Chemistry 6-9
How do you calculate formal charge?
(#of valence electrons) - (nonbonding electrons) - (bonding electrons / 2) or - (#of valence electrons) - (# of bonds + #of unshared e-) - FC= (group number) - [(number of bonds) + (number of unshared e-)]
Using Lewis symbols, write the reactions showing electrons are lost or gained when calcium and oxygen become ions
---
What is the shared electron pair called?
Covalent bond
Define polar covalent bonding
(((-a covalent bond in which the electrons are NOT shared evenly -the more electronegative atom is able to pull them closer to itself -generally occurs when the electronegativity difference is .5-1.9))) bonds made up of unequally shared electron pairs - the electrons spend more time with one element causes a polar covalent bond
Define solubility
(the ability of one substance to dissolve in another) - the maximum amount of solute that dissolves in a given amount of solvent at a specific temperature
What are the factors that influence boiling and melting points?
1-Molecular mass Larger molecules have higher m.p. and b.p. than smaller molecules as it is more difficult to convert a larger mass to another phase 2-Polarity Polar molecules have higher m.p. and b.p. than nonpolar molecules of similar molecular mass due to their stronger attractive force
What are some examples of incomplete octets?
BF3 and BCl3 and BeH
What are the diatomic elements?
H2, N2, O2, F2, Cl2, Br2, I2 Have No Fear Of Ice Cold Beer - They totally equal sharing
Predict which compound in each following pairs should have the higher melting and boiling points. (and why) H2O and C2H4 CO and CH4 NH3 and N2 Cl2 and ICl C2H6 and CH4 F2 and Br2 CHCl3 and Cl2
H2O because it is polar CO because it is polar NH3 because it is polar ICl because it is polar C2H6 because it has higher molar mass Br2 because it has higher molar mass CHCl3 because it is polar and has higher molar mass
Predict which of the following bonds are polar and if polar use a vector to indicate in which direction the electrons are pilled.
Si - Cl H - C C - C S - Cl C≡N O-S
The ---- the in--molecular force, the --- energy is required leading to --- m.p. of a -L/S- and b.p. of a -L/S-
The greater the intermolecular force, the more energy is required leading to higher m.p. of a solid and b.p. of a liquid
Does NH3 dissolve in water?
Yes, both are polar
Define intramolecular forces +ex
attractive forces within a molecule (chemical bonds)
Define intermolecular forces
forces of attraction between molecules
What is BeH and example of ?
incomplete octet
What the types of octets?
incomplete octet and expanded octet
Trends of electronegativity in the periodic table - what is the most electronegative element
increases across a period decreases down a group -Fluorine
Define incomplete octet
less then eight electrons around an atom other than H
What do intermolecular forces determine?
physical properties such as melting and boiling point
What does "like dissolves like" mean?
polar dissolves polar, nonpolar dissolves nonpolar
What is the symbol used to denote the polarity of a bond?
positive end is a less electronegative atom negative end more electronegative atom attracts the electrons more strongly towards it
Draw the lewis structure of Fluorine
slide 109/ 13
Drraw the polartiy of HCl, H2O, CO2, cyclopropane are they polar or non polar
slide 163/67
Why don't water and oil mix?
water is polar and oil is nonpolar, oil remains insoluble and floats on the surfaces of the water as it is less dense
What are the guidelines for determining polarity
•Molecules that have no lone pair on the central atom, and all terminal atoms are the same are nonpolar •Molecules with one lone pair on the central atom are polar •Molecules with more than one lone pair on the central atom are usually polar
How do we name covalent compounds?
(1. identify if it is covalent or ionic 2. name the 1st element 3. add a prefix if the number is greater than one 4. name the second element 5. add a prefix, even if the number of atoms is one 6. Change the ending to ide) 1.The names of the elements are written in the order in which they appear in the formula 2.A prefix indicates the number of each kind of atom 3.If only one atom of a particular element is present in the molecule, the prefix mono- is usually omitted from the first element Example: CO is carbon monoxide 4.The name starts with the less electronegative element. 5.The stem of the name of the last element is used with the suffix -ide 6.The final vowel in a prefix is often dropped before a vowel in the stem name
Define molecules + characteristics (structure + state)
(2 or more like atoms combined chemically) Compounds characterized by covalent bonding •Not a part of a massive three-dimensional crystal structure •Exist as discrete molecules in the solid, liquid, and gas states
define Lewis structure:
(A structural formula in which electrons are represented by dots; dot pairs or dashes between two atomic symbols represent pairs in covalent bonds.) -A molecular representation that shows both the connections among atoms and the locations of lone-pair valence electrons
Define polyatomic ion
(Ion that has two or more different elements covalently bonded that travel together as a group and have a charge) ions composed of 2 or more atoms bonded together with an overall positive or negative charge - -Within the ion itself, the atoms are bonded using covalent bonds -The positive and negative ions will be bonded to each other with ionic bonds
Define electronegativity
(a measure of the tendency of an atom to attract a bonding pair of electrons) -a measure of the ability of an atom to attract electrons in a chemical bond.
How do electrons arrange themselves?
(as far apart as possible) - All electrons around the central atom arrange themselves so they can be as far away from each other as possible - to minimize electronic repulsion.
Define monatomic ions
(ions formed from a single atom) ions consisting of a single charged atom such as H+ and Cl-.
Define resonance structure
(one of two or more Lewis structures for a single molecule that cannot be represented accurately by only one Lewis structure) - two or more Lewis structures that contribute to the real structure
Define covalent bond
(the attraction of 2 atoms for a shared pair of electrons) attractive force due to the sharing of electrons between atoms - some bonds have characteristics of both types and not easily identified as one or the other
What is formal charge?
(the charge assigned to an atom in a molecule, assuming that electrons in all chemical bonds are shared equally between atoms, regardless of relative electronegativity) - the hypothetical charge on an atom in a molecule or polyatomic ion
define expanded octet
(when an atom has five or six electron pairs surrounding it, rather than four) - an element in the 3rd period or below may have 10 and 12 electrons around it
In resonance structures are there double bonds? and what does the actual structure = ?
- Experimental evidence shows all bonds are the same length, meaning there is not really any double bond. - None of theses three Lewis structures exist, but the actual structure is an average or hybrid of these three Lewis structures
--- Ionic compounds -- slide 118/ 22
------
•Some common names that are used: H2O NH3 C2H5OH C6H12O6
-H2O water -NH3 ammonia -C2H5OH ethanol or ethyl alcohol -C6H12O6 glucose
The best lewis structure will have a formal charge of???
0 or nearly zero
What are the properties of Ionic and covalent compounds?
1- Physical State Ionic compounds are usually solids at room temperature Covalent compounds can be solids, liquids, and gases 2- Melting and Boiling Points Melting point - the temperature at which a solid is converted to a liquid Boiling point - the temperature at which a liquid is converted to a gas Ionic compounds have much higher melting points and boiling points than covalent compounds A large amount of energy is required to break the electrostatic attractions between ions Ionic compounds typically melt at several hundred degrees Celsius 3- Structure of Compounds in the Solid State -Ionic compounds are crystalline -Covalent compounds are crystalline or amorphous - having no regular structure 4- Solutions of Ionic and Covalent Compounds -Ionic compounds often dissolve in water, where they dissociate - form positive and negative ions in solution -Electrolytes - ions present in solution allowing the solution to conduct electricity -Covalent compounds usually do not dissociate and do not conduct electricity - nonelectrolytes -
How do we name an ionic compound if a if the cation of an element has several ions of different charges (as with transition metals) use
1- stock system/ systematic name - roman numerals give the charge of the metal
Predict the formula of the ionic compounds formed from combining ions of the following pairs of elements: 1. sodium and oxygen 2. lithium and bromine 3. aluminum and oxygen 4. barium and fluorine 5. calcium and nitrogen 6. magnesium and bromine 7. aluminum and bromine
1. sodium and oxygen → (Na+ and O2-) →Na2 O 2. lithium and bromine → (Li+ and Br-) →LiBr 3. aluminum and oxygen → (Al3+ and O2-) → Al2O3 4. barium and fluorine → (Ba2+ and F-) →BaF2 5. calcium and nitrogen → (Ca2+ and N3-) →Ca3N2 6. magnesium and bromine → (Mg2+ and Br-) →MgBr2 7. aluminum and bromine→ (Al3+ and Br-) →AlBr3
What are Lewis Structure guidelines?
1.Use chemical symbols for the various elements to write the skeletal structure of the compound 2.•The least electronegative atom will be placed in the central position •Hydrogen always occupies terminal positions •Halogens occupy terminal positions, except when more electronegative elements are present •Carbon often forms chains of carbon-carbon covalent bonds 2.Determine the number of valence electrons associated with each atom in the compound •Use these valence electrons to determine the number of valence electrons around each atom •Polyatomic cations, subtract one electron for every positive charge •Polyatomic anions, add one electron for every negative charge 3.Connect the central atom to each of the surrounding with single bonds 3.Next, complete octets of all the atoms bonded to the central atom •Hydrogen needs only two electrons •Electrons not involved in bonding are represented as lone pairs •After the terminal atoms have an octet, provide the central atom with an octet if valence electrons are still available 5.If there are not enough valence electrons to give the central atom an octet, move lone pair electrons from terminal atoms to form a new bond with the central atom. -Continue to shift the electrons until all atoms have an octet. 6. Recheck that all atoms have the octet rule satisfied and that the total number of valance electrons are used
What is the formula for formal charge?
= (# valence electrons) - (# of bonds + # non bonding/unshared electrons)
What are the names of the following cations and anions: Anion H- F- Cl- Br- I- O2- S2- N3- P3- Cation H+ Li+ Na+ K+ Cs+ Be2+ Mg2+ Ca2+ Ba2+ Al3+ Ag+
ANIONS Hydride ion Fluoride ion Chloride ion Bromide ion Iodide ion Oxide ion Sulfide ion Nitride ion Phosphide ion CATION Hydrogen ion Lithium ion Sodium ion Potassium ion Cesium ion Beryllium ion Magnesium ion Calcium ion Barium ion Aluminum ion Silver ion
Name each of the following compounds: 1.NH4Cl 2.BaSO4 3.Fe(NO3)3 4.CuHCO3 5.Ca(OH)2 6.Na2SO4
Ammonium chloride Barium sulfate Iron(III) nitrate Copper(I) bicarbonate Calcium hydroxide Sodium sulfate
What are the charges of the follwoing: ANIONS Hydride ion Fluoride ion Chloride ion Bromide ion Iodide ion Oxide ion Sulfide ion Nitride ion Phosphide ion CATION Hydrogen ion Lithium ion Sodium ion Potassium ion Cesium ion Beryllium ion Magnesium ion Calcium ion Barium ion Aluminum ion Silver ion
Anion H- F- Cl- Br- I- O2- S2- N3- P3- Cation H+ Li+ Na+ K+ Cs+ Be2+ Mg2+ Ca2+ Ba2+ Al3+ Ag+
Arrange these elements based on their electronegativity. Be, Mg, Ca, Ba
Ba < Ca < Mg < Be
What are some stable exceptions to the octet rule?
BeH2 BF3
How do you predict Geometric Shape Using Electron Pairs?
Bonded Atoms 2 3 4 3 2 Nonbonding Lone Electron Pairs 0 0 0 1 2 Bond Angle 180° 120° 109.5° ~107° ~104.5° Molecular Geometry Linear Trigonal planar Tetrahedral Pyramidal Bent
What is the formal charge for C,N,O, and Halogens
C - Four bonds, no lone pairs N - Three bonds, one lone pair O - Two bonds, Two lone pairs H - One bond, Three lone pairs
What are the common bonding patterns for C, N, O, X (Halogen), and H.
Carbon - 4 bonds Nitrogen - 3 bonds Oxygen - 2 bonds Halogens - 1 bond Hydrogen - 1 bond
What are some common monatomic Aations and Anions?
Cation H+ Li+ Na+ K+ Cs+ Be2+ Mg2+ Ca2+ Ba2+ Al3+ Ag+ Anion H- F- Cl- Br- I- O2- S2- N3- P3-
What are the features of covalent bonds?
Covalent bonds form between atoms with similar tendencies to gain or lose electrons Compounds containing covalent bonds are called covalent compounds or molecules The diatomic elements have completely covalent bonds (totally equal sharing) H2, N2, O2, F2, Cl2, Br2, I2
What are the molecules that violate the octet rule?
Covalent compounds of Be - BeH2, BeF2, BeCl2 Covalent compounds of the IIA group - BF3, BCl3 Elements in period 3 and beyond CAN exceed the octet rule PCl5, SF6, ClF3, XeCl4, XeF2, [BrF4]-
Elements with ----- electronegativity have a ----- ability to --- electrons than do elements with ---- electronegativity.
Elements with high electronegativity have a greater ability to attract electrons than do elements with low electronegativity.
What are some examples of molecules
Examples: NO H2O ICl PCl5 P2O5 NH3
What are the most electronegative elements? and in what order
F>O>N>Cl
Explain the polar covalent bonding in HF - F charge + means? - H charge + means? - This results in --- sharing of --- which is ---
Fluorine = partial negative charge - electron rich δ- Hydrogen = partial positive charge - electron deficient δ + This results in unequal sharing of electrons in the pairs = polar covalent bonds
Arrange these elements based on their electronegativity. Se, Ge, Br, As
Ge < As < Se < Br
What is the formation of H2 - how many electrons does each hydrogen have? - how would it look like if it were an ionic bond? - however whats the case to why its not usually ionic? - Instead what happens? - draw their lewis structure
H + H -> H2 - one electron in its valence shells - slide 106/ 10 However, both hydrogen atoms have an equal tendency to gain or lose electrons Electron transfer from one H to another usually will not occur under normal conditions - Instead, each atom attains a noble gas configuration by sharing electrons H* +H* -> H**H
Name the following common polyatomic cations and anions: Ion H3O+ NH4+ NO2- NO3- SO32- SO42- HSO4- OH- CN- PO43- HPO42- H2PO4- CO32- HCO3- ClO- ClO2- ClO3- ClO4- CH3COO- (or C2H3O2-) MnO4- Cr2O72- CrO42- O22-
Hydronium Ammonium Nitrite Nitrate Sulfite Sulfate Hydrogen sulfate Hydroxide Cyanide Phosphate Hydrogen phosphate Dihydrogen phosphate Carbonate Bicarbonate Hypochlorite Chlorite Chlorate Perchlorate Acetate Permanganate Dichromate Chromate Peroxide (check slides to seee what to memorize)
What are the principal types of chemical bonds?
Ionic bond and covalent bond
What type of bonding does NaCl have?
Ionic bonding
What are each of the molecular geometry for the following: CO2 SO3 CH4 NH3 H2O
Linear Trigonal planar Tetrahedral Pyramidal Bent
Molecules that are polar behave as ---- (meaning? )
Molecules that are polar behave as a dipole (having two "poles" or ends). One end is positively charged the other is negatively charged
What is the formation of NaCl? - use lewis symbols to show how electrons are lost and gained when sodium and chlorine become ions.
Na + Cl -> NaCl Slide 8 - single Slide 104 - all
Write the formula of each of the following compound: 1. Sodium sulfate 2. Aluminum oxide 3. Magnesium phosphate 4. Calcium carbonate 5. Barium chloride 7. Chromium(II) sulfate 8. Ammonium sulfide
Na2SO4 Al2O3 Mg3(PO4)2 CaCO3 BaCl2 CrSO4 (NH4)2S
Do ionic compounds exist as individual units?
No, they do not, they are arranged in a regular three-dimensional repeating array called a crystal lattice structure.
What are covalent compounds typically formed from?
Nonmetals
what will happen when non- polar molecules are placed in an electric field?
Nonpolar molecules will not align themselves in an electric field
what will happen when polar molecules are placed in an electric field?
Polar molecules when placed in an electric field will align themselves in the field.
What are the following an example of? and why? + whats the name •NH4+ •SO42-
Polyatomic ions because they are composed of 2 or more atoms bonded together with an overall positive/ negative charge •NH4+ ammonium ion •SO42- sulfate ion
What is the prefix for atoms in a compound and the number of atoms they are associated with?
Prefix Mono- 1 Di-2 Tri-3 Tetra4- Penta-5 Hexa-6 Hepta-7 Octa-8 Nona-9 Deca-you 10
What is CO32- an example of and what are the different forms?
Resonance structure
What are some examples of expanded octets?
SF4, SeCl4, SF6
Name each of the following compounds: 1.SiO2 2.N2O5 3.CCl4 4.IF7 5.NO 6.PCl5 7.ICl
Silicon dioxide Dinitrogen pentoxide Carbon tetrachloride Iodine heptaflouride Nitrogen monoxide phosphorous pentacholride iodine monochloride Use the prefixes in the names to determine the subscripts for the elements
What does the difference in electronegativity determine? -The - the difference in electronegativity (∆EN ) between two atoms, the - the polarity of their bond
The extent of bond polarity -The greater the difference in electronegativity (∆EN ) between two atoms, the greater the polarity of their bond
Which requires more room bonding or lone pairs? what do they do?
VSEPR Model: Lone pairs require more room than bonding pairs and tend to compress the angles between the bonding pairs.
What is the Lewis symbol? - what is the only thing that participate in bonding and how does this work for the octet rule - What do the number of dots correspond to?
a way to represent atoms using the element symbol and valence electrons as dots -As only valence electrons participate in bonding, this makes it much easier to work with the octet rule. The number of dots used corresponds directly to the number of valence electrons located in the outermost shell of the atoms of the element.
Where are bonding electrons localized in the covalent bond?
around the nucleus
Define Ionic bond
attractive force due to the transfer of one or more electrons from one atom to another. -the strong attractive force between ions of opposite charge
Draw the lewis structure of H20, what is the bond between them? Draw the lewis structure of ch4
both are covalent bonds slide: 110/ 14
Draw the Lewis symbol of Carbon and indicate the bonds that carbon will form when chemically bonded to other atoms.
carbon can form four bonds
Name the cation and anion in each of the following ionic compounds: NaCl Na2O Li2S AlBr3 CaO
cation sodium sodium lithium aluminum calcium anion stem chlor ox sulf brom ox
What is the formal charge of nitrosyl chloride, NOCl
check slide 141/ 45
What type of forces do Ionic bonds have? what kind of orientation?
electrostatic forces which have no specific orientation in space
What is PF5 an example of? why?
expanded octet, phosphorus is a third period element 1- P atom has 5 valence electrons 5 - F atoms have 7 valence electrons each
Compare Ionic vs. Covalent Compounds
slide 135 / 39
Draw the lewis structures for the following: 1. H2O 2. NH3 3. CO2 4. NH4+ 5. N2 6. CH3COO- 7. C2H4 8. SO2 9. NO3-
slide 147/ 51
Name the following ionic compounds: NaCl Na2O Li2S AlBr3 CaO
sodium chloride sodium oxide lithium sulfide aluminum bromide Calcium oxide
Define Nomenclature - What are the types of naming systems?
the assignment of a correct and unambiguous name to each and every chemical compound Two naming systems: 1-Ionic compounds 2-Covalent compounds
For an ion the sum of the formal charge is ?
the charge of the ion
Define chemical bond - What does the attractive force do? - What is responsible for the bond?
the force of attraction between any two atoms in a compound (A-B) This attractive force overcomes the repulsion of the positively charged nuclei of the two atoms participating in the bond. Interactions involving valence electrons are responsible for the chemical bond
Draw the lewis structure for HF - what is the bonding? - what is F and H charged
the two electrons are not shared equally F is somewhat negatively charged H is somewhat positively charged - Its polar covalent bonding
Are covalent bonds directional or in-directional?
they are directional and have a specific orientation in space between the bonded atoms
What is Stock system or systematic name?
uses a Roman numeral following the metal name •Roman numerals give the charge of the metal
Define VSEPR theory
valence shell electron pair repulsion theory to predict the shape of molecules
When can a truly covalent bond occur?
when both atoms are identical
In a neutral molecule, the sum of the formal charges is ?
zero
Name the following ionic compounds: FeCl3 FeCl2 Cu2O CuO
•FeCl3 is iron(III) chloride •FeCl2 is iron(II) chloride •Cu2O is copper(I) oxide •CuO is copper(II) oxide
Which would be more polar, a H-F bond or H-Cl bond?
•H-F ... ∆EN = [EN of F]-[EN of H]= 4.0 - 2.1 = 1.9 •H-Cl ... ∆EN= [EN of Cl]-[EN of H]= 3.0 - 2.1 = 0.9 The HF bond is more polar than the HCl bond
How do we write the names of ionic compounds from the formula of the compound?
•Name the cation followed by the name of the anion. •A positive ion retains the name of the element; change the anion suffix to -ide •Metals that exist with only one possible cation charge are group IA (1+), group IIA (2+), Ag+, Cd2+ , Zn2+ and Al3+
What is the electronegativity difference for a non polar covalent bond, polar covalent, and ionic bond?
•∆EN<0.5 → nonpolar covalent bond •2.0 >∆EN>0.5 → polar covalent bond •∆EN>2.0 → Ionic bond
Use the electronegativity values to classify the bonds in SiO2 as ionic, polar covalent, or nonpolar covalent.
∆𝐸𝑁= [EN of O]-[EN of Si] = 3.5-1.8=1.7 ∆𝐸𝑁 falls in the range of polar covalent bond.
