Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Chemical Bonding Name__________________________________Period:______Date:____________ CHEMICAL BONDS & VALENCE ELECTRONS 1) __________________________= an interaction between atoms that holds them together by reducing the potential energy of their electrons 2) ____________________________= a shorthand representation of the composition of a substance using atomic symbols and numeric subscripts (Ex: NaCl, MgCl2, H2O, C6H12O6) 3) Chemical bonding involves the valence electrons of the atoms involved in a___________________________. 4) _____________________________= the electrons available to be lost, gained, or shared in the formation of chemical bonds • For atoms of main group elements, valance electrons are electrons in the _______________________ main energy level. • Use of the periodic table to determine the number of valence electrons for atoms of the main group elements: Group 1 2 13 14 15 16 17 18 Number of Valence Electrons ______________________= a helium atom has ________valence electrons 1 • Electron Configuration of oxygen: 5) In the electron-dot formulas for atoms of main group elements, valence electrons are represented by _________that surround an element’s symbol. 6) Examples of electron-dot formulas for atoms of the main group elements: 2 DETERMINING BOND TYPE 1) __________________= a chemical bond resulting from ________________________________between positive and negative ions a) In a purely ionic bond, one or more electrons are transferred from one atom to another 2) _______________________= a chemical bond resulting from the___________ of electrons between two atoms a) ___________________= a covalent bond in which the bonding electrons are ______________________ by the bonded atoms b) ______________________= a covalent bond in which the bonding electrons are ___________________ by the bonded atoms δ+ δ- 3) Chemical bonds between two unlike atoms are NEVER completely ionic and RARELY completely covalent. Bonds can be anywhere in the range between these two extremes, depending upon how strongly the bonded atoms attract electrons. 3 4) _______________________= a measure of the ability of an atom in a chemical compound to attract electrons 5) The degree to which bonds are ionic or covalent can be ___________________ by comparing the electronegativities of the bonded atoms. 6) The electronegativity difference of two atoms can be used to determine the ionic character of a bond. • Only ___________________values are used for the final electronegativity 7) The scale below can be used to classify the probable bond type between two atoms. a) If the electronegativity difference between two atoms is: • _________________the probable bond type is usually classified as___________________________. • ______________________the probable bond type is usually classified as_______________________. • _____________________the probable bond type is usually classified as __________________. 8) Polar covalent bonds, a closer look: a) In a polar covalent bond electrons are________________________. b) Shared electrons spend MORE of their time near the atom with the _____________________ electronegativity. c) __________________________ (δ+ or δ-) result. A δ- is assigned to the atom with the ________________electronegativity A δ+ is assigned to the atom with the ________________electronegativity d) Ex: An H atom and a Cl atom form a polar-covalent bond resulting in partial charges. 4 9) Determine the electronegativity difference and probable bond type with respect to bonds formed between the following pairs of atoms. Assign partial charges if the probable bond type is polar-covalent. Pair of Atoms Electronegativity Difference Probable Bond Type Partial Charges S and H S and Cs I and I Cl and Br S and Cl Br and F IONIC BONDING AND IONIC COMPOUNDS 1) Characteristics of ionic compounds: a) Ionic compounds are held together by____________________________. b) Ionic compounds usually involve__________________________________. c) Ionic compounds are _____________under normal conditions. d) Ionic compounds consist of a very large number of positive and negative ions (anions and cations) that are combined so that the numbers of positive and negative charges are________________. e) The chemical formula for an ionic compound represents a formula unit, NOT a____________________________. 2) An ionic compound is __________composed of independent, neutral units that can be isolated and examined. 5 3) ____________________= a compound of positive and negative ions (anions and cations) that are combined so that the numbers of positive and negative charges are equal 4) The chemical formula of an ionic compound shows the _______of ions present in a sample of any size. a) Ex: magnesium chloride has the following chemical formula: MgCl2 For every one Mg+2 ion present, two Cl− ions are present. If 13 mol Mg+2 ions are present in a sample, then 26 mol Cl− ions are present in the sample. 5) The chemical formula for an ionic compound represents a formula unit, NOT a molecule. 6) __________________= the simplest collection of atoms from which an ionic compound’s formula can be established 7) __________________= chemical compounds tend to form so that each atom (by gaining, losing, or sharing electrons) contains eight electrons in its outermost occupied main energy level (valence electrons) 8) Electron-dot formulas can be used to illustrate the formation of_________________. a) Use electron-dot formulas to illustrate the formation of ionic bonds involving Na and Cl. 6 b) Use electron-dot formulas to illustrate the formation of ionic bonds involving Ca and F. c) Use electron-dot formulas to illustrate the formation of ionic bonds involving K and O. COVALENT BONDING & MOLECULAR SUBSTANCES 1) Characteristics of molecular substances: a) Molecular substances are held together by___________________________. b) Molecular substances usually involve ONLY ____________________. c) Molecular substances may be ______________________________under normal conditions. d) Molecular substances consist of_______________________. The_________ of different molecules varies greatly. 2) _______________________= a chemical compound whose simplest units are molecules 3) __________________= a neutral group of atoms held to together by ______________________________ 7 a) A single molecule is an individual unit capable of existing on its own. 4) The chemical formula for a molecular compound is called a________________________. 5) _______________________________= a shorthand representation showing the types and numbers of atoms combined in a single molecule a) Ex: hydrogen peroxide; H2O2;________ atoms of hydrogen and _______ atoms of oxygen are held together by covalent bonds b) Ex: glucose; C6H12O6; 6 atoms of carbon, 12 atoms of hydrogen, and 6 atoms of oxygen are held together by __________________ 6) _______________________= a molecule containing only two atoms a) Ex: HCl, O2 7) Certain elements occur naturally as diatomic molecules (you need to know these elements!!) a) They are: H2, O2, N2, Cl2, Br2, I2, and F2 8 ELECTRON-DOT FORMULAS AND STRUCTURAL FORMULAS 1) Electron-dot formulas illustrate the sharing of ________________________ between atoms. 2) Electron pairs: a) _________________= an electron pair NOT involved in bonding b) ______________= an electron pair shared between two atoms 3) Types of covalent bonds: a) ________________________= a covalent bond produced by the sharing of one pair of electrons between two atoms • Ex: H—H or H : H b) ________________________= a covalent bond produced by the sharing of two pairs of electrons between two atoms • Ex: O2 With six valence electrons each, two oxygen atoms can use twelve electrons to satisfy both octets. By sharing one electron from each oxygen, we can't have more than one oxygen's octet satisfied. We'll need to try a different sharing pattern; a double bond will work. c) ____________________= a covalent bond produced by the sharing of three pairs of electrons between two atoms • Ex: N2 With five valence electrons each, two nitrogen atoms can use ten electrons to satisfy both octets. By sharing one electron from each nitrogen, we can't have either nitrogen's octet satisfied. We'll need to try a different sharing pattern; a triple bond will work. 9 d) In general, _________________are _________________and ____________than single bonds. e) In general, __________________are shorter and stronger than___________________. 4) Use electron-dot formulas to illustrate the formation of a Cl2 molecule from two separate Cl atoms. 5) Guide for Writing Electron-Dot Formulas for Molecules: a) Count the ___________number of valence electrons in the molecule. THESE ARE ALL THE ELECTRONS YOU MAY USE! b) Identify the central atom and terminal atoms: H is always a terminal atom C, if present is usually the _____________atom Molecules tend to be somewhat symmetrical (if one atom is different than the others it is usually the central atom) c) Place _____________of electrons between each pair of bonded atoms to form a____________________. d) Add electron pairs around the _____________________to satisfy the octet rule for the terminal atoms. THERE ARE EXCEPTIONS TO THE OCTET RULE! (see below) e) Assign left over electron pairs to the ___________________________. f) Orient atoms so there is _______________ electron pair repulsions around the central atom. (arrange electron pairs as far apart as you can) g) If the central atom has LESS than an octet of electrons, then move one or more lone pairs from the _________________atoms to form multiple bonds (double and triple bonds). oxygen, nitrogen and carbon CAN form ___________________. 10 h) DO THE FOLLOWING FINAL CHECKS: 9 Check that the total number of valence electrons in the molecule is correct. 9 Check that the octet rule is satisfied for all atoms. DON’T FORGET ABOUT THE EXCEPTIONS. 6) EXCEPTIONS to the octet rule: a) _____________________is an exception to the octet rule. In a molecule, hydrogen contains ________electrons in its outermost occupied main energy level. HYDROGEN CAN FORM ONLY A SINGLE BOND AND WILL CONTAIN NO LONE PAIRS! b) ________________and _______________are SOMETIMES exceptions to the octet rule. These atoms sometimes contain less than eight electrons in their outermost occupied main energy level. Remembering that these atoms DO NOT form double and triple bonds will be helpful when determining if they break the octet rule. 7) Guide for Writing Structural Formulas for Molecules and Polyatomic Ions: a) Follow all guides from above except write a __________to indicate every bond pair. b) __________are still used to represent_________________. 8) Guide for Writing Electron-Dot Formulas for Polyatomic Ions: a) Follow the guide from above except: Add a ____________and _______________to the electron-dot and structural formulas Account for ______________when counting valence electrons • A POSITIVE CHARGE indicates you have to _____________electron(s) o Ex: NH4 +1 has ____ valence electrons: N= _______________ H4 = _____________ So now there is _______ and you subtract ______since the ion has a _____charge to get the final total of ___ valence electrons 11 o Ex: NH4 +1 _____________ ____________ • _____________ _____________ A NEGATIVE CHARGE indicates you have to _________electron(s) o Ex: SO4-2 has _____valence electrons S= ________________________ O4 = ________________________ So now there is ________and you add _____since the ion has a _____charge to get the final total of _____valence electrons THE VALENCE SHELL ELECTRON PAIR REPULSION (VSEPR) MODEL 1) The _____________________has proven useful in predicting molecular geometry and bond angles. 2) The VSEPR model assumes that atoms will orient themselves so as to ___________electron pair repulsions around the central atom. 3) Steps to determine molecular geometry and bond angles: a) Draw an electron-dot formula. b) Arrange the electron pairs around the central atom in a way that minimizes repulsion. In other words, put the electron pairs as far apart as possible. c) Determine molecular geometry: d) Predict the bond angles from the molecular geometry. 12 Molecular Geometry Atoms Bonded to Central Atom Lone Pairs Around the Central Atom Predicted Bond Angles Example BeF2 2 0 BeF3 3 0 NH3 3 1 SnCl2 2 1 H2O 2 2 CH4 4 0 13 e) Notice the bond angle distortion for molecules with a molecular geometry of _____________________and ___________(with_____________________). Ex: O3 is considered bent with a predicted bond angle of 120º since there is only 1 lone pair of electrons Ex: H2O is considered bent with a predicted bond angle of 105° since there is 2 lone pairs of electrons VSEPR model assumes that _______________require more room than bond pairs and tend to compress the angles between bond pairs. In general, bond angles of at least _______________provide enough room for lone pairs that significant bond angle distortion does NOT occur. Using The Modeling Kits: Easily shows molecular geometry A spring represents a single bond (one bond pair of electrons) A colored wooden ball represents various atoms When writing dot formulas and structural formulas you still will have to account for lone pair(s) of electrons since models do not account for lone pair(s) Modeling Kit Color Code: White = hydrogen Black = carbon Red = oxygen Green = halogens Orange = nitrogen Yellow = sulfur 14 POLAR vs. NONPOLAR MOLECULES 1) Use the following chart to determine if a molecule is polar or nonpolar. 1. Does the molecule have ANY polar bonds? YES NO The molecule is NONPOLAR 2. Is the electronegativity of all terminal atoms the same? NO YES The molecule is POLAR Note: if the molecule only contains 2 atoms, stop after the first question. 3. Is the molecule “symmetrical”? (Lone pairs on central atom means molecule is asymmetrical) The molecule is POLAR NO YES The molecule is NONPOLAR 15 Complete the following tables as a class. Formula ICl CH3I BeF2 BF3 # of Valence Electrons Electron-Dot Formula Structural Formula Molecular Geometry Predicted Bond Angles NA Polar or Nonpolar? 16 Formula CO2 H2CO NH3 H 2O # of Valence Electrons Electron-Dot Formula Structural Formula Molecular Geometry Predicted Bond Angles Polar or Nonpolar? 17 Formula # of Valence Electrons Electron-Dot Formula Structural Formula Molecular Geometry Predicted Bond Angles Polar or Nonpolar? NA SO2 SO4−2 NA NA NH4+ N2 18 Valence Electrons & Electron-Dot Notation Worksheet 1) Determine the number of valence electrons in one atom of each of the following elements. Also, write the electron-dot notation for each element. a) Na b) F c) Rb d) Ba e) I f) Se g) Al h) C i) Mg j) Si 19 Electronegativity & Probable Bond Type Worksheet 1) Determine the electronegativity difference and probable bond type with respect to bonds formed between the following pairs of atoms. Assign partial charges if the probable bond type is polar-covalent. Pair of Atoms Electronegativity Difference Probable Bond Type Partial Charges (if polar-covalent) H and H S and O H and I K and Br Si and Cl H and F Se and S C and H Na and Cl O and H N and N I and Cl 20 Ionic Bonding & Ionic Compounds Worksheet 1) Use electron-dot formulas to illustrate the formation of ionic bonds involving Li and Cl. 2) Use electron-dot formulas to illustrate the formation of ionic bonds involving Ca and I. 3) Use electron-dot formulas to illustrate the formation of ionic bonds involving K and F. 4) Use electron-dot formulas to illustrate the formation of ionic bonds involving Mg and Br. 21 5) Use electron-dot formulas to illustrate the formation of ionic bonds involving Al and I. 6) Use electron-dot formulas to illustrate the formation of ionic bonds involving Ca and O. 7) Use electron-dot formulas to illustrate the formation of ionic bonds involving Na and S. 8) Use electron-dot formulas to illustrate the formation of ionic bonds involving Al and S. 22 Complete the following table. Formula NO2+ O3 BF4− H2BF Number of Valence Electrons Electron-Dot Formula Structural Formula Molecular Geometry Predicted Bond Angles Polar or Nonpolar? NA NA 23 Formula BeCl2 CH4 NO2− HCl Number of Valence Electrons Electron-Dot Formula Structural Formula Molecular Geometry Predicted Bond Angles NA Polar or Nonpolar? NA 24 Formula Cl2CO CHCl3 NF3 CCl4 Number of Valence Electrons Electron-Dot Formula Structural Formula Molecular Geometry Predicted Bond Angles Polar or Nonpolar? 25 Formula H2 CHI3 H2Te SiO2 Number of Valence Electrons Electron-Dot Formula Structural Formula Molecular Geometry Predicted Bond Angles NA Polar or Nonpolar? 26 Formula H 2S HCN ClO− PH3 Number of Valence Electrons Electron-Dot Formula Structural Formula Molecular Geometry NA Predicted Bond Angles NA Polar or Nonpolar? 27 Formula ClO2− HClO PCl3 OF2 Number of Valence Electrons Electron-Dot Formula Structural Formula Molecular Geometry Predicted Bond Angles Polar or Nonpolar? NA 28 Formula H 3 O+ I2 CF4 SCl2 Number of Valence Electrons Electron-Dot Formula Structural Formula Molecular Geometry Predicted Bond Angles NA Polar or Nonpolar? NA 29 Formula NCl3 Cl2O NH2Cl SiCl3Br Number of Valence Electrons Electron-Dot Formula Structural Formula Molecular Geometry Predicted Bond Angles Polar or Nonpolar? 30 Formula ONCl NO3− SO4−2 SCN− Number of Valence Electrons Electron-Dot Formula Structural Formula Molecular Geometry Predicted Bond Angles Polar or Nonpolar? NA NA NA 31 IONIC COMPOUNDS MOLECULAR COMPOUNDS Ionic Compounds vs. Molecular Compounds 1. What type(s) of elements are usually contained in this type of compound? 2. Under ordinary conditions, in what state of matter would you find this compound? 3. This type of compound can be described as a collection of ________? 4. What type of bond is holding the atoms together? Explain how atoms are held together by this type of bonding? 32 Bonding Basics Worksheet Vocabulary: Use your notes to help you identify the following vocabulary. 1) A __________________________________is a covalent bond produced by the sharing of two pairs of electrons between two atoms 2) ____________________________is a measure of the ability of an atom in a chemical compound to attract electrons 3) _________________________ is a chemical bond resulting from electrostatic attraction between positive & negative ions 4) A _________________ is a neutral group of atoms held to together by covalent bonds 5) __________________________ is a chemical bond resulting from the sharing of electrons between two atoms 6) A _____________________________ is a covalent bond produced by the sharing of three pairs of electrons between two atoms 7) ___________________________ is a covalent bond in which the bonding electrons are shared unequally by the bonded atoms 8) A _________________________is a molecule containing only two atoms 9) _______________________________ is an electron pair shared between two atoms 10) _____________________________ is an interaction between atoms that holds them together by reducing the potential energy of their electrons 11) _______________________________is the simplest collection of atoms from which an ionic compound’s formula can be established 12) ____________________________is a shorthand representation of the composition of a substance using atomic symbols and numeric subscripts (Ex: NaCl, MgCl2, H2O, C6H12O6) 13) ______________________________ is the tendency of compounds to form so that each atom (by gaining, losing, or sharing electrons) contains eight electrons in its outermost occupied main energy level (valence electrons) 14) A ____________________________is a chemical compound whose simplest units are molecules 15) _____________________________ is the outermost electrons available to be lost, gained, or shared in the formation of chemical bonds 16) _______________________________ is an electron pair NOT involved in bonding 17) __________________________ is a covalent bond in which the bonding electrons are shared equally by the bonded atoms 18) A ______________________________ is a covalent bond produced by the sharing of one pair of electrons between two atoms 19) _____________________________ is the atom in the center of the compound, often carbon 33 Concepts: Answer the following questions. 1. When predicting probable bond types, list the ranges for the following: a. Non-polar covalent =______________________________ b. Polar-covalent = __________________________________ c. Ionic = __________________________________________ 2. Which atom is assigned the partial negative charge? 3. Ionic compounds contain what type of elements?_____________________________________ 4. What phase(s) of matter would you most likely find ionic compounds? _______________________ 5. Molecular substances usually involve only what type of elements? __________________________ 6. What phase(s) of matter would you most likely find molecular compounds? _____________________ 7. List the naturally occurring diatomic molecules. ________________________________________________________________ 8. What are the 3 exceptions to the octet rule when constructing electron dot formulas? 9. Use electron dot formulas to illustrate the formation of ionic bonds involving Li and N. 10. Use electron dot formulas to illustrate the formation of ionic bonds involving Na and O. 34 Dot & Structural Formulas: For each of the following formulas determine the number of valence electrons and draw the electron dot formula and structural formula. Number of Formula Valence Electron Dot Formula Electrons Structural Formula PH3 SO3 CS2 CH2O SiCl4 (silicon tetrachloride) 35 BONDING REVIEW WORKSHEET 1) What are valance electrons? a. Where are valance electrons found? 2) What is an ionic bond? 3) What is the difference between a non-polar covalent bond and a polar-covalent bond? 4) What is electronegativity? 5) When predicting probable bond types, list the ranges for the following: a. Non-polar covalent =______________________________ b. Polar-covalent = __________________________________ c. Ionic = __________________________________________ 6) Which atom is assigned the partial negative charge? 7) Ionic compounds contain what type of elements? _________________________________ 8) What phase(s) of matter would you most likely find ionic compounds? 9) What is the octet rule? 10)Molecular substances usually involve only what type of elements?__________________ 11)What phase(s) of matter would you most likely find molecular compounds? 36 12)What are diatomic molecules? List the naturally occurring diatomic molecules. 13)What is the difference between lone pair electrons and bond pair electrons? 14)What are the exceptions to the octet rule when constructing electron dot formulas? 15)What needs to be added to the electron dot and structural formulas for polyatomic ions? __________________________ & ______________________________ 16)List the 6 types of molecular geometry that a compound may exhibit and the predicted bond angle. 17) Use electron dot formulas to illustrate the formation of ionic bonds involving Ca and Cl. 18)Use electron dot formulas to illustrate the formation of ionic bonds involving K and O. 37 Unit Learning Map (10 days): Class: Bonding Mrs. Hostetter Academic Chemistry A - Grade 11 Unit Essential Question(s): Optional Instructional Tools: Why is one atom rarely found by itself in nature? Concept Chemical Bonds Lesson Essential Questions: Why do chemical bonds form? Vocabulary: Chemical bond Chemical formula Valence electrons Concept Bond Types Lesson Essential Questions: How do you determine probably bond type? Vocabulary: Ionic bonds Covalent bond Nonpolar-covalent bond Polar-covalent bond Electronegativity Ionic compound Formula unit Octet rule Molecular compound Molecule Molecular formula Diatomic molecule Guided Notes Lab Materials: Modeling Lab Ionic Compound Lab Concept Electron Dot and Structural Formulas Concept VSEPR Model Lesson Essential Questions: Lesson Essential Questions: How can molecules and polyatomic ions be represented using electron dot and structural formulas? How can the VSEPR model be used to predict molecular geometry and bond angles? Vocabulary: Lone pair electrons Bond pair electrons Single bond Double bond Triple bond Central atom Dot formula Structural formula Vocabulary: VSEPR Model Molecular geometry Bond angles Linear Trigonal planar Bent Tetrahedral Trigonal Pyramidal 38 Bonding Vocabulary: 20) Chemical bond- an interaction between atoms that holds them together by reducing the potential energy of their electrons 21) Chemical formula- a shorthand representation of the composition of a substance using atomic symbols and numeric subscripts (Ex: NaCl, MgCl2, H2O, C6H12O6) 22) Valence electrons- the outermost electrons available to be lost, gained, or shared in the formation of chemical bonds 23) Ionic bonds- a chemical bond resulting from electrostatic attraction between positive & negative ions 24) Covalent bonds- a chemical bond resulting from the sharing of electrons between two atoms 25) Nonpolar-covalent bond- a covalent bond in which the bonding electrons are shared equally by the bonded atoms 26) Polar-covalent bond- a covalent bond in which the bonding electrons are shared unequally by the bonded atoms 27) Electronegativity- a measure of the ability of an atom in a chemical compound to attract electrons 28) Ionic compound- a compound of positive and negative ions (anions and cations) that are combined so that the numbers of positive and negative charges are equal 29) Formula unit- the simplest collection of atoms from which an ionic compound’s formula can be established 30) Octet rule- chemical compounds tend to form so that each atom (by gaining, losing, or sharing electrons) contains eight electrons in its outermost occupied main energy level (valence electrons) 31) Molecular compound- a chemical compound whose simplest units are molecules 32) Molecule- a neutral group of atoms held to together by covalent bonds 33) Molecular formula- a shorthand representation showing the types and numbers of atoms combined in a single molecule 34) Diatomic molecule- a molecule containing only two atoms (Natural = H2,O2, N2, Cl2, Br2, I2, F2) 35) Lone pair electrons- an electron pair NOT involved in bonding 36) Bond pair electrons- an electron pair shared between two atoms 37) Single bond- a covalent bond produced by the sharing of one pair of electrons between two atoms 38) Double bond- a covalent bond produced by the sharing of two pairs of electrons between two atoms 39) Triple bond- a covalent bond produced by the sharing of three pairs of electrons between two atoms 40) Central atom- atom in the center of the compound, often carbon 41) Dot formula- when dots are used to show bond pairs and lone pairs 42) VSEPR Model- (Valence Shell Electron Pair Repulsion Model) has proven useful in predicting molecular geometry and bond angles 43) Molecular geometry- Linear, Trigonal planer, Bent, Tetrahedral, Trigonal pyramidal, and Bent 44) Bond angles- angle at which the bond takes place 45) Linear- 2 atoms bonded to central angle and predicted bond angles is 180° 46) Trigonal planar- 3 atoms bonded to central angle and predicted bond angles is 120° 47) Bent- 2 atoms bonded to central angle, 1 lone pair around the central atom; predicted bond angle is 120° 48) Bent- 2 atoms bonded to central angle, 2 lone pairs around central atom; predicted bond angle is 105° 49) Tetrahedral- 4 atoms bonded to central angle; predicted bond angle is 109.5° 50) Trigonal Pyramidal- 3 atoms bonded to central angle, 1 lone pair around central atom; predicted bond angle is 107° 39