Formula Writing - Mrs. Canale's Science Site · PDF file · 2015-06-042015-06-04 · Formula Writing oxidation number-number assigned to keep track of electron gain or loss lose electron

Formula Writing oxidation number-number assigned to keep track of electron gain or loss

lose electron

cation + gain electron

anion -

cation is written first anion is second

positive ion first negative ion second

METALS (nonmetals)

Binary Compound Polyatomic Compounds

Compound made of only two elements

Compound made of 3 or more elements

Definition (Usually metal with nonmetal) (Usually table E, polyatomic ions)

Use Criss-Cross Use Criss-Cross

Forming Cations

Metals lose electrons to be stable.

Metal ions are positively charged because they

have more positive protons than negative

electrons.

K K+ + e-

potassium potassium ion

Naming Cations Cations are named the same as their parent atoms,

as shown here:

6-3

Forming Anions

Nonmetals gain electrons to be stable.

Nonmetal ions are negatively charged because

they have fewer positive protons than negative

electrons.

6-4

Cl + e- Cl-

chlorine chloride ion

Naming Anions Monatomic anions use the stem of the element’s

name and the ending changed to ide.

6-5

Ion Charges Metals on the left side of the periodic table form only

one ion. Metals in group 1 and 2 their charge is their

group number.

Many metals form more than one ion. Often these

are the transition metals.

The charge of a nonmetal is = to its group number – 8.

Copyright 2011 John Wiley & Sons, Inc

6-6

Your Turn!

Calcium is an element in group 2A. Which of

the following statements is correct about

calcium forming an ion?

a. Ca gains two electrons, forming Ca2+

b. Ca gains two electrons, forming Ca2-

c. Ca loses two electrons, forming Ca2-

d. Ca loses two electrons, forming Ca2+

6-7

Your Turn!

Phosphorus is a nonmetal in group 5A. The charge

on the phosphide ion is

a. -3 because the element lost 3 electrons.

b. -3 because the element gained 3 electrons.

c. +3 because the element lost 3 electrons.

d. +3 because the element gained 3 electrons.

6-8

Binary Compound Polyatomic Compounds

Second element name ends in “-ide”

Second element can end in -”ate” -”ite” -”ium” ONLY -”ide’s”: “peroxide, hydroxide, cyanide

Definition

Aluminum Sulfide Aluminum Sulfate 1. Look up symbol for the element on

Table S

Al S

2. Write the oxidation number, (which

are found on the Periodic Table, above

each symbols as a superscript):

Al +3 S-2

3. Crisscross the oxidation numbers and

omit the charge signs. Write the numbers

below the symbols as subscripts.

Al2S3

Note: The crisscrossing of the oxidation

numbers conserves the charge.

The sum of the oxidation numbers of all

of the atoms in a compound is always

zero.

4. When each element has the same

oxidation number, these numbers are

dropped and the formula is correct as

written in step 1.

1. Look up symbol for the element on Table S;

polyatomic ion on Table E

Al SO4

2. Write the oxidation numbers, which are

found on the Periodic Table, above each

symbols as a superscript:

Al +3 SO4-2

3.Place the polyatomic ion in parentheses

Crisscross the oxidation numbers and omit

the charge signs. Write the numbers below the

symbols as subscripts.

Al2(SO4)3

The sum of the oxidation numbers of all of the

atoms in a compound is always zero.

4. When each element has the same oxidation

number, these numbers are dropped and the

formula is correct as written in step 1.

Sodium Sulfide

Na +1 S 2-

Na +1 S 2-

Na2S

Sodium Sulfate -ide on PT

-ate on Table E

Na +1 SO4

2-

***MUST use parentheses here- if it’s more than one!***

Na2 SO4

Writing Formulas for Ionic

Compounds

Write the formulas for the compounds containing the

following ions:

1. Al3+ and F-

2. Ca2+ and N3-

3. K+ and Cl-

4. Mg2+ and I-

6-11

AlF3 Ca3N2

MgI2

KCl

Your Turn!

What is the correct formula for

the compound beryllium (Be)

fluoride (F)?

a. BeF

b. Be2F

c. BeF2

d. Be2F2

6-12

Your Turn!

What is the correct formula for the

compound silver (Ag) sulfide (S)?

a. AgS

b. AgS2

c. Ag2S

d. 2AgS

6-13

Naming Compounds Ionic compounds

Naming Binary Compounds 1. The element with the positive ionic charge is written first. 2. The second word is formed by changing the ending of the name of the element to “ide”. Example bromine becomes bromide. Metals usually have positive ionic charges Nonmetals (when combined with metals) have negative charges. NaCl sodium chlorine sodium chloride

Polyatomic Ions

Look up the name of the polyatomic ion on chart table E When polyatomic ion is second 1. write the name of the first element 2. write the name of the polyatomic ion Na2SO4 Sodium sulfate If polyatomic ion first 1. look up ion name 2. follow ending for binary compounds NH4Cl ammonium chlorine ammonium chloride

Your Turn!

What is the correct name for

CdF2?

a. Cadmium flourine

b. Cadmium flouride

c. Cadmium fluorine

d. Cadmium fluoride

6-15

Naming & Writing Compounds Elements with more than one positive oxidation number (Transition Metals)

(This is called the Stock System) When the oxidation number varies we us a Roman numeral in parentheses to indicate the charge. Roman number is used for the positive element only!!! (I, II, III, IV, V, VI, VII, VIII, IX, X) FeO Iron (II) oxide Fe2O3 Iron(III) oxide

Alternative method for compounds ALL NON METALS ONLY!!!

We can also use prefix to indicate the number of each element mon 1, di 2, tri 3, tetra 4, penta 5, hexa 6, hepta 7, octa 8, non 9, deca 10

***No criss cross*** If the first element is 1, don’t write mono

Carbon monoxide CO dinitrogen trioxide N2O3

**TRANSITION METALS!!!!!

Naming Binary Ionic Compounds

1. Write the name of the cation.

2. Write the charge on the cation as a Roman

numeral in parenthesis.

3. Write the name of the anion with suffix –ide.

CoCl3

Fe3P2

CuO

SnBr4

6-17

cobalt(III) chloride

iron(II) phosphide

tin(IV) bromide

copper(II) oxide

Naming Binary Ionic Compounds

More Practice

1. CoCl3

2. K2S

3. HgF2

4. AgBr

5. Fe3P2

6. PbI4

6-18

cobalt(III) chloride

potassium sulfide

mercury(II) fluoride

iron(II) phosphide

silver bromide

lead(IV) iodide

Naming Binary Compounds


6-19

Naming Compounds

Containing Polyatomic Ions


6-20

Your Turn!

Sulfate is SO42-. Name the

compound FeSO4.

a. iron sulfate

b. iron(I) sulfate

c. iron(II) sulfate

d. iron(IV) sulfate

6-21

Your Turn!

V2O5 is

a. divanadium pentoxide

b. vanadium pentoxide

c. vanadium(II) oxide

d. vanadium(V) oxide


6-22

Your Turn!

Sulfur dioxide is

a. SO

b. S2O

c. SO2

6-23

Chemical Bonding Chemical bonds are the forces that hold atoms together in a compound. • when atoms bond they release energy and become more stable

Ionic Covalent Metallic

Ionic Bonds

Metal/nonmetal

e- is transferred from the metal to the

nonmetal

EN difference greater than 1.7

Greater the EN

difference, greater the ionic character

Transfer e-

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Your Turn!

Metals generally form ions by

a. Gaining electrons, forming positive ions

b. Losing electrons, forming positive ions

c. Gaining electrons, forming negative ions

d. Losing electrons, forming negative ions


11-26



Ionic Solid

hard crystalline high melting and boiling points do not conduct electricity in the solid state do conduct electricity in the molten (liquid) or aqueous state (aq)-electrolyte (ions) NaCl

Ionic Bond Formation

An ionic bond is the attraction of

oppositely charged particles.

11-28

[ Cl ]- Cl [Na]+ Na +

NaCl Crystal

11-29

Formation of Magnesium

Chloride Mg needs to lose 2 electrons: [Ne]3s2

Cl needs to gain 1 electron: [Ne]3s23p5

We will need to transfer 2 electrons from Mg to Cl.

11-30

2 Cl are needed!

Covalent Bond

2 nonmetals

Nonpolar Polar Coordinate

Same nonmetals

Share the electrons equally

Difference of 0

Moochers one atom donates a pair of electrons to be share, the other contributes none

H20 NH4

+

Share e-

Cl2 CO2

Different nonmetals

Share the electrons unequally

Difference of

0.1-1.7

H3O+







Molecular Substance Network Solid

are brittle in the solid form All 3 states of matter are poor conducts of heat and electricity Low melting and boiling points

Hard crystalline Are poor conductors of heat and electricity High melting boiling points

C6H12O6 CO2

HCl

C-diamond SiO2-quartz/sand SiC

Metallic Bonds

metals

Electrons move freely from one atom to

another.

“sea of mobile electrons”

good conductors of electricity and heat in any state malleable ductile high melting and high boiling points

Metals

Mobile e-

+ + + + + ++ + + + + + +

- - - - - - - -- - - - - - - - - - -

+ + + + + + + + + + + +

Venn diagram

Ionic Covalent

Venn diagram

Ionic Covalent

Are forces acting between atoms to hold them together

Can form when atoms make contact

Either absorb or release energy when formed

Create new species with chemical and physical properties unlike constituent atoms

Form because atoms want to have complete outer shells

Forms when one atom donates electrons to another

Exist between ions

Holds ions together in an ordered 3-d array, called an ionic crystal

Typically exist between atoms on opposite sides of the periodic table

Results from electrostatic attraction between opposite charges

Forms when atoms share 2,4,6 electrons

Builds molecules

Can be polar or non-polar

Exist between neutral atoms

Forms when atoms that tend to gain electrons come into contact with one another

Generally form between atoms in the upper right hand corner of the periodic table

Lewis Dot Structure

Octet Rule

molecules and ions need to have eight electrons in their valance level as the result of bond formation Hydrogen and helium want 2

Rules for drawing an atom. Shows the number of valence electrons for an individual atom Find the number of valence e

Put 2 on top

Put 1 on each side

double up

Lewis Structures of Atoms


11-38

Figure 11.4 Lewis structures of the first 20 elements.

Dots represent electrons in the outermost s and p

energy levels only.

Predicting Formulas of Ionic

Compounds Elements within a group behave similarly

because their valence electron configuration is

the same.

If sodium oxide is Na2O, then oxides of other

Group IA elements will also exist in a 2:1 ratio:

Li2O, K2O, Rb2O

If sodium oxide is Na2O, then sulfides of the

Group IA elements will also exist in a 2:1 ratio.

Na2S, K2S, Rb2S


11-39

Ionic

Metal/nonmetal OR an ION (just choose half)! Write the formula-tell how many of each atom you need Metal: no dots positive charge [ ] Nonmetal: 8 dots negative charge [ ]

Aluminum bromide

Your Turn! How many valence electrons are present in an atom of aluminum in the ground state and what charge will it form when it loses those electrons?

a. 3, +3

b. 3, -3

c. 5, +3

d. 1, +1

e. 13, +3


11-41

Your Turn!

How many valence electrons are present in

an atom of bromine in the ground state and

how many does bromine need to gain to have

the same electron configuration as a noble

gas?

a. 1, 7

b. 2, 6

c. 3, 5

d. 7, 1


11-42

Covalent 2 non metals 1. Determine the total number of valence e. 2. Draw the skeletal structure. (If only one atom, it will be in the center-central atom.) 3. Put 2 e between each atom.

4. Complete the octet rule for all non-central atoms.

5. Put remaining e on the central atom. 6. Check work.

7. If not enough electrons, make double or triple bonds.

***MOLECULE!!!!!!!***

The Covalent Bond Molecules exist as discrete units held together by

covalent bonds.

A covalent bond consists of a pair of electrons

shared by two atoms.

Figure 11.8 The formation of a hydrogen molecule

from two hydrogen atoms. The two 1s orbitals

overlap, forming the H2 molecule.

11-44

Shapes and Polarity of Molecules

Determining Polarity

Symmetrical - non polar - opposite sides match

Asymmetrical - polar - opposite sides don’t match

Cross test + ** MUST be symmetrical in both directions to be considered Non-Polar. “SNAP”

(ALL NON-METALS!!!!)

HBr H Br

CO2 O C O

CH4 (non polar)

NH3

H2O

Shape Definition Example Ball and Stick Model

linear

tetrahedral

pyramidal

bent

2 atoms connected 3 atoms in a line

1 central atom with 4 atoms around it No unpaired e around central atom

1 central atom with 3 atoms around the central

Atom 1 pair of e not shared

1 central atom, with 2 other atoms off the central atom 2 pairs of e not shared

Always polar

Always polar

Check symmetry

Check symmetry

C H

H

H

H

CH3F (polar)

N H H H

O

H H

Molecular Shape

Figure 11.12 Geometric shapes of common molecules. Each molecule is shown as a ball and stick model (showing

the bonds) and as a spacefilling model (showing the

shape).


11-47

Intermolecular Forces

Are the forces that exist between individual molecules--weaker than a bond

Hydrogen Bonding Dipole - Dipole

dipole - polar molecule

H-Br

Atom with the higher EN will be negative.

between polar molecules

Van der Waals

London Dispersion between non polar molecules

Diatomic elements Noble gases Organic-C

Stronger the intermolecular force, higher the melting and boiling point

Ionic > H-bond > Molecular (Covalent molecules)

between molecules

containing

Hydrogen bonded with

F, O, N

small highly

electronegative

H-Br *****H-Br H-F **H-F

Force is stronger: 1. Closer they are 2. Heavier they are

CH4 ****CH4

NaCl (aq)

Molecule- Ion Attraction

Ionic solids when placed in water dissociate ( separate) due to the attraction of opposite charges Polar and ionic (aq)

Na+ Cl -

Your Turn!

What is the molecular geometry for CH2O?

a. linear

b. trigonal planar

c. tetrahedral

d. trigonal pyramidal

e. bent


11-50

: ..

.. H C O

H

Your Turn!

What is the molecular geometry for NF3?

a. linear

b. trigonal planar

c. tetrahedral


e. bent


11-51

F N F

F .. : :

: : .. .. ..

.. ..

Your Turn!

Is the molecule NF3 polar or nonpolar?

a. Polar, because it has polar bonds

arranged symmetrically around the N.

b. Polar, because it has polar bonds

arranged asymmetrically around the N.

c. Nonpolar, because it has polar bonds

arranged symmetrically around the N.


11-52

Your Turn!

What is the molecular geometry for CF4?

a. linear

b. trigonal planar

c. tetrahedral


e. bent


11-53

Your Turn!

What is the molecular geometry for CO2?

a. linear

b. trigonal planar

c. tetrahedral


e. bent


11-54

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Formula Writing - Mrs. Canale's Science Site · PDF file · 2015-06-042015-06-04 · Formula Writing oxidation number-number assigned to keep track of electron gain or loss lose electron