12th grade. Science Project. PDF

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PROJECT ABOUT BIOLOGY....

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Rumi B Begum egum & F Fatima atima Khan.

Science project

Date Given: Nov-10th_2020. Due Date:Dec-4th_2020.

What are Chemical bonds? Chemical bonds are forces that hold atoms together to make compounds or molecules.Chemical bonds include covalent, polar covalent, and ionic bonds. Atoms with relatively similar electronegativities share electrons between them and are connected by covalent bonds.Atoms with large differences in electronegativity transfer electrons to form ions. The ions then are attracted to each other. This attraction is known as an ionic bond.Chemical bonds are the connections between atoms in a molecule. These bonds include both strong intramolecular interactions, such as covalent and ionic bonds. They are related to weaker intermolecular forces. What are the three primary types of chemical bonds? Introduction to Bonding

Chemical bonding describes a variety of interactions that hold atoms together in chemical compounds.The three types of primary chemical bonds are ionic, covalent, and metallic.

● Ionic Bonds ● Finally, for atoms with the largest electronegativity differences (such as metals bonding with nonmetals), the bonding interaction is called ionic, and the valence electrons are typically represented as being transferred from the metal atom to the nonmetal. Once the electrons have been transferred to the non-metal, both the metal and the non-metal are considered to be ions. The two oppositely charged ions attract each other to form an ionic compound.

● Covalent Bonds ● Chemical bonds are the forces of attraction that tie atoms together. Bonds are formed when valence electrons, the electrons in the outermost electronic “shell” of an atom, interact. The nature of the interaction between the atoms depends on their relative electronegativity. Atoms with equal or similar electronegativity form covalent bonds, in which the valence electron density is shared between the two atoms. The electron density resides between the atoms and is attracted to both nuclei. This type of bond forms most frequently between two non- metals. ● When there is a greater electronegativity difference than between covalently bonded atoms, the pair of atoms usually forms a polar covalent bond. The electrons are still shared between the atoms, but the electrons are not equally attracted to both elements. As a result, the electrons tend to be found near one particular atom most of the time. Again, polar covalent bonds tend to occur between non-metals. ● Metallic bonds ● force that holds atoms together in a metallic substance. Such a solid consists of closely packed atoms. In most cases, the outermost electron shell of each of the metal atoms overlaps with a large number of neighbouring atoms. As a consequence, the valence electrons continually move from one atom to another and are not associated with any specific pair of atoms. In short, the valence electrons in metals, unlike those in covalently bonded substances, are non localized, capable of wandering relatively freely throughout the entire crystal. The atoms that the electrons leave behind become positive ions, and the interaction between such ions and valence electrons gives rise to the cohesive or binding force that holds the metallic crystal together.

Ionic bond: An ionic bond is formed Example: A typical ionically bonded material is NaCl (Salt): when valence electrons are transferred from one atom to the other to complete the outer electron shell.

The sodium (Na) atom gives up its valence electron to complete the outer shell of the chlorine (Cl) atom. Ionic materials are generally very brittle, and strong forces exist between the two ions.

Covalent bond:A covalent bond is formed when the valence electrons from one atom are shared between two or more particular atoms.

Example: Many compounds have covalent bonding, such as polymers. Nylon rope is an example of a material that is made up of polymers. Polymer structures typically are long chains of covalently bonded carbon and hydrogen atoms in various arrangements.

Metallic bond:A metallic bond is formed when the valence electrons are not associated with a particular atom or ion, but exist as a "cloud" of electrons around the ion centers.

In the real and imperfect world, most materials do not have pure metallic, pure covalent, or pure ionic bonding; they may have other types of bonding as well. For example, iron has predominantly metallic bonding, but some covalent bonding also occurs.

This wrench, found in a car shop in Malaysia, has been subjected to much Metallic materials have good electrical abuse and is clearly showing signs of age. and thermal conductivity when compared In its current condition, signs of rust shows to materials with covalent or ionic bonding. that, at a molecular level, its metallic A metal such as iron has metallic bonding. bonding is not perfect and the bending indicates that the original crystalline structure is altered....