Physical Science 1Chapter 20 – Chemical Bonds

Meet the Elements – They Might be GiantsElemental Funkiness

Combining Elements• The chemical & physical properties of the elements are

different than the properties of the compound they make up

• Na + Cl2 → NaCl

• Reaction of Sodium with Chlorine

→

Chemical Formulas• Chemical shorthand of compounds and

molecules

• Uses the chemical symbols and trailing subscripts to illustrate the type and number of each atom involved in the chemical bond.

• Water = H2O

Hydrogen

2 atoms of the previous element = 2 hydrogen atoms

Oxygen

No subscript is understood to mean 1 atom of the previous element

Practice with Chemical Formulas Common Name Chemical Formula Types & Number Type of Bond

of Elements involved (ionic - covalent)

• Sand SiO2

• Milk of Magnesia Mg(OH)2

• Sucrose C12H22O11

• Vinegar HC2H3O2

• Ethanol C2H5OH

→

Atomic Stability• Why do atoms form compounds?

– To become stable

• What does stable mean to an atom?– Full Set of Valence electrons

• Atoms want to have the electron configuration of a noble gas

• Atoms will gain, lose or share electrons in order to obtain a full set of valence electrons – Chemical Bonds

Types of Bonds• IONIC BONDS

– between metals & nonmetals– Electrons form a give take

relationship• metals give e- (cation) • nonmetal take e- (anion)

– Held together by attraction of opposite charges

IONIC ANIMATION

• Chemical Bonds

Table Polyatomic IonsIon – a charged particle due to gaining or losing e-Cations = positive ions, lost e- METALSAnions = negative ions, gained e- NONMETALSPolyatomic Ions

– The prefix poly- means many in Greek. – ion consisting of a molecule with many covalently bonded atoms – act as a single unit– polyatomic ion is also referred as a radical – Usually end in –ate & –ite – -ide usually indicates binary compounds

+1 CHARGE -1 CHARGE -2 CHARGE -3 CHARGE

ion name ion name ion name ion name

NH4+ ammonium NO2

- nitrite CO32- carbonate PO3

3- phosphite

H3O+ hydronium NO3

- nitrate SO32- sulfite PO4

3- phosphate

Hg22+ mercury(I) OH- hydroxide SO4

2- sulfate

CH3COO-

C2H3O2-

acetate S2O32- thiosulfate

CN- cyanide CrO42- chromate

CNS- thiocyanate Cr2O72- dichromate

MnO4- permanganate

ClO3- chlorate

ClO4- perchlorate

IO2- iodite

IO3- iodate

Name & Formula 2-D Structure 3-D Representation

Ammonium NH4+

Hydroxide OH–

Nitrate NO3–

Nitrite NO2–

Acetate C2H3O2 –

CH3COO

Carbonate CO32-

Sulfate SO42-

Sulfite SO32-

Phosphate PO43-

+ 1 cation

– 2 anions

– 1 anions

– 3 anion

• COVALENT BONDS– Between 2 nonmetals– Electrons are shared between both elements– Polar Bonds

• an unequal sharing of the e-

• Due to a difference of electro-negativity of the atoms

– F is the most electronegative element on PT– A simulation of polar covalent bonding in

the H2O molecule Only valence electrons are shown

– Non-polar Bonds • an equal sharing of e-

• nonpolar bond animation

– Multiple Bonds – More than one pair of electrons can be shared between atoms

• Double Bonds = 2 shared pairs of e-

• Triple Bonds= 3 shared pairs of e-

Chemical Bonding• COVALENT QUIZ

Comparing ionic and molecular compounds

Molecular compounds Ionic compounds

Smallest particles molecules cations and anions

Origin of bonding electron sharing electron transfer

Forces between particlesstrong bonds between

atomsweak attractions between

molecules

Strong attractions between anions and cations. strong

repulsions between ions of like charge

Elements present close on the periodic table widely separated on the periodic table

Metallic elements present rarely usually

electrical conductivity poor good, when melted or dissolved

state at room temperature solid, liquid, or gas solid

melting and boiling points lower higher

other names covalent compounds salts

• Name this compound Ba(Na)2

• BANANA

• http://www.accessexcellence.org/RC/VL/GG/ecb/covalent_ionic_bonds.html

• http://misterguch.brinkster.net/ioniccovalentworksheets.html

• http://www.visionlearning.com/library/module_viewer.php?mid=55

Group the compounds by ratios 1:1, 1:2, 2:1 1:3 & 2:3Using a PT record the group for each element in all compounds Record each group

Based on your patterns, Write rules for the ratio of elements in a compound LiBr

Al2O3

BeS

Na2O

CaBr2

K2Se

AlF3

MgCl2

B2S3

MgTe

NaF

KCl

CaI2

NaAt

BI31. Using your rules, predict a formula between Li & F and between Li & O

2. Using your rules, choose elements to make four compounds that are not already on the sheet.

3. Explain why MgCl2 is correct and Cl2Mg is incorrect.

4. How is MgCl2 possible and MgLi2 is not?