Chemistry of Life Unit 1 Lesson 4 PDF

Chemistry of Life Unit 1 Lesson 4 Chemistry of Life Students will be able to: Describe the structure of atom and name the six elements found in biological molecules. Describe the three main types of chemical bonding. Key Vocabulary: Ani...

Chemistry of Life Unit 1 Lesson 4 Chemistry of Life Students will be able to: Describe the structure of atom and name the six elements found in biological molecules. Describe the three main types of chemical bonding. Key Vocabulary: Anion, Atom, Cation, Chemical level, Compound, Covalent bond, Electron, Element, Hydrogen bond, Ionic bond, Levels of organization, Molecule, Neutron, Nucleus, Periodic table of elements, Proton, Chemistry of Life An organism can be broken down into smaller levels of organization. These levels are pictured to the right. The smallest level of organization is the chemical level where atoms join together to form small molecules. Chemistry of Life The Chemical Level Atoms are the smallest units which make up matter – this is the case in both living and non-living things. The main components of the atom are shown in the diagram to the right: Chemistry of Life The Atom Atoms contain two regions: 1. The nucleus containing positively charged particles known as protons and neutral, uncharged, particles known as neutrons. 2. Electron shells or orbitals contain negatively charged particles. Electrons orbit the nucleus in different energy levels. Chemistry of Life The Atom The forces which operate between the oppositely charged particles - protons and electrons - hold the atom together. Most atoms contain all three types of subatomic particles. Hydrogen atom (H) is an exception because it has one proton and one electron and no neutrons. The number of protons in the nucleus determines the kind of the element an atom is, this is known as the atomic number, while the number of electrons determines how the atom reacts. Chemistry of Life Atomic Number The Atom The number of protons in the nucleus determines the kind of the element an atom is, this is known as the atomic number. Carbon has an atomic number of 6. This means that it has 6 protons and 6 electrons Chemistry of Life Comprehension Check... How many protons do each of these atoms have? 20 7 13 11 9 Ca N Al Na F 40 14.007 26.982 22.99 18.98 Calcium Nitrogen Aluminum Sodium Fluorine Chemistry of Life Comprehension Check... Answers 20 7 13 11 9 Ca N Al Na F 40 14.007 26.982 22.99 18.98 Calcium Nitrogen Aluminum Sodium Fluorine 20 7 13 11 9 Chemistry of Life Elements An element is a substance which is made up of one type of atom. For this reason, elements are called pure substances. There are 94 naturally occurring elements known to scientists. These have been arranged on a chart called the periodic table (shown on the next slide). Chemistry of Life Chemistry of Life The main elements found in living things are: Carbon (C) Hydrogen (H) C P Oxygen (O) O Sulfur (S) Nitrogen (N) H S Phosphorous (P) N Chemistry of Life It is the bonding between the atoms of these six elements that makes all life possible. Chemical bonding involves atoms gaining, losing or sharing electrons in order to form larger structures. This allows them to complete any partially full electron shells and become more stable in the process. Chemistry of Life Molecules vs Compounds: When atoms bond they form molecules and compounds. Molecules are any group of atoms which are chemically bonded together. Compounds are two or more different atoms bonded together. H H H H O A hydrogen molecule Water is both a compound and a molecule Chemistry of Life Comprehension Check Decide if the following or molecules, compounds or both. Chemistry of Life Answers... Molecules Molecules AND compounds Chemistry of Life Types of bonds: Atoms can form three different types of chemical bonds – ionic, covalent, and hydrogen bonds. Chemistry of Life 1. Ionic bonds Ionic bonds are formed when atoms gain or lose electrons and become ions. When an atom donates an electron from its outer shell, it forms a positive ion called a cation. Atoms which accept electrons form negatively charged ions known as anions. Chemistry of Life 1. Ionic bonds Since opposite charges attract, the positive and negative ions are pulled together and form an ionic bond. These bonds are strong and therefore require large amounts of energy in order to be broken. An example of the exchange of electrons between a sodium and chlorine atom can be seen in the diagram below. Chemistry of Life 1. Ionic Bonds Generally, the donation of an electron by one atom cannot happen without an electron recipient, so these two processes of electron donation and electron acceptance must occur at the same time. Certain ions such as sodium, potassium and calcium are referred to electrolytes in biology. These ions are essential for the function of the nervous system, muscle contraction and water balance in the body. Chemistry of Life Comprehension Check... Can you... ✓ Name the three types of bonding? ✓ Define ionic bond? ✓ Draw a diagram to show how an ionic bond forms? Chemistry of Life Comprehension Check: Answers ✓ Name the three types of bonding: Ionic, covalent and hydrogen bonding ✓ Define ionic bond A bond which forms through the loss and gain of electrons ✓ Draw a diagram to show how an ionic bond forms See diagram to the right Chemistry of Life 2. Covalent Bonds The covalent bonds form when electrons are shared between atoms. This is commonly seen in carbon-based molecules and also in water, an essential molecule found in all living things. Chemistry of Life 2. Covalent Bonds In the water molecule, each hydrogen atom shares one electron with the oxygen atom and the oxygen atom shares two electrons (one electron with each hydrogen atom). The shared electrons complete each atom’s outermost (valence) shell, making the water molecule more stable than its component atoms. Chemistry of Life 3. Hydrogen Bonds Hydrogen bonds are relatively weak bonds which require little energy to break. These bonds occur between two molecules as a result of the electrostatic attraction between a proton in one molecule and an electronegative atom in the other. Chemistry of Life 3. Hydrogen Bonds Both covalent and hydrogen bonds can be seen in the section of DNA molecule, shown below, The covalent bonds hold the backbone of the DNA molecule together, whereas the hydrogen Hydrogen Covalent bonds act to stabilize the two bond bond strands allowing it to form a double helix. Chemistry of Life Comprehension Check Can you… ✓ Define covalent bond? ✓ Name the main atom which forms covalent bonds? ✓ Describe how a hydrogen bond differs to a covalent bond? Chemistry of Life Comprehension Check Answers: ✓ Define covalent bond: A bond formed when electrons are shared ✓ Name the main atom which forms covalent bonds? Carbon ✓ Describe how a hydrogen bond differs to a covalent bond? Covalent bonds are strong whereas hydrogen bonds are weak