Chemical Bonding PDF

 Learning Points Determine the type of bond share personal insights present between each pair about the association draw the Lewis of atoms and further classify if the given pair of the topic to real...

 Learning Points Determine the type of bond share personal insights present between each pair about the association draw the Lewis of atoms and further classify if the given pair of the topic to real life experiences structure of the forms covalent bond using their electronegativity through a self-made bonding elements. differences; inspirational quote; and  Introduction MOLECULES – CHEMICAL BOND – atoms of the same attraction of atoms or different or ions in a elements combined molecule  Introduction VALENCE ELECTRONS OCTET RULE – An – refer to those element must found in the outermost shell have eight (valence orbitals) of valence electron an atom to reach stability  Three Types of Chemical Bonding ionic covalent metallic Ionic Bonding + - Li F  Elements Metals Ionic bonds form between Metals can be found in the metals and non-metals. middle and on the left hand side of the periodic table. Non-metals Non-metals can be found on the right hand side of the periodic table.  What are ionic bonds? An ionic bond is formed by the transfer of electrons between metal and non- metal. Metal atoms become positively charged ions by losing electrons. Non-metal atoms become negatively charged ions by gaining electrons. Each cation-anion pair is referred to as formula unit. The oppositely charged ions are very strongly attracted to each other. This is known as an electrostatic attraction.  Forming Forming positive ions negative ions Metal atoms lose electrons to form Non-metal atoms gain electrons to positively charged ions with a full form negatively charged ions with a outer shell of electrons. full outer shell of electrons. + - Li Li F F  2+ 2- Mg Handy O tips For elements in groups 1,2 and 3, For elements in groups 6 and 7, the the number of electrons lost is the number of electrons gained is 8 same as the group number (e.g. subtract the group number (e.g. magnesium is in group 2 and forms oxygen is in group 6 and forms a a 2+ ion). 2- ion).  Sodium chloride Na Cl Chlorine gains an electron from sodium to become a negative ion (-1). Sodium loses an electron to become a positive ion (+1). Both + - ions now have a full outer shell of electrons and the ionic Na Cl compound sodium chloride is formed.  Li O Li Lithium oxide Each lithium atom loses an electron to become a positively charged ion (1+). The oxygen + 2- atom gains two electrons to become a negatively charged ion 2 Li O (2-).  Ionic lattice + - + An ionic compound is a regular repeating structure of ions known as - + - a giant ionic lattice. The lattice is composed of a repeating pattern of oppositely charged ions held together + - + by strong electrostatic attractions.  Conduction Ionic compounds can conduct electricity when they are either melted or dissolved in water to form an aqueous solution. In these states, the ions are free to move from place to place. Ionic compounds cannot conduct electricity when solid as their ions are in fixed positions.  Melting and boiling points Ionic compounds consist of oppositely charged ions held together by strong electrostatic attractions. A lot of energy is required to overcome these strong attractions, hence the high melting and boiling points. Covalent Bonding F F  Elements Covalent bonds form in most non-metal elements and in compounds formed between non-metals. Non-metals Non-metals can be found on the right hand side of the periodic table.  H Cl Molecules O These are examples of covalent molecules. Some are elements H H (substances made of the same type of atom) and some are compounds H H (substances made of two or more types of atom). Cl Cl  Electron Rules Recap He Ne The shells must be filled in order of closest to the nucleus, to furthest from the nucleus. When reacting, the aim is for an atom to achieve a full outer shell. This means the desired electron Two electrons Eight electrons configuration is the same as a noble can occupy the can occupy the gas e.g. like helium and neon shown to first shell. other shells. the left.  What are covalent bonds? A covalent bond is formed when two atoms share a pair of electrons. The electrons which contribute towards a covalent bond, are found in the outer shells of the atoms. Usually each atom contributes one electron, but some atoms can react to make multiple covalent bonds.  Nonpolar Covalent Bond A bond in which the electrons are equally shared by the bonded atoms. This means that electrons spend the same length of time in the locality of each atom.  Flourine Each fluorine atom has 7 electrons in the outer shell. Each atom needs to achieve a full outer shell of 8. They can each contribute one electron to a covalent bond. Sharing the electrons, means both atoms now have a full outer shell and a simple covalent molecule is made.  Polar Covalent Bond A bond in which the bonded atoms have an unequal sharing of electrons because they are different atoms or elements. This means that electrons stay longer in the locality of one atom than the other where electronegativity is greater.  Water Water is made of two hydrogen atoms and one oxygen atom. Oxygen has 6 electrons in its outer shell and needs to achieve 8 to make a full outer shell. Each hydrogen has 1 electron and needs to achieve 2 to have a full shell. Two covalent bonds can be formed to make the simple covalent water molecule.  Hydrogen fluoride Fluorine has 7 electrons in its outer shell and needs to achieve 8 to have a full outer shell. Hydrogen has one electron. As this electron is in the first shell, hydrogen needs to achieve 2 electrons to have a full shell. The simple covalent molecule of hydrogen fluoride is made by sharing electrons.  Electronegativity A measure of the tendency of an atom to attract electrons toward itself. Electronegativity difference (∆𝑬𝑵) is used to further determine what type of bonding a compound undergoes. Ionic Bond 1.7 and above Polar Covalent Bond 0.5 to 1.6 Nonpolar Covalent Bond 0.4 and below  Electronegativity Difference (∆𝐸𝑁) More Type of Compound Electronegative ∆𝐸𝑁 Atom Chemical Bond NaCl Chlorine 3.0-0.9=2.1 Ionic ICl Chlorine 3.0-2.5=0.5 Polar Covalent None Nonpolar 𝐻2 (same 2.1-2.1=0 electronegativity) covalent  Sample Problem Based on the metallic properties of elements (metal or nonmetal), predict first if the bond between the pair of atom is ionic or covalent. Then, calculate the electronegativity difference between the atoms to further classify the bonds as polar or nonpolar. Determine the more electronegative atom in each pair. a. chlorine and potassium b. chlorine and carbon c. two atoms of chlorine  Solution Predictions: a. Cl (nonmetal), K (metal) --- Ionic Bond b. Cl (nonmetal), C (nonmetal) --- Covalent Bond c. Cl (nonmetal), Cl (nonmetal) ---Covalent Bond More Electronegative Type of Chemical Compound Atom ∆𝐸𝑁 Bond Cl and K Chlorine 3.0-0.8=2.2 Ionic Cl and C Chlorine 3.0-2.5=0.5 Polar Covalent Cl and Cl None 3.0-3.0=0 Nonpolar covalent (same electronegativity)  Exercise Predict first if the bond between each pair of atoms is ionic or covalent. Further classify the covalent bond as either polar or nonpolar using the concept of electronegativity. Determine the more electronegative atom in each pair. 1.Oxygen and Calcium 2.Oxygen and Chlorine 3.Two atoms of Bromine 4.Barium and Chlorine 5.Magnesium and Chlorine  Conduction Simple covalent substances can not conduct electricity. This is because charged particles and free movement are required for electrical conduction to occur. Covalent bonds are fixed and the electrons can not move.  Melting Point Covalent bonds are very strong but there are weak intermolecular forces between molecules which do not require a lot of thermal energy to be overcome. This means that simple covalent substance have low melting points and are often liquid or gas at room temperature. Cl Cl Metallic Bonding  Elements Only metal elements are Metals involved in metallic bonding. Metals can be found in the middle and on the left hand side of the periodic table.  What is metallic bonding? Metals exist in giant repeating structures of positive metal ions surrounded by electrons which have delocalized from the outer electron shells. Strong electrostatic forces exist between the positive metal ions and the delocalized electrons.  Group 2 metals Group 2 metal atoms lose their 2 outer electrons to form 2+ ions. There is a greater number of delocalized electrons. There is a greater difference in charge between the ions and electrons, so stronger electrostatic attractions are formed. In summary, group 2 metals form stronger metallic bonds than group 1 metals.  Conduction Metals are good conductors of electricity and heat. The delocalized electrons are free to move and pass on the electrical charge and thermal energy.  Melting and boiling points Metals have high melting and boiling points. This is because the metallic bonding in giant metallic structures is very strong. The strong electrostatic forces between the positive ions and delocalized electrons requires a high amount of energy to overcome.  Malleability Most pure metals are malleable, which means that they can be bent or hammered into place. The regular structure allows the layers to slide over each other upon impact. Alloys are made of more than two elements. They have a less regular structure which impacts the malleability and ability of layers to slide over each other.  Lustrous appearance Most metals are lustrous (shiny), this is because there are delocalized electrons on the surface of a metal.  Enrichment For enrichment, you may visit the website: https://javalab.org/en/category/chemistry_en/ch emical_bonds_en/. You may enjoy learning while playing through simulations and further understand and practice chemical bonding.