Chem

Unit Topic: Chemical Bonds 

Essential Question: How does the structure of an atom determine the way it will form bonds within compounds and how  do the forces between compounds determine the properties seen in substances?

Concept 1: 

Introduction to Bonding 

Objectives:  

1. Differentiate between the forces  between different substances versus the  forces within a substance. "Intra" forces are those within the molecule that keep the molecule together, for example, the bonds between the atoms. "Inter" forces are the attractions between molecules, which determine many of the physical properties of a substance.

2. Explain what is meant by the statement,  “Bonding is a spectrum.” Pure covalent bonding and ionic bonding can be considered as opposite ends of a bonding spectrum. In a covalent bond, atoms share pairs of electrons. The covalent bond is the result of two positive nucleuses being held together by their common attraction for the shared pair of electrons.

3. Write a sentence to summarize the  connections between chemical bonds,  chemical reactions, and compounds. A chemical bond is a long-term attraction between atoms, ions, or molecules that allows chemical compounds to form. A chemical reaction takes place when one or more compounds are changed into one or more distinct substances, called as products. Examples of substances are chemical elements or compounds.



4. Explain why most atoms form chemical  bonds and why some atoms don’t.  Most atoms need eight electrons to complete their outer shell

5. Explain the difference between what a  chemical formula tells you about an  ionic versus a covalent compound. Ionic compounds are (usually) formed when a metal reacts with a nonmetal (or a polyatomic ion). Covalent compounds are formed when two nonmetals react with each other.

6. Create a chart to distinguish covalent  bonds from ionic bonds. 

7. Create a chart to distinguish the  properties of covalent compounds from  the properties of ionic compounds.  covalent bond

what e- are doing = electrons are being shared

Types of elements that form these bonds = nonmetallic elements

what is formed = molecule

properties of the compound = made up nonmetals sharing e-, molecules that can be solid liquid, or gas. - low melting and boiling points.- cannot conduct electricity when dissolved in water.

Ionic bond

what e- are doing = electrons are being transferred

Types of elements that form these bonds = a metal and nonmetal.

what is formed = ions within an ionic compound

properties of the compound = - crystalline solids. - crystal lattice= network of cations and anions that are mutually attracted to one another. - high melting and boiling points. - can conduct electricity when dissolved in water.

8. Be able to explain what a chemical  formula tells you about a compound  and predict properties of the compound  based on the bonds that hold it  

together. 

9. Be able to identify a bond or a  

compound as ionic or covalent based  on a picture, description, difference in  electronegativity, or example. 

10. Be able to use an element’s location on  the periodic table to predict its  

oxidation number and bonding  

tendencies. 

Practice:  

11. List the number of atoms of each  element in the compounds below. 

a. AlF3 

b. K3P 

c. Ca(ClO3)2 


Al-1 F-3

K-3 P


Vocabulary:  

Chemical bond a force/mutual electrical attraction that holds atoms together in a substance.


Electronegativity A measure of the ability of an atom in a bond to attract electrons


Octet rule atoms will gain, lose, or share electrons in order to hsve 8 e- in their outer energy shell.


Molecule two or more atoms held together by covalent bonds


Salt An ionic compound made from the neutralization of an acid with a base.


Crystal latticeAn ionic compound made from the neutralization of an acid with a base.

Concept 2: 

Ionic Bonds 

Objectives:  

1. Explain the connection between electronegativity  and the formation of an ionic bond. the greater the difference in electronegativity the more ionic the bond will be. Ionic bonds occur when one atoms donates an electron to another atom.

2. Use an example of an ionic compound to explain  the “rule of zero charge”.  MgCl2 is one atom of magnesium with a 2+ charge, and two atoms of chlorine, each with a 1- charge.

1(2+) + 2(1-) = 2+ + 2- = 0

3. Differentiate between binary ionic compounds,  compounds with polyatomic ions, and binary  molecular compounds.  Binary ionic compounds involve ions, usually a metal cation and a nonmetal anion, formed by electron transfer. Compounds with polyatomic ions involve groups of covalently bonded atoms with an overall charge, often combined with metal or nonmetal ions.

4. Explain why it is necessary to include a Roman  numeral when naming an ionic compound with a  transition metal. You cannot determine the charge of a transition metal from the periodic table, so the Roman numeral is necessary to indicate the charge of the metal ion.

5. Give an example of a common compound and  how the properties of the elements that make it up  are different from that of the compound itself. NaCl = sodium chloride

Sodium on its own is extremely explosive when in contact with water.

Chlorine on its own is extremely poisonous.

Together they make table salt, which we can eat. 

6. Be able to illustrate the formation of ionic bonds  using Lewis structures. 

7. Be able to apply nomenclature rules to determine  the chemical formula and the name of an ionic  compound, including those with polyatomic ions  and/or transition metals. 

Practice:  

8. Draw the Lewis structure for the bond that would  form between calcium and chlorine. Then write its  chemical formula and name. 

9. Name the following compounds:  

a. Na2CO3 

b. NH4C2H3O2 

c. BaCl2 

d. Mn(OH)2 

10.Write the chemical formula for the following  compounds:  

a. Magnesium fluoride 

b.Calcium phosphate 

c. Gold (II) carbonate 

d.Lead (IV) sulfate 

Vocabulary:  

Ionic compound A compound made of positive and negative ions that chemically bond in a way that the charges equal out.


Ionic bond  formed between two or more atoms by the transfer of one or more electrons between atoms


Ion Charged atoms


Cation Positively charged atom from losing electrons


Anion Negatively charged atom from gaining electrons


Polyatomic ion A positively or negatively charged, covalently bonded group of atoms


Transition metal Metals that "transition" because they can form many different ions


Covalent bond:the interatomic linkage that results from the sharing of an electron pair between two atoms

Concept 3: 

Metallic Bonds 

Objectives:  

1. Explain what makes a  metallic bond different  from an ionic versus a  covalent. Metallic bonds occur with 2 metals and share a pool of electrons. A ionic bond is a metal and nonmetal. A covalent bond is 2 nonmetals.

2. Explain why the “sea  of e-” forms in metallic  bonds and why this  

makes them good  

electrical conductors. Metallic bonds contain overlapping orbitals. They are good conductors because the lattice allows energy to pass through.

3. Describe the unique  properties that result  

from metallic bonds. EN is low which makes the attraction of e lower. Metals also share lattices when bonding.

4. Give an example of an  alloy. Include what  

metals make it up and  

how its structure aids  

in how the alloy is  

used. An alloy is carbon steel. It is a mix of 99% iron and 0.1-1% of carbon. Wrenches, hammers

5. Be able to identify a  bond or compound as  

metallic based on a  

picture, description, or  example. 

Vocabulary:  

Metallic bond a bond formed by the attraction between positively charged metal ions and the electrons around them


Delocalized electrons the electrons involved in metallic bonding that are free to move easily from one atom to the next throughout the metal and are not attached to a particular atom


Alloy A mixture of two or more metals

  1. Differentiate between the two types of forces at play in substances. "Intra" forces, also known as intramolecular forces, are those that exist within a molecule, holding the atoms together, such as covalent bonds and ionic bonds. In contrast, "inter" forces, or intermolecular forces, are the attractions that occur between separate molecules, influencing physical properties such as boiling and melting points.

  2. Understand the statement, "Bonding is a spectrum." Pure covalent bonding and ionic bonding exist at opposite ends of this spectrum, with varying degrees of electron sharing. In covalent bonds, atoms share pairs of electrons to achieve stability, while ionic bonds involve one atom transferring electrons to another, resulting in oppositely charged ions that attract.

  3. Summarize the relationship between chemical bonds, reactions, and compounds: A chemical bond represents a long-term attraction that allows atoms or ions to come together to form chemical compounds, which participate in chemical reactions to produce new substances, referred to as products.

  4. Discuss the reasons why most atoms form chemical bonds: Most atoms aim to achieve a full outer electron shell, typically consisting of eight electrons (the octet rule), which stabilizes the atom.

  5. Clarify the difference in information conveyed by chemical formulas for ionic versus covalent compounds: While ionic compounds are usually formed between metals and nonmetals and represented with a fixed ratio of ions, covalent compounds form through the sharing of electrons between two nonmetals, represented differently in their chemical formulas.

  6. Create a chart distinguishing covalent bonds from ionic bonds:

    • Covalent Bond:

      • Electrons are shared.

      • Forms between nonmetallic elements.

      • Produces molecules.

      • Characteristics include lower melting/boiling points and non-conductivity in water.

    • Ionic Bond:

      • Electrons are transferred.

      • Forms between metals and nonmetals.

      • Results in ions within a crystal lattice.

      • Properties include high melting/boiling points and electrical conductivity when dissolved.

  7. Differentiate properties of covalent compounds from those of ionic compounds by creating another comparative chart.

    • Covalent Compounds:

      • Formed from nonmetals sharing electrons.

      • Can be solid, liquid, or gas.

      • Generally have low melting and boiling points.

      • Do not conduct electricity when dissolved in water.

    • Ionic Compounds:

      • Comprise ions held in a crystal lattice structure.

      • Generally solid at room temperature.

      • High melting and boiling points due to strong attractions.

      • Conduct electricity when dissolved in water due to free ions.

  8. Explain how to derive information from a chemical formula and predict compound properties based on the bond types, including polarity and bonding strength.

  9. Learn to identify a bond or a compound as ionic or covalent from various representations including pictures, descriptive text, and electronegativity differences.

  10. Use periodic table locations to predict oxidation numbers and bonding tendencies, understanding how the group and period placement influences an element's chemical properties.

Practice:

  1. List the number of atoms of each element in the following compounds.a. AlF3b. K3Pc. Ca(ClO3)2

Answers:

  • Al - 1, F - 3

  • K - 3, P - 1

  • Ca - 1, Cl - 2, O - 6

Vocabulary:

  • Chemical bond: A force/mutual electrical attraction that holds atoms together in a substance.

  • Electronegativity: A measure of an atom's ability to attract electrons in a bond.

  • Octet rule: Atoms will gain, lose, or share electrons to achieve eight electrons in their outer energy level for stability.

  • Molecule: Two or more atoms held together by covalent bonds.

  • Salt: An ionic compound produced from the neutralization of an acid with a base.

  • Crystal lattice: A three-dimensional structure formed by ionic compounds, where cations and anions are arranged in a repeating pattern.

Concept 2: Ionic Bonds

Objectives:

  1. Connect the concept of electronegativity with ionic bond formation: A higher difference in electronegativity between two atoms indicates a greater tendency toward ionic bond formation, as the more electronegative atom exhibits a stronger pull on the electrons.

  2. Use an example like MgCl2 to illustrate the concept of zero charge balance in ionic compounds: Magnesium (2+) combined with two chlorine atoms (1- each) illustrates that the total positive charge balances the total negative charge, leading to a neutral compound.

  3. Differentiate among binary ionic compounds, polyatomic ion compounds, and binary molecular compounds:

    • Binary ionic compounds comprise two elements, one being a metal cation and another a nonmetal anion.

    • Compounds with polyatomic ions include multiple atoms covalently bonded together, carrying an overall charge.

    • Binary molecular compounds consist of two nonmetals that share electrons.

  4. Explain the importance of Roman numerals in naming ionic compounds with transition metals: Since transition metals can have multiple oxidation states, Roman numerals are used in the name to clearly indicate the charge of the metal ion present in the compound.

  5. Provide common examples like NaCl and discuss how the properties of elements differ from the properties of the compound formed: Sodium is reactive with water, and chlorine is a toxic gas; together they form sodium chloride, a stable edible compound.

  6. Illustrate ionic bond formation using Lewis structures to depict electron transfer and ion formation visually.

  7. Apply nomenclature rules to derive both the chemical formula and name for ionic compounds, including those with polyatomic ions and transition metals.

Practice:

  1. Draw the Lewis structure for the bond formed between calcium and chlorine. Write its chemical formula and name.

  2. Name the following compounds:a. Na2CO3b. NH4C2H3O2c. BaCl2d. Mn(OH)2

  3. Write the chemical formula for the following compounds:a. Magnesium fluorideb. Calcium phosphatec. Gold (II) carbonated. Lead (IV) sulfate

Vocabulary:

  • Ionic compound: Composed of charged ions bonded together in a compound that achieves charge neutrality.

  • Ionic bond: Formed through the transfer of electrons resulting in electrostatic attraction between ions.

  • Ion: An atom or molecule with a net charge due to the loss or gain of one or more electrons.

  • Cation: A positively charged ion formed by loss of electrons.

  • Anion: A negatively charged ion formed by gaining electrons.

  • Polyatomic ion: A group of covalently bonded atoms that together have a charge.

  • Transition Metal: Metals in groups 3-12 that can form various oxidation states and ions.

  • Covalent bond: An interatomic bond resulting from the sharing of electron pairs.

Concept 3: Metallic Bonds

Objectives:

  1. Differentiate metallic bonds from ionic and covalent bonds: Metallic bonds arise between two metal atoms which share a 'sea of electrons,' allowing for high conductivity, malleability, and ductility.

  2. Explain the formation of a 'sea of electrons': In metallic bonding, the outer electrons are not confined to any single atom, resulting in a collective pool allowing easy movement and electrical conductivity.

  3. Describe unique properties linked to metallic bonds such as malleability, ductility, and thermal and electrical conductivity due to the presence of delocalized electrons.

  4. Provide examples of alloys such as steel, which are combinations of iron with carbon, enhancing properties like strength and durability for tools like hammers and wrenches.

  5. Identify metallic bonds through images or descriptions, recognizing characteristics such as luster and conductance.

Vocabulary:

  • Metallic bond: A bond characterized by the attraction between the positively charged metal ions and the delocalized electrons.

  • Delocalized electrons: Electrons in metallic bonding that are free to move between atoms, contributing to conductivity.

  • Alloy: A mixture of two or more metals to create a compound with enhanced properties for specific applications.