physical science 1 chapter 20 – chemical bonds meet the elements – they might be giants...
TRANSCRIPT
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?