The purpose of this lab experiment is to practice writing Lewis symbols for elements and monatomic ions while writing Lewis structure for molecules and polyatomic ions. I will also be writing chemical equations using Lewis structures for different reactions involving either ionic compounds or covalent compounds. Lastly, I will I will predict the empirical formulas of ionic and covalent compounds based on the Lewis symbols for their ions and atoms, while also writing Lewis structures for the compound as well. Background
Chemists utilize models in order to better understand the nature of any matter they are studying. These physicals model often allow chemists to better understand the shape and relative size of atoms, molecules, and ions that make up the substance and the spatial relationships amongst all of these components. In these models every atomic nucleus is surrounded by at least one electron, of which only the valence electrons are chemically active. To illustrate this chemists use a model known as the Lewis electron-dot symbol which illustrates both the chemical symbol and the electron dots. The bonds that hold the atoms of a substance together are illustrated through the use of a Lewis structure, which shows the different atoms and their numbers in the species as well as the distribution of all valence electrons. The portion of the Lewis symbol that represents the nucleus and inner, non-valence, electrons of one atom is called the atomic core. In this model the valence electrons are represented by using dots around this atomic core symbol. When putting together this Lewis symbol the model is constructed by arbitrarily placing the electron dots one at a time on each of the four sides of the atomic core until all of the valance electrons are represented. In chemical reactions, electrons are shared and transferred between atoms which produces ionic or covalent compounds. A compound made up of a combination of positive and negative compounds is known as an ionic compound. Subsequently, the attraction that holds these oppositely charged ions together is known as an ionic bond. In the species where there is bonding between atoms in a molecule or polyatomic ion, pairs of electrons are shared between atoms which form a covalent bond. These atoms that are joined by covalent bonds then form covalent compounds. When the outer electron levels of atoms reach their maximum of eight electrons they are referred to as an octet, thus we say that this configuration is in accordance with the octet rule. When a hydrogen atom has only two electrons, this configuration is then in accordance with the duet rule. We can also use Lewis structures to predict the empirical formula of a substance from the reaction of two elements. An example would be the reaction between silicon and hydrogen, where each silicon has an electron octet and each hydrogen has an electron duet. With that ratio being four hydrogen atoms bonding to each silicon atom, the empirical formula can be computed to be SiH4. In this experiment, I will write chemical equations using Lewis symbols and Lewis structures to represent reactants and products. Based on the Lewis symbols of selected elements, I will determine the possible empirical formula and Lewis structure for these products.
I will begin this lab by filling in the Lewis symbols for the third period elements that are listed. I will then write the Lewis symbol for the listed ions and construct the Lewis structure model for the ionic compound potassium chloride using the following steps; identify the number of valence electrons, identify the atomic cores for potassium and chloride ions, writing the Lewis symbol for each one, Writing the Lewis structure, and identifying the difference in structure between the two. I will then construct the Lewis structure model for the covalent compound hydrogen sulfide using the same before mentioned steps. Next I will construct the Lewis structure model for the covalent compound sulfur difluoride by identifying the number of valence electrons, arranging the atomic cores, rewriting the atomic cores with electron pairs, and writing the Lewis structure while distributing the remaining valence electrons so that all three atoms are in accordance with the octet rule. Once completed I will then construct the Lewis structure model for the covalent compound methylene chloride using the same steps previously listed. I will then construct the Lewis structure model for the covalent compound carbon tetrachloride by identifying the total number of valence electrons, writing the atomic core for the element with the central atom surrounded by the remaining atomic cores, writing the Lewis structure after distributing the remaining valence electrons so that each chlorine atom has an electron octet. Once completed I will then utilize these same steps to construct the Lewis structure for the covalent compound phosgene while considering the possibility of a multiple bond between two of the atoms if I have trouble placing all of the valance electrons. I will then construct the Lewis structure for the covalent compound silicon dioxide using this same process, while also writing the Lewis structure for the hydrosulfide ion and covalent molecule nitrogen in individual boxes while identifying the number of valence electron for each structure. Once completed, I will then fill in the table given by writing the empirical formula and the Lewis structure for potassium iodine, calcium fluorine, and sulfur chlorine. I will do this by assuming that the first two pairs of elements react to form iconic compounds while the third forms a covalent compound. I will also refer to the periodic table to determine the number of valence electrons for each of the elements given. Once this table is complete I will then write both an equation using Lewis structures and a balanced chemical equation for the following reactions; silicon atoms and chlorine molecules, lithium atoms and bromine molecules, and ethylene molecules and chloride molecules. Once completed I will then predict the empirical formula and Lewis structure of both the hydride of selenium and hydride of tin.