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Feb 20, 2024

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Title: Lab 4 Report- Ionic and Covalent Bonds MOLECULAR STRUCTURE

Introduction: To determine if two unnamed chemicals are ionic or covalent compounds, we will be investigating the physical characteristics of the substances in this experiment, notably their solubility and melting point. Questions: 1. Using the periodic table as a resource, explain the types of atoms that are involved in: a) Ionic bonds When the electronegativity of two atoms differs significantly, ionic bonds are created. Group 7 atoms, for example, have a great tendency to attract electrons due to their high electronegativity. Since group 1 atoms and other atoms with poor electronegativity have a weak ability to attract electrons, they can readily release those electrons to form a chemical bond. The creation of sodium fluoride, or NaF, from a sodium atom and a fluorine atom is an illustration of an ionic bond. The fluorine atom, which has just enough room to take it, picks up the single valence electron that the sodium atom lost during this reaction (1). b) Covalent bonds When atoms share electrons, covalent bonds are created. Nonmetals on the right side of the periodic table, such as H, C, N, O, F, etc., frequently form covalent bonds with one another. This is so that a stable arrangement like the octet rule can be achieved, which calls for the sharing of electrons. Because the electronegativity of two atoms of the same element (such as H 2 ) is identical, covalent bonds can form between them; these covalent bonds are non-polar. Furthermore, polar covalent bonds can be formed when atoms with various electronegativity form bonds. c) Metallic bonds Metal atoms join to form metallic bonds. These elements (such as Cu, Na Fe, and Al) can be found on the left and middle sides of the periodic table. Metallic connections allow metal atoms to share electrons, allowing electrons to travel freely within the crystal lattice structure and provide metals features like conductivity.

2. Explain why an ionic bond is formed in some cases and a covalent bond is formed in other cases. As part of your explanation, make sure you describe the differences in the two types of bonds and the kinds of atoms that partake in these bonding schemes (from Question 1). The ionic bond is created when the "sharing" of electrons between two atoms is so unequal that an electron from atom A entirely loses to atom B, resulting in a pair of ions. In contrast, the covalent link is created when two atoms can share electrons (2). The difference in electronegativity between two atoms determines whether an ionic or covalent connection will form. When the difference in electronegativity is greater than 2, ionic bonds occur. Normally, ionic bonding forms between metals and nonmetals. An electron is "entirely" transported from one atom to another in an ionic bond; the word "entirely" is a condition because an electron transfer is never fully transferred. When the difference in electronegativity is less than two, or when both atoms need to share electrons to reach their stable state, covalent bonds are formed. Covalent bonds often comprise nonmetal + nonmetal or nonmetal + hydrogen atoms. 3. Explain why ionic solids are conductive when they’re dissolved in water, but molecular solids are not. If you melted the two types of materials, would molten salt or molten molecular compounds be conductive? Because their ions are free to move around, ionic compounds conduct electricity when they are molten (liquid) or in an aqueous solution (dissolved in water). Ions in ionic compounds are maintained in fixed locations and are unable to move, therefore they cannot conduct electricity when solid (3). Essentially, ionic solids can conduct electricity when they are dissolved in water (a polar solvent) because the ions in the solid break into cations and anions that move and carry an electric charge. Due to the polarity of water molecules, the delta-positive H atoms draw positive anions while the delta-negative O atoms draw cations. The ions are encircled by the water molecules, which enable them to move around freely and transport their electric charge in the solution. Unlike ionic solids, which break down into ions when dissolved in water, molecular solids often retain all their individual molecules. Previously, intermolecular forces rather than ionic bonds held them together. As a result, there are no ions that are free to float in water and no charges that can conduct electric currents. Molten salts will conduct electricity, while molten molecular compounds will not. According to a related theory, at a high temperature, the solid's ionic bonds dissolve, transforming it into a

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liquid where the ions can flow around freely and transfer charge. Molten molecular compounds, however, do not separate into free-floating charged ions. 4. The simulation gave you the octet rule as the ultimate target for each atom when building Lewis Dot structures. Your course material does not agree that the Octet rule should be the ultimate target. In the table below, draw two Lewis dot diagrams. One, enforcing the Octet rules and a second, enforcing the “lowest charge” rules from your course notes. Below the table, for each species tell which model is the better one and explain why it’s better than the other model you drew of the same species. Species Octet Rule Lowest Charge Rule CO Sulphate SO 4 2- Carbonate CO 3 2- PCl 3

PCl 5 N/A SF 4 N/A 5. Explain why metals and ionic solids have higher melting points than covalent molecular solids (like sugar). Using your explanation above, where do you think the melting points of covalent network solids would fit in (higher or lower in between)? The melting temperatures of metals and ionic solids are often greater than those of covalent molecular solids due to variations in the types and structures of bonds. Strong electrostatic interactions between ions with opposing charges are present in ionic compounds. Ionic compounds have a high melting point because it takes a lot of energy to break up the ionic bonding caused by the huge number of ions in the ionic lattice. Metals have a high melting point because they are massive lattice structures with many electrostatic forces to be broken. Bonds between atoms in covalent compounds share electrons. They have lower melting points because they are easier to break due to the sharing of electrons. Covalent solids (sugar) are covalent compounds, and no ions are present. Molecules are held together by weak van der Waal forces and hydrogen bonds so that is why they have low melting points. Compared to covalent molecular solids, covalent network solids, like diamond or quartz, typically have higher melting temperatures. Their structures have a dense network of covalent connections that are strong and difficult to break, giving rise to higher melting points. Covalent network solids are on the higher end of the melting point spectrum because their melting values are often greater than those of covalent molecule solids.

References: (1) LumenLearning. (n.d.). The ionic bond . Introductory Chemistry. https://uen.pressbooks.pub/introductorychemistry/chapter/the-ionic-bond/ #:~:text=One%20example%20of%20an%20ionic,enough%20space%20to%20accept %20it . (2) Covalent bonds vs Ionic Bonds . Diffen. (n.d.). https://www.diffen.com/difference/Covalent_Bonds_vs_Ionic_Bonds#:~:text=The %20covalent%20bond%20is%20formed,of%20protons%2C%20neutrons%20and %20electrons (3) BBC. (n.d.). Properties of ionic compounds - how do metals and non-metals combine to form compounds? - GCSE combined science revision - OCR 21st Century - BBC bitesize . BBC News. https://www.bbc.co.uk/bitesize/guides/z38smsg/revision/7#:~:text=Conduction%20of %20electricity&text=Ionic%20compounds%20conduct%20electricity%20when,fixed %20positions%20and%20cannot%20move.

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