Chemical Bonding PDF

# Chemical Bonding ## Learning Objective - Describe Chemical Bonding. - Describe the formation of covalent bonds. - Draw dot and cross diagrams for molecular elements such as $H_2$, $O_2$, and $Cl_2$. ## Chemical Bonding - A bond is a force that holds groups of two or more atoms together and m...

# Chemical Bonding ## Learning Objective - Describe Chemical Bonding. - Describe the formation of covalent bonds. - Draw dot and cross diagrams for molecular elements such as $H_2$, $O_2$, and $Cl_2$. ## Chemical Bonding - A bond is a force that holds groups of two or more atoms together and makes them function as a unit. - Chemical Bonding is the type of force that holds two or more atoms together, it is the attraction between positive nucleus and negative electrons. ### There are three types of bonds: - Ionic bond - Metallic bond - Covalent bond ## Why do atoms bond? Atoms bond to other atoms in oder to gain the same arrangement of outer shell electrons as a noble gas atom (Group 0) because it is a stable arrangement. ## Covalent Bonding Covalent compounds are formed when non-metal atoms react together. As these atoms come near each other, their outer electrons are attracted to the nucleus of both atoms and become shared by the atoms. The shared electrons count towards the shells of both atoms and therefore help fill up incomplete electron shells. ## Covalent Bonds Covalent compounds are held together by this sharing of electrons. A pair of electrons shared in this way are known as a **covalent bond**. It is sometimes represented in full bonding diagrams, see figure 1. Often these bonds are just shown as a pair of electrons(XX) or just a line, see figure 2. ### Figure 1 A diagram showing two oxygen atoms sharing 2 electrons. ### Figure 2 A diagram showing the bond between two fluorine atoms represented by XX and a line, both representing a covalent bond. ## Small Covalent Structures Sometimes just a few atoms join together in this way. This produces small covalent molecules, often known as simple molecular structures. ## Giant Covalent Structures Sometimes millions of atoms are joined together by covalent bonds. This produces a rigid 3-D network called a **Giant Lattice**. ## Covalent Bonding and Electron Structures The driving force for covalent bonding is again the attainment of outer electron shells that are completely full. This is achieved by sharing electrons where the shared electrons count towards the outer shells of both atoms. A diagram showing four different covalent bonds, one between two chlorine atoms, one between four hydrogen and a carbon atom, one between 3 hydrogen atoms and a nitrogen atom and one between a hydrogen atom and a chlorine atom. ## Covalent Bonding in Chlorine Chlorine (2, 8, 7) needs one more electron to attain a full electron shell. A diagram showing two chlorine atoms, each having 7 outer shell electrons forming a complete ionic bond together, each with 8 outer shell electrons. ## Covalent Bonding in Hydrogen Chloride Both hydrogen (1) and chlorine (2, 8, 7) needs one more electron to attain a full outer shell. A diagram illustrating two hydrogen chloride molecules, showing how they share electrons to reach a full outer shell. ## Covalent Bonding in Water Hydrogen (1) needs 1 more electron but oxygen (2, 6) needs 2. Therefore, we need 2 hydrogen atoms. A diagram illustrating how 2 hydrogen atoms and one oxygen atom form a covalent bond in order to reach a full electron shell. ## Hydrogen (1) needs 1 more electron - How many does nitrogen (2, 5) need? **3** - How many hydrogens per 1 nitrogen? **3** Draw bonding diagrams for ammonia. A diagram showing two ammonia molecules, showing how the atoms share electrons to form a covalent bond. ## Hydrogen (1) Needs 1 more electron - How many does carbon (2, 4) need? **4** - How many hydrogens per 1 carbon? **4** Draw bonding diagrams for methane. A diagram showing two methane molecules, showing how the atoms share electrons to form a covalent bond. - Copy the atoms below, complete the diagram showing how each atom can achieve full shells. A diagram showing two hydrogen atoms, before and after forming a covalent bond. ## Covalent Bonding - Multiple bonds Mostly electrons are shared as pairs. There are some compounds where they are shared in fours or even sixes. This gives rise to single, double and triple covalent bonds. Again, each pair of electrons is often represented by a single line when doing simple diagrams of molecules. - **CI-CI** Single bond - **O = O** Double bond - **N ≡ N** Triple bond ## Covalent Bonding in Oxygen Oxygen (2, 8, 6) needs 2 more electrons to attain a full electron shell. A diagram illustrating two oxygen atoms, showing how they share electrons to form a covalent bond. ## Covalent Bonding in Nitrogen Nitrogen (2, 8, 5) needs 3 more electrons to attain a full electron shell and forms a triple bond. Draw a bonding diagram of Nitrogen. A diagram illustrating two nitrogen atoms, showing how they share electrons to form a covalent bond. ## Draw ‘dot and cross’ type bonding diagrams for each of the following: 1. Hydrogen fluoride (HF) 2. Hydrogen sulphide ($H_2S$) 3. Ethane, $C_2H_6$ and the carbons are joined by a single covalent bond. 4. Carbon dioxide ($CO_2$) and the carbon oxygen bonds are double bonds. Four diagrams showing the dot and cross bonding type of diagrams for the four respective molecules.