Ionic Compounds and Metals

Chapter 7

7.1 – Ion Formation What is a chemical bond?

o The force that holds two atoms together.

Bond formationo attraction between the positive nucleus of one atom and

the negative electrons of another atomo attraction between positive and negative ions

Ions Atoms or groups of atoms with a positive or

negative charge

Cationo Positively charged iono Forms when an atom loses one or more valence

electrons

Metal ionso Metals atoms are reactive because they lose valence

electrons easily.• Examples: Magnesium to Mg2+, Potassium to K1+

Ions Anion

o Negatively charged iono Forms when an atom gains one or more electronso Anions designated by the ending –ide

Nonmetal ionso Gain the number of electrons that, when added to their

valence electrons, equals 8• Examples: Phosphorus to Phosphide (P3-) , Fluorine to

Fluoride (F1-), Oxygen to Oxide (O2-)

7.2 – Ionic Bonds and Ionic Compounds

Ionic bondo Bond formed by electrostatic force holding oppositely

charged particles together

Ionic Compoundso Compounds that contain ionic bonds

Binary Ionic Compoundso Contain a metallic cation and a nonmetallic anion

• Examples: sodium chloride (NaCl), magnesium oxide (MgO)o Overall charge of Compound must equal zero

Ionic Compounds Examples

o Sodium and Nitrogen

o Lithium and Oxygen

o Strontium and Fluorine

o Aluminum and Sulfur

Properties of Ionic Compounds

Physical Structureo Cations and Anions exist together in a ratio determined

by the # of electrons transferred Crystal lattice

o 3-dimensional geometric arrangement of particleso Each cation is surrounded by anions and each anion is

surrounded by cations Physical Properties

o Dependent upon how strongly the particles that make up the matter are attracted to one another• Melting point, boiling point, hardness, conductivity

7.3 – Names and Formulas for Ionic Compounds

Formula unit – the chemical formula for an ionic compound which represents the simplest ratio of the ions involved.

Monatomic ions = one atom ionso Examples: Li1+, Mg2+, N3-, Te2-, F1-

o The superscripted number next to an ion is referred to as the oxidation number.

Binary Ionic Compounds

Bond between a cation and an anion.o Cation written first followed by aniono The ratio of ions must balance the oxidation numbers

(no overall charge)o Examples: K1+ and O2- create K2O

• Na1+ and Cl1-

• Cs1+ and N3-

• Al3+ and Br1-

Polyatomic Ions Ions made up of more than one atom.

o Pg. 221 Table 9o Bond in the same manner as binary ionic compounds

Exampleso Na1+ and NO3

1-

o Ca2+ and ClO31-

o Al3+ and CO32-

Naming Ionic Compounds

Oxyanions – polyatomic ion composed of an element, usually a nonmetal, bonded to one or more oxygen atoms.

Chemical nomenclature1. Name the cation followed by the anion. (cation is always written first)2. For monatomic cations, use the element name.3. For monatomic anions, use the root of the element name plus the suffix –ide.

Example: CsBr

4. To distinguish between multiple oxidation numbers of the same element, the name of the chemical formula must indicate the oxidation number of the cation. The oxidation number is written as a Roman numeral in parentheses after the name of the cation.

Example: Fe2+ and O2- ions form FeO, iron(II)oxideFe3+ and O2- ions form Fe2O3, iron(III)oxide

5. When the compound contains a polyatomic ion, simply name the cation followed by the name of the polyatomic ion.

Example: NaOH(NH4)2S

CaCl2

7.4 Metallic Bonds and the Properties of Metals

Metallic Bonds are formed by the attraction of a metallic cation for delocalized electrons.

o Electron sea model – proposes that all the metal atoms in a metallic solid contribute their valence electrons to form a “sea” of electrons.

o Delocalized electrons – electrons present in the outer energy levels of metallic bonds are not held by any specific atom and can move easily from one atom to the next.

Properties of Metals Melting and boiling points

o In general, metals have moderately high melting points and high boiling points.

Malleability, ductility, and durabilityo Metals are malleable (hammered into sheets)o Metals are ductile (drawn into wire)o Metals are durable (strong attractions between cations

and electrons) Thermal conductivity and electrical conductivity

o The movement of mobile electrons around positive metallic cations make metals good conductors.

Hardness and strengtho D block electrons increase the hardness and strength

Metal Alloys Alloy – a mixture of elements that has metallic

properties.o Due to the unique blend of properties, alloy have a wide

range of commercial applications.• List of common commercial alloys pg. 228 Table 13

Substitutional Alloyo Some of the atoms in the original metallic solid are

replaced by other metals of similar atomic size.• Sterling silver

Interstitial Alloyo Formed when the small holes (interstices) in a metallic

crystal are filled with smaller atoms.• Carbon steel