of the metal

(sodium) is written first, followed by the symbol of the nonmetal (chlorine).

Charge Balance In MgCl2In MgCl2,• a Mg atom loses two valence electrons.• two Cl atoms gain one electron each.• subscripts indicate the number of ions

needed to give charge balance.• the symbol of the metal (magnesium) is

written first, followed by the symbol of the nonmetal (chlorine).

Feb 312:26 PM

Crisscross method: quick way to determine formula for ionic compoundWhen using the crisscross method, remember:

• Transfer the NUMBER but NOT the sign of the charge from one element to the other

• Reduce to the lowest whole number ratioPractice with this website!

1. Determine the oxidation # Al +3 Cl ‐1

2. Make sure the compound is NEUTRAL‐ no charge because same # electrons will be donated & accepted.

3. Use the crisscross method Al +3 Cl ‐1

4. Reduce to lowest whole number ratio

Na1+Cl1‐ Na1Cl1 NaCl sodium chloride

Ca2+F1‐ CaF2 CaF2 calcium fluoride

Li1+O2‐ Li2O1 Li2O lithium oxide

More Examples:

Type I: Naming Binary Ionic Compounds

http://group.chem.iastate.edu/Greenbowe/sections/projectfolder/flashfiles/reaction/bonding1.html


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January 05, 2015

Feb 312:26 PM

Here are two examples where you must reduce

Magnesium oxide Lithium sulfide

Potassium phosphide Aluminum oxide

Practice

Feb 312:26 PM

MgCl2 magnesium chloride K2O potassium oxide

Al2O3 aluminum oxide InF3 indium fluoride

Rb3N rubidium nitride Cs4C cesium carbide

What is the rule for naming binary ionic compounds?

Select the correct formula for each of the following ionic compounds. 1. Na+ and S2– A. NaS B. Na2S C. NaS22. Al3+ and Cl– A. AlCl3 B. AlCl C. Al3Cl3. Mg2+ and N3– A. MgN B. Mg2N3 C. Mg3N2


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January 05, 2015

Feb 312:26 PM

Type II: Naming Binary Ionic Compounds containing metals with more than one charge

2. The metal always goes first. The name of the compound is [name of metal] + [(roman numeral)] + [nonmetal root] + [ide].

1. Transition metals form more than one ion. For example, iron will form the Fe2+ and Fe3+ cation. Copper will form the Cu+ and Cu2+ cation. Roman numerals are used to indicate the charge.

Feb 31:52 PM

Iron(II) oxide Iron(III) oxide

Gold(I) sulfide Gold(III) sulfide

Practice with transition metals

SnS SnS2

CuO Cu2O


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January 05, 2015

Feb 31:52 PM

Polyatomic ions are a special group of ions formed when two or more nonmetal elements interact with one another. The ions formed have a single charge.

Feb 31:52 PM

Na 1+ PO43‐ Na3(PO4)

K1+ SO42‐ K2SO4Mg2+ CO32‐ after reducing Mg(CO3)

Al3+ NO31‐ Al(NO3) 3NH41+ CO32‐ (NH4)2CO3

Criss cross rule applies—use parenthesis when using polyatomic ions

Na3PO4 sodium phosphate

NH4Cl ammonium chloride

K2 SO4 potassium sulfate

Mg CO3 magnesium carbonate

Al(NO3) 3 aluminum nitrate

Naming compounds with polyatomic ions:


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January 05, 2015

Feb 31:52 PM

Type III: Molecular Compounds (NMNM)1. A molecular formula identifies all the components in a molecule of a covalent compound.

2. Table sugar, sucrose (molecular formula C12H22O11) has 12 carbon atoms, 22 hydrogen atoms, and 11 oxygen atoms.

3. Molecular formula only tells us the number of atoms in a molecule not how they are joined or what the structure is.

Feb 47:16 AM

1. name the first element2. use the stem of the second element; add 'ide"3. precede each name with a Greek number prefix to indicate the number of each kind of atom. ( if the first element has only atom no prefix is needed)

Naming Molecular Compounds

http://www.chem.purdue.edu/gchelp/nomenclature/covalent.htm


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January 05, 2015

Feb 47:16 AM

Name the following compounds.

PH3 H2O

SO N2O3

Write the formula for following compounds.

1. sulfur dioxide 2. dihydrogen monoxide

3. phosphorus pentafluoride 4. carbon tetrachloride

Feb 47:09 AM

ElectronDot Formulas of Molecular CompoundsBonding pairs the shared electrons

Lone pairs the none bonding pairs of electrons


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January 05, 2015

Feb 47:16 AM

State the number of valence electrons, bonding pairs and lone pairs in each of the following electrondot formulas

Feb 47:40 AM

Naming HydrocarbonsAlkanesHydrocarbons having single bond functional groups are classified as alkanes where the carbon atoms of the molecule are arranged in chains.

• These formulas all fit the CnH2n+2 rule. • This is also the highest possible H/C ratio for a stable hydrocarbon. • Since the H/C ratio in these compounds is at a maximum, we call them saturated (with hydrogen).

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