mr. ed’s chemistry 9701
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Mr. Ed’s Chemistry 9701. Term 1 Week 2. Chemical Reactivity. How reactive an element is depends on the electron configuration of its atoms. The electrons in the outer energy level are known as valence electrons Noble Gas configuration. The magic number 8: octet rule. - PowerPoint PPT PresentationTRANSCRIPT
Mr. Ed’s Chemistry9701
Term 1Week 2
Chemical Reactivity
How reactive an element is depends on the electron configuration of its atoms.
The electrons in the outer energy level are known as valence electrons
Noble Gas configuration. The magic number 8: octet rule.
Cations! . . . Again.
Group 1, 2, and 3: Easy to loose 1, 2, or 3 electrons. Become positively charged! Group 1 always 1+ charge Group 2 always 2+ Group 3 . . . + ++
Anions . . .
Group 5, 6, and 7: Nitrogen family – Pnictogens. Oxygen family – Chalcogens. Halogens Require 3, 2, or 1 electron for Nobel Gas Negative charged
Attraction
Positive and negative charges attract each other!
Think magnets!
Naming . . . NomenclatureGreek number prefixes.
1. Mono-
2. Di-
3. Tri-
4. Tetra-
5. Penta-
6. Hexa-
7. Hepta-
8. Octa-
9. Nona-
10.Deca-
Binary ionic compounds.
Made of just two elements Is the compound ionic or molecular?Compounds of metals with non-metals Ionic
Binary ionic compounds.
The cation named firstJust the metal’s nameTransition metal must always be
followed by a Roman numeralFollowed by the name of the anion.Mono- is never used for the first part.
Binary ionic compounds.
If there is only one type of compoundGreek numbering is NOT usedCalcium bromide – CaBr2
There is only one bromide of calciumNOT calcium dibromide!
Binary ionic compounds.
For naming anionsElement name and end in –ide
Chlorine Chloride
Bromine Bromide
Oxygen Oxide
Sulfur Sulfide
Nitrogen Nitride
Phosphorus Phosphide
Binary ionic compounds.
Name Sodium chloride Copper(II) chloride Zinc sulfide Magnesium nitride Potassium oxide Aluminum sulfide
Formula
NaCl
CuCl2
ZnS
Mg3N2
K2O
Al2S3
Polyatomic ions.
A group of more than one atom as ion Anions often end in –ate or –ite.
Cations . . . Few Ammonia: NH3 – Ammonium NH4
+
Water: H2O – Hydronium H3O+ Many cations end in -nium
Polyatomic Ionic compounds.
Cation: Again just the metal’s name.Ammonia: NH3 – Ammonium NH4
+
For transition metals: Again Roman numerals for oxidation state.
Second part of: Anion
Ployatomic ionic compounds.
If there is only one type of compoundGreek numbering is NOT usedCalcium carbonate – Ca(NO3)2
There is only one nitrate of calciumNOT calcium dinitrate!
Some common polyatomic cations.
You should know these! End in –ate. OH– – hydroxide NO3
– – nitrate
SO42– – sulfate
CO32– – carbonate
HCO3– – hydrogencarbonate (bicarbonate)
PO43– – phosphate
ClO3– – chlorate
Some more polyanions.
You might see these. NO2
– – Nitrite ion
SO32– – Sulfite ion
PO33– – Phosphite ion
ClO2– – Chlorite
End in -ite
Why do ions form?
The driving force is . . .
ENERGY!
Why do ions form?
Electronegativity A measure of the ability of an atom to attract
electrons (or electron density) towards itself. Proposed by Linus Pauling in 1932. Two: Chemistry and Peace
Why do ions form?
The scale 0.70 to 4.00 0.79 for Cesium . . . The least 3.98 for Fluorine . . . The most Size of atom Charge of nucleus
Viva la difference!
Differences in electronegativity (E.N.) Two atoms of the same element: E.N. = 0 Electron are equally shared
Viva la difference!
Differences in electronegativity (E.N.) Two atoms of the same element: E.N. = 0 Electron are equally shared
Viva la difference!
When both nuclei have same chargeBoth also have same number of e– And same e– configurationAll forces are balancedNon-polar covalent bond
Viva la difference!
Differences in electronegativity (E.N.)Two atoms are of different elements:E.N. difference ≠ 0Electron are not equally sharedMost E.N. atom gets more of the e–
Viva la difference!
Differences in electronegativity (E.N.) E.N. 0.5 Non-polar covalent E.N. 0.5 2.1 Polar covalent E.N. above 2.1 Ionic
Some examples
Hydrogen – 2.20 Alkali metals – least electronegative
Li – 0.98 Rb – 0.82
Na – 0.93 Cs. – 0.79
K – 0.82 Fr – 0.70
Some examples
Hydrogen – 2.20 Alkali metals – least electronegative
Li – 0.98 Rb – 0.82
Na – 0.93 Cs. – 0.79
K – 0.82 Fr – 0.70
Francium:At any given time, as little as 30 g exists throughout the
Earth’s entire crust.
Some examples
Halogens – most electronegative
F – 3.98 I – 2.66
Cl – 3.16 At – 2.2
Br – 2.96
Astatine:Rarest naturally occurring element, less than 25 g
exists at any one time in the Earth’s entire crust.
Some examples
Top six most electronegative
1. F – 3.98 4. N – 3.04
2. O – 3.44 5. Kr* – 3.00
3. Cl – 3.16 6. Br – 2.96
Calculations
Easy – Just subtract E.N. valuesNaClCl = 3.16 and Na = 0.933.16 – 0.93 = 2.23Definitely ionic
Calculations
MgOO = 3.44 and Mg = 1.313.44 – 1.31 = 2.13Also definitely ionic
Calculations
NH3
N = 3.04 and H = 2.203.04 – 2.20 = 0.84Polar covalentH→N←H
↑
H
Calculations
H2OO = 3.44 and H = 2.203.44 – 2.20 = 1.24Strongly polar covalent
Calculations
CH4
C = 2.55 and H = 2.20 2.55 – 2.20 = 0.35 Non-polar covalent
Fortunately . . .
For ionic compounds: No need to calculate.
Simple rules.Compounds of metals: ionicMetal – Non-metalGroups I, II, most of III, Transitions,
bottoms of IV, and V
Fortunately . . .
Compounds of non-metals: Ionic or covalent
Non-metal – Non-metalB, top of groups IV, and V, most of VI,
and group VII.Metal to metal?Alloys
Metal – Metal compounds are rare.
Unfortunately . . .
Naming covalent compoundsLike ionic compounds usually has two
partsFirst part is the LEAST electronegative
elementJust the element’s name
Need no know at least first five most E. N.
Covalent compounds . . .
Naming covalent compoundsLike ionic compounds usually has two
partsFirst part is the LEAST electronegative
elementJust the element’s name
Need no know at least first five most E. N.
Ionic Bonds
Loss of electrons by one atom, gain of electrons by another
Oxidation Is LossReduction Is GainVery strong bonds ElectrostaticCan involve more than one electronMagnetic
OIL RIG
Ionic Solid Structure
Simple repeating structure Ions alternateLatticeGiant structureNo one atom or ion bound to any other
specific atom or ion
Ionic Properties
High melting temperatureHigh boiling temperatureUsually Soluble in polar solventsElectrically conductive when melted or
dissolvedCrystalline – easily cleaved
When do they form?
Great difference between the electro-negativities of elements involved
When little difference . . .
Electro-negativity: A measure of an atom’s tendency to gain
electrons
Related to:Electro-Chemical Series
The more electronegative elements:Upper Right
→The least electronegative:
Lower Left→