metals with variable charge - mr. jeremy t....

© 2013 Pearson Education, Inc. Chapter 5, Section 1 1

Metals with Variable Charge

Most transition metals (3-12) and Group 4A (14) metals form 2 or more positive ions, except Zn2+, Ag+, and Cd2+, which form only one ion.

Metals with Variable Charge

The names of transition metals with two or more

positive ions (cations) use a Roman numeral after the

name of the metal to identify the ion charge.

Naming Ionic Compounds with Variable Charge Metals

Naming FeCl2

Step 1 Determine the charge of the cation from the anion. Analyze the Problem.

Naming FeCl2

Step 2 Name the cation by its element name and use a Roman numeral in parentheses for the charge.

Fe2+ = iron(II) Step 3 Name the anion by using the first syllable of its element name followed by ide . Cl− = chloride Step 4 Write the name for the cation first and the name for the anion second.

iron(II) chloride


Examples of Names of Compounds with Variable Charge Metals

Writing Formulas for Ionic Compounds

Writing the Formula for Iron(III) Oxide

Metal Nonmetal

Ion Iron(III) oxide

Group Transition 6A (16)

Symbol Fe3+ O2–

Learning Check

Write the correct name for CuO.

Write the correct formula for copper(I) nitride.

A polyatomic ion

is a group of atoms.

has an overall ionic charge.

Examples:

NH4+ ammonium OH− hydroxide

SO42−

sulfate CO32− carbonate

PO43− phosphate

Polyatomic Ions


Names and Formulas of Common Polyatomic Ions

Compounds Containing Polyatomic Ions

Polyatomic ions

must be associated with an ion of opposite charge.

form ionic bonds with ions of opposite charge to achieve charge balance.

Example:

Ca2+ NO3−

calcium nitrate ion

charge balance:

Ca(NO3)2

calcium nitrate

Step 1 Identify the cation and polyatomic ion (anion).

Cation: K+ Anion: SO42−

Step 2 Name the cation, using a Roman numeral if needed.

K+ = potassium ion

Step 3 Name the polyatomic ion.

SO42− = sulfate ion

Step 4 Write the name or the compound, cation first and the polyatomic ion second.

K2SO4 = potassium sulfate

Name K2SO4

Learning Check

Name each of the following compounds.

1. Cu(ClO3)2

2. PbCO3

3. Ba3(PO3)2

Solution

Step 1 Identify the cation and polyatomic ion (anion). cation polyatomic ion 1. Cu(ClO3)2 Cu2+ ClO3

−

2. PbCO3 Pb2+ CO32−

3. Ba3(PO3)2 Ba2+ PO33−

Step 2 Name the cation using a Roman numeral, if necessary. cation name 1. Cu(ClO3)2 copper(II)

2. PbCO3 lead(II) 3. Ba3(PO3)2 barium

Solution

Step 3 Name the polyatomic ion. polyatomic ion 1. Cu(ClO3)2 chlorate

2. PbCO3 carbonate 3. Ba3(PO4)2 phosphate

Step 4 Write the name or the compound, cation first

and the polyatomic ion second. compound name 1. Cu(ClO3)2 copper(II) chlorate

2. PbCO3 lead(II) carbonate 3. Ba3(PO3)2 barium phosphite

Write the Formula for Aluminium Hydroxide

Step 1 Identify the cation and polyatomic ion (anion). Al3+ and OH−

Step 2 Balance the charges. Step 3 Write the formula, cation first, using the subscripts from charge balance. Al(OH)3

Break Time!!

Covalence - Formation of H2

In the simplest covalent molecule, H2 , the H atoms

increase attraction as they move closer.

share electrons to achieve a stable configuration.

form a covalent bond.


Electron-Dot Formulas of Covalent Molecules

In a fluorine (F2) molecule, the F atoms

share one of their valence electrons.

acquire an octet.

form a covalent bond.


Elements That Exist as Diatomic Molecules

These seven elements share electrons to form diatomic, covalent molecules.


Electron-Dot Formulas for Some Covalent Compounds


Guide to Drawing Electron-Dot Formulas

Step 1 Determine the arrangement of atoms. In NH3, N is the central atom and is bonded to three H atoms. Step 2 Determine the total number of valence electrons. Total valence electrons for NH3 = 8 e−

Draw the Electron-Dot Formula for NH3

H N H

H

Step 3 Attach each bonded atom to the central atom with a pair of electrons.


H N H

H

Step 4 Place the remaining electrons using single or multiple bonds to complete the octets. 8 valence e− − 6 bonding e− = 2 e− remaining Use the remaining 2 e− to complete the octet around the N atom.


H N H

H

H N H

H

or


Learning Check

Draw the electron-dot formula for CCl4.

Step 1 Determine the arrangement of atoms. In CCl4, C is the central atom and is bonded to four Cl atoms.

Solution

Cl Cl C Cl

Cl

Step 2 Determine the total number of valence electrons. Total valence electrons for

Solution

Step 3 Attach each bonded atom to the central atom with a pair of electrons.

Solution

Cl Cl C Cl

Cl

Step 4 Place the remaining electrons, using single or multiple bonds to complete the octets.

32 valence e− − 8 bonding e− = 24 e− remaining Use the remaining 24 e− to complete the octets around the Cl atoms.

Solution

Cl Cl C Cl

Cl

or

Cl Cl C Cl

Cl

Single and Multiple Bonds

In many covalent compounds, atoms share two or three pairs of electrons to complete their octets.

In a single bond, one pair of electrons is shared.

In a double bond, two pairs of electrons are shared.

In a triple bond, three pairs of electrons are shared.

Step 1 Determine the arrangement of atoms. In CS2, C is the central atom and is bonded to two S atoms.

Draw the Electron-Dot Formula for CS2

S C S

Step 2 Determine the total number of valence electrons. Total valence electrons for


Step 3 Attach each bonded atom to the central atom with a pair of electrons. A pair of bonding electrons (single bond) is placed between each S atom and the central C atom.


S C S

Step 4 Place the remaining electrons using single or multiple bonds to complete the octets.

16 valence e− - 4 bonding e− = 12 e− remaining

The remaining 12 electrons are placed as six lone pairs of electrons on both S atoms. However, this does not complete the octet for the C atom.


S C S

Step 4 Continued: Double and Triple Covalent Bonds: To complete the octet for the C atom, it

needs to share an additional lone pair from each of the S atoms, forming a double bond with each S atom.


S C S

or

S C S

S C S


A Nitrogen Molecule has a Triple Bond

In a nitrogen molecule, N2,

each N atom shares 3 electrons,

each N atom attains an octet, and

the sharing of 3 sets of electrons is called a triple bond.

metals with variable charge - mr. jeremy t....

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