1. IV. Chemical Bonding

2. Dots represent valence electrons
Dots represent valence electrons. Everything else (inner shell electrons and nucleus) is called the Kernel and is represented by the symbol.
Phosphorous has 5 valence electrons so we draw 5 dots around the symbol for phosphorous.
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3. It does not matter which side you start from.
The correct order to fill in the dots is to make a pair from the first 2 electrons then we fill in one on each side before we pair up. 1 2 Ne 5 3 8 6 4 7
It does not matter which side you start from.
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4. The correct order to fill in the dots is to make a pair from the first 2 electrons then we fill in one on each side before we pair up. 5 8 Ne 1 7 4 2 6 3
This will let you know how many electron pairs and how many unpaired electrons are in the atom’s valence shell
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5. Draw the Lewis Dot Structures of the first 18 elements.
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6. What is a chemical bond? When an atom gains, loses or shares electrons to complete their outer shell (octet)
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7. Atoms attain a stable valence electron configuration by bonding with other atoms. Noble gases have stable valence configurations and tend not to bond.
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8. Metals tend to react with nonmetals to form ionic compounds
Metals tend to react with nonmetals to form ionic compounds. Nonmetals tend to react with other nonmetals to form molecular (covalent) compounds. Ionic compounds containing polyatomic ions have both ionic and covalent bonding.
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9. Two major categories of compounds are ionic and molecular (covalent) compounds.
Ionic compounds are formed when a metal combines with a nonmetal.
Ionic compounds have ionic bonds.
Molecular compounds are formed between two or more nonmetals.
Molecular compounds have covalent bonds.
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10. Chemical bonds are formed when valence electrons are :
Ionic: transferred of electrons from a metal to a non metal
Covalent: shared between two or more non metals
Metallic: mobile electrons within a metal
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11. Polyatomic ions are groups of atoms covalently bonded together that have a negative or positive charge.
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12. Polyatomic ions are held together by covalent bonds but form ionic bonds with other ions.+
Ionic bond H -
Covalent bonds
H N H Cl H
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13. The bonds holding metals together in their crystal lattice are called metallic bonds.
All metals have metallic bonds
“Positive ions immersed in a sea of mobile electrons”
Bonds are between Kernels, leaving the valence electrons free to move from atom to atom
Mobile electrons give metals the ability to conduct electricity
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14. Magnesium atom Magnesium ion
When metals lose electrons to form ions, they lose all their valence electrons. The Lewis Dot Structure of a metal ion has no dots. The charge indicates how many electrons were lost.
Magnesium atom Magnesium ion
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15. When nonmetals gain electrons, they fill up their valence shell with a complete octet (except hydrogen.) The ion is placed in brackets with the charge outside the brackets.
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16. When a bond is formed, energy is released
When a bond is formed, energy is released. Energy is needed to break a bond
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17. The desire for eight valence electrons in the outer shell
What is the octet rule?
The desire for eight valence electrons in the outer shell
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18. Regents Question: 06/02 #3 þ Which compound contains ionic bonds? NO
CaO
(4) CO2
Nitrogen – nonmetal
Oxygen – nonmetal
Calcium – metal
Carbon – nonmetal þ
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19. Regents Question: 08/02 #11
Which formula represents an ionic compound?
(1) NaCl
(2) N2O
(3) HCl
(4 )H2O þ
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20. What type of bonding would sodium and chlorine have?
IONIC
How do you know?
Sodium is a metal and chlorine is a non metal
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21. Compounds with Ionic bonds have the following properties.
- Solids with high melting and boiling points (strong attraction between ions)
Crystalline solids that form regular geometric patterns
Hard
Electrolytes: able to conduct electricity
Do not conduct electricity as solids but do when dissolved or molten – ions are charged particles that are free to move
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22. Ionic solids conduct electricity when dissolved or molten
Ionic solids conduct electricity when dissolved or molten Molecular solids do not.
Solution conducts electricity
Solution doesn’t conduct electricity
Ionic Solid dissolved in water
Molecular Solid dissolved in water
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23. Fluorine is assigned the value 4.0 – the highest of any element
Electronegativity values are assigned according to arbitrary scales. (5.2j)
Fluorine is assigned the value 4.0 – the highest of any element
Nonmetals have high electronegativity – they want to attract electrons so they can fill their valence shell
Metals have low electronegativity – they want to lose electrons to get rid of their valence shell
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24. Electronegativity indicates how strongly an atom of an element attracts electrons in a chemical bond.
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25. Ionic bonds are formed when metals transfer their valence electrons to nonmetals. The oppositely charged ions attract each other to form an ionic bond.
Sodium has one valence electron and chlorine has seven. Sodium want to lose 1 electron and chlorine needs to gain 1.
Forming an Na+ and a Cl- ion – sodium chloride NaCl
Sodium transfers its valence electron to chlorine
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26. The formula for magnesium fluoride is MgF2
A + metal ion is attracted to a – nonmetal ion (opposites attract) forming an ionic compound. We can use Lewis dot structures to represent ionic compounds.
The formula for magnesium fluoride is MgF2
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27. Additional atoms may be necessary to insure that all the ions formed have a stable (noble gas) electron configuration.
What happens when aluminum combines with oxygen to make aluminum oxide?
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28. Aluminum want to lose its 3 valence electrons
Aluminum want to lose its 3 valence electrons. Oxygen needs to gain 2 electrons.
The number of electrons lost by the metal must equal the number of electrons gained by the nonmetal
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29. The formula of aluminum oxide is Al2O3.
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30. Regents Question: 06/02 #51-53
Draw the electron-dot (Lewis) structure of an atom of calcium.
Draw the electron-dot (Lewis) structure of an atom of chlorine.
Draw the electron-dot (Lewis) structure of calcium chloride.
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31. Covalent bonds can be divided into two categories molecular and network
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32. Properties of molecular compounds
Low melting and boiling points (weak attraction between molecules)
Nonelectrolytes: Do not conduct electricity as solids or when dissolved or molten – no charged particles (ions) to move
Solids are soft
Examples: Wax and sugar C6 H12 O6
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33. Network solids High melting and boiling points Hard Non electrolytes
Examples: sand SiO2 and diamond (carbon compound)
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34. The stronger the intermolecular forces, the higher the boiling points and melting points.
Strongest
Ionic Solids
Molecules with Hydrogen bonds
Polar molecules
Nonpolar molecules
Weakest
For nonpolar molecules, the greater the mass, the greater the force of attraction.
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35. Regents Question: 08/02 #33
The table below shows the normal boiling point of four compounds.
Compound Normal Boiling Point (°C)
HF (l)
CH3Cl (l) –24.2
CH3F (l) –78.6
HCl (l) –83.7
Which compound has the strongest intermolecular forces?
(1) HF(l) (2) CH3Cl(l) (3)CH3F(l) (4)HCl(l)
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36. When nonmetals combine with nonmetals, they share electrons
When nonmetals combine with nonmetals, they share electrons. The attraction of two atoms for a shared pair makes a covalent bond.
Electrons are always shared in pairs.
Sharing electrons fills the valence shell with 8 electrons (2 for hydrogen.)
Hydrogen chloride water ammonia methane
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37. Regents Question: 06/02 #61-63
Testing of an unknown solid shows that it has the properties listed below.
(1) low melting point (2) nearly insoluble in water (3) nonconductor of electricity (4) relatively soft solid
State the type of bonding that would be expected in the particles of this substance.
Explain in terms of attractions between particles why the unknown solid has a low melting point.
Explain why the particles of this substance are nonconductors of electricity.
Covalent
The attraction between particles is weak because there are no charged particle.
Molecular substances are non-electrolytes – they do not form ions.
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38. Regents Question: 01/03 #35
Which of the following solids has the highest melting point?
(1) H2O(s)
(2) Na2O(s)
(3) SO2 (s)
(4) CO2 (s) þ
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39. Regents Question: 08/02 #53
Draw an electron-dot diagram for each of the following substances:
A calcium oxide (an ionic compound)
B hydrogen bromide
C carbon dioxide
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40. Regents Question: 06/03 #12
Which type of chemical bond is formed between two atoms of bromine?
Metallic
(2) Hydrogen
(3) ionic
(4) covalent þ
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41. In a multiple covalent bond, more than one pair of electrons are shared between two atoms. (5.2e)
Diatomic oxygen has a double bond O=O (2 shared pairs) because oxygen needs 2 electrons to fill its valence shell
Diatomic nitrogen has a triple bond NN (3 shared pairs) because nitrogen needs 3 electrons to fill its valence shell
Carbon dioxide has two double bonds
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42. Regents Question: 08/02 #17
Which molecule contains a triple covalent
bond?
(1) H 2
(2) N 2
(3) O 2
(4) Cl 2 þ
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43. The electronegativity difference between two bonded atoms is used to assess the degree of polarity in the bond. (5.2k)
Polar covalent bonds form between two different nonmetals
Polar bonds have a negative side and a positive side
The electrons are attracted more to the atom with the higher electronegativity.
The atom with the higher electronegativity is the negative side of the bond.
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44. Symmetrical molecules are not dipoles.
Symmetrical (nonpolar) molecules include CO2 , CH4 , and diatomic elements. ..
Symmetrical molecules are not dipoles.
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45. Asymmetrical (polar) molecules include HCl, NH3 , and H2 O. (5.2l)
The negative side of the molecule is the side that has the atom with the higher electronegativity.
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46. Three types of bonds
Ionic bonds– transfer of electrons- occur between a metal and a nonmetal
Polar bonds– unequal sharing- occur between two different nonmetals
Nonpolar bonds– equal sharing- occur between two of the same nonmetals
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47. Molecular polarity can be determined by the shape of the molecule and the distribution of charge.
Possible shapes
Linear (X2 HX CO2)
Bent (H2O)
Pyramidal (NH3)
Tetrahedral (CH4 CCl4)
A polar molecule is called a dipole. It has a positive side and a negative side – uneven charge distribution.
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48. Physical properties of substances can be explained in terms of chemical bonds and intermolecular forces. These properties include conductivity, malleability, solubility, hardness, melting point, and boiling point. (5.2n)
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49. Regents Question: 01/03 #10
The strength of an atom’s attraction for the electrons in a chemical bond is the atom’s
(1) electronegativity
(2) ionization energy
(3) heat of reaction
(4) heat of formation þ
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50. Regents Question: 06/03 #13
Which of these formulas contains the most polar bond?
(1) H–Br
(2) H–Cl
(3) H–F
(4) H–I þ
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51. Regents Question: 06/02 #8 þ Metallic bonding occurs between atoms of
(1) sulfur
(2) copper
(3) Fluorine
(4) carbon þ
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52. Regents Question: 01/03 #15
The high electrical conductivity of metals is primarily due to
(1) high ionization energies
(2) filled energy levels
(3) mobile electrons
(4) high electronegativities þ
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53. Regents Question: 06/03 #33 þ Which substance contains metallic bonds?
(1) Hg(l)
(2) H2O(l)
(3) NaCl(s)
(4)C6H12O6(s) þ
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54. Regents Question: 01/03 #39
A chemist performs the same tests on two homogeneous white crystalline solids, A and B. The results are
shown in the table below.
The results of these tests suggest that (1) both solids contain only ionic bonds (2) both solids contain only covalent bonds (3) solid A contains only covalent bonds and solid B contains only ionic bonds (4) solid A contains only ionic bonds and solid B contains only covalent bonds þ
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55. Regents Question: 01/03 #57-60
Each molecule listed below is formed by sharing electrons between atoms when the atoms within the molecule are bonded together.
Molecule A: Cl Molecule B: CCl Molecule C: NH3
Draw the electron-dot (Lewis) structure for the NH3 molecule.
Explain why CCl4 is classified as a nonpolar molecule.
Explain why NH3 has stronger intermolecular forces of attraction than Cl2 .
Explain how the bonding in KCl is different from the bonding in molecules A, B, and C.
It is symmetrical. There is an even charge distribution around the molecule.
Ammonia has hydrogen bonds, chlorine is nonpolar.
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KCl is ionic and molecules A, B and C are molecular with covalent bonds.

56. The oxidation states of the elements are available on the Periodic Table of the Elements
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57. To find the formula of a compound, use the criss-cross method
Write the symbol and oxidation state of the metal (lower electronegativiy if both are nonmetals) in the upper right hand corner of the symbol. Positive oxidation state is written first.
Repeat for nonmetal (-) C4+ O2-
Drop the sign C4 O2
Criss Cross C2 O4
Reduce if possible CO2
Although Carbon and Oxygen are both nonmetals, Carbon has a lower electronegativity and therefore uses a positive oxidation number
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58. To find the formula of a compound, use the criss-cross method
Write the symbol and oxidation state of the metal (lower electronegativiy if both are nonmetals) in the upper right hand corner of the symbol. Positive oxidation state is written first.
Repeat for nonmetal (-) C4+ O2-
Drop the sign C4 O2
Criss Cross C2 O4
Reduce if possible CO2
Although Carbon and Oxygen are both nonmetals, Carbon has a lower electronegativity and therefore uses a positive oxidation number
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59. Naming Ionic Compounds
Compounds between a metal and a nonmetal
Name the metal
Name the nonmetal with an IDE ending
Ammonium chloride Aluminum oxide
Barium sulfide Zinc fluoride
If the negative ion is a polyatomic ion
Name the polyatomic ion
Sodium Nitrate Calcium phosphate
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60. Finding the oxidation state of a polyvalent metal
The net charge of a compound must be zero
The number of + charges must equal the total number of – charges
Multiply the oxidation state of the nonmetal by the subscript for the nonmetal
Divide that number by the subscript of the metal
PbO2 the oxidation state of oxygen is –2 we multiply the 2 by the subscript 2 and get 4. Divide the 4 by the subscript for the lead (1) and get 4. The oxidation state for the lead is 4 and the name is Lead(IV)oxide
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61. Regents Question: 06/03 #19
Which formula correctly represents the compo-sition
of iron (III) oxide?
(1) FeO3
(2) Fe2O3
(3) Fe3O
(4) Fe3O2 þ
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62. The Stock System - Naming ionic compounds in which the metal has more than one oxidation state (polyvalent)
Check the Periodic Table to see if the metal has more than one oxidation state if it does…
Determine the oxidation state of the metal
Use the oxidation state of the nonmetal and the subscripts
The oxidation state of the metal is written as a roman numeral in parenthesis after the name of the metal
CuSO4 Copper(II) Sulfate
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63. Naming molecular compounds – compounds between nonmetals
Use a prefix to indicate how many of each element
mono 1 (never used for first element)
di 2
tri 3
tetra 4
CO2 Carbon dioxide
CO Carbon monoxide
N2O4 Dinitrogen tetraoxide
BCl3 Boron trichloride
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64. When using the criss-cross method with polyatomic ions, use parenthesis ( )
Write the symbol and oxidation state of the metal (+ ion) in the upper right hand corner of the symbol.
Repeat for nonmetal (- ion) (NH4) 1+ (PO4) 3-
Drop the sign (NH4) (PO4) 3
Criss Cross (NH4) (PO4) 1
Reduce if possible (numbers outside parenthesis only)
If there is no number following the parenthesis, drop the parenthesis.
(NH4)3 PO4
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65. Polyatomic ions are found on Reference Table E
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