Chemical Bonding PDF

# Chemical Bonding ## What is Chemical Bonding? - Chemical bonding is the process by which atoms are held together in compounds. ## Types of Chemical Bonds - There are three main types of chemical bonds: - Ionic bond - Covalent bond - Metallic bond ## The Noble Gases - The noble ga...

# Chemical Bonding ## What is Chemical Bonding? - Chemical bonding is the process by which atoms are held together in compounds. ## Types of Chemical Bonds - There are three main types of chemical bonds: - Ionic bond - Covalent bond - Metallic bond ## The Noble Gases - The noble gases are unreactive, and monatomic, because their atoms already have a stable outer electron shell. - The noble gases are used in providing an inert atmosphere, i.e. Argon in lamps, Helium for filling balloons. ## Halogens - The first halogens (Fluorine and Chlorine) are gases, with a gradual change to liquids and solids down the group. - The atom size increases down the group because of an increasing number of energy levels. - Halogens have diverse uses and play important roles in different fields, such as medicine, industry, household products, and more. ## The Alkali Metals - The Alkali metals are the most reactive of all the metals because they need to lose only one electron to gain a stable outer shell. ## Physical Properties - Luster - How shiny something is - Solubility - How easily something dissolves. Example: Table salt (sodium chloride), which dissolves easily in water - Conductivity - How easily electrical current and heat pass through an object. - Good conductor: Copper wire, which allows electrical current to flow easily. - Poor conductor (insulator): Rubber, which does not allow electrical current to flow easily. - Ductility - How easily something bends. At high temperatures, most metals are ductile. - Non-ductile material: Glass, which is brittle and breaks easily when stretched. ## Chemical Properties - A chemical property describes the ability of a substance to change into a new substance(s). ## Reactivity - Chemicals can react with other substances. Some materials, like metals, can react with acids to produce new substances and release gases. For example, Magnesium reacts with acid, producing visible bubbles of hydrogen gas. ## Flammability - This property determines how easily a substance can catch fire. For example, Paper or gasoline. - When substances burn, they undergo a chemical reaction and turn into different substances. ## Corrosion - The corrosion of iron and steel has a special name: Rusting. - The red-brown substance that forms is called rust. ## Ions - An ion is a charged particle. It is charged because it has an unequal number of protons and electrons. - Ions are formed when atoms lose or gain electrons. - When an atom loses one or more electrons it becomes positively charged because there are more protons than electrons (a cation). - When an atom gains one or more electrons it becomes negatively charged because there are more electrons than protons (an anion). ## Diatomic Molecules - Diatomic molecules are molecules composed of only two atoms, of the same or different chemical elements. ## Elements - Single atoms of elements are not molecules. For example, Oxygen is not a molecule but when Oxygen bonds to itself (O2, O3) or to another element (CO2), molecules are formed. ## Compounds - A compound is a pure substance composed of two or more different elements joined by chemical bonds. - These chemical bonds can only be separated by other chemicals. You can not physically pull, cut, or tear a compound apart. ## Example Tables | Chemical Formula/Symbol | Molecule, Compound? | Visual Representation | Number of Atoms of Each Element (symbol = #) | Total Number of Atoms | Number of Molecules | Number of Elements | |---|---|---|---|---|---|---| | Na2CO3 | Molecule, Compound| | Na=2 atoms, C=1 atom, O=3 atoms | 6 | 1 | 3 | | 3H2O | Molecule, Compound | | H=6 atoms, O=3 atoms | 9 | 3 | 2 | | Co | Element | | Co = 1 atom | 1 | 0 | 1 | | 2Fe2O3 | Molecule, Compound | | Fe=4 atoms, O=6 atoms | 10 | 2 | 2 | ## Example 2 - Dot and Cross Diagrams - Magnesium has an atomic number of 12. Oxygen has an atomic number of 8. Draw dot and cross diagrams to show how the elements bond together and the ions that the elements Mg and O make. ## Periodic Table - Non-metals are on the right side of the periodic table, and metals are on the left. - Down a period of metals, they become more reactive. - With non-metals, going down a period, the non-metal becomes less reactive. ## Groups - Group 1: The Alkali metals - Group 2: The Alkaline Earth metals - Group 7: The Halogens - Group 8 (or Group 0): The Noble Gases ## Let's Practice 1. What type of bonds do halogens tend to form? - a. Ionic - b. Electronegative - c. Covalent - d. All answers are correct 2. Which statement is **NOT** true about the halogens? - a. They are Metals - b. They can be referred to as group 7A - c. They are reactive - d. they exist as Solids, gases and liquids at room temperature 3. All are properties halogens share, **except**: - a. All form only -1 anions - b. All are toxic in their pure form - c. All have 7 valence electrons - d. They form salts when combined with metals 4. Which halogen is the most electronegative? - a. Chlorine - b. All are equally electronegative - c. Fluorine 5. Identify whether the following properties are examples of chemical or physical properties: - a. Melting point - b. Reacts with acid to produce gas - c. Conducts electricity - d. Color