Hello and welcome to the introduction of Biology Bio 105. In this lesson, we will be exploring Chapter 2, the Chemical Foundations of Life. In this lecture, you will learn three areas related to the chemical foundations of life. First, you will learn about the general atomic structure of molecules and the four different types of chemicals.
chemical bonding that occurs between different atoms and molecules. Second, we will explore the properties of water. And third, we will look at the different properties of carbon, which is a very important component in living things. We will discuss how matter is defined, the relationship between matter and elements, and the interrelationships of the different components of atoms such as a proton, neutrons, and electrons.
Then we will learn what is an isotope and finally we will discuss an early atomic model of the atom by Neil Bohr which is very useful for our purposes even today to visualize what an atom looks like and behaves. So the main areas in this lecture we will cover are the structure of the atom, what isotopes are, the four different types of chemical bonding found in various types of atoms and molecules, and the properties of water and the properties of carbon. If you take apart any biological system, you will eventually end up with a chemical level of molecules.
because chemical reactions are always occurring in living things and our human body. Quite simply, our bodies are the chemistry of life. As we begin our discussion of chemistry, we must ask, what is matter?
Matter is defined as anything that occupies space and has mass. Matter can be found in three physical states on Earth, solid, liquid, and air. or gas. Understanding what matter is and how it relates to atoms will help you to reach your lesson's objectives. As we begin to discuss matter, we need to discuss some definitions and the first definition we need to talk about is mass.
Mass is the measure of the amount of materials in an object. An element is a substance that cannot be broken down into other substances by chemical reaction. All matter is composed of chemical elements. All life is composed of matter.
Matter is defined as something that occupies space and has mass. Elements are the unique form of matter. They have specific chemical properties and specific physical properties. What is an element? What do we mean when we say something is an element?
Elements are the simplest substances that cannot be broken down into any smaller substances. Element consists of atoms which have all the same number of protons. Each element is designated by a chemical symbol. One or two letters usually, for example, sulfur is designated by a capital S. and calcium is designated by capital C followed by a small a.
The four most common elements found in a living organism is carbon, oxygen, hydrogen, and nitrogen. Most living things have a high degree of oxygen, carbon, hydrogen, and nitrogen in composition in comparison to non-living world. Here we can see that when we're looking at the atmosphere versus the earth's crusts, there is significantly more higher levels of concentrated oxygen, carbon, hydrogen in living things versus non-living things.
We must first discuss that elements are the smallest component or building blocks of an atom. The atom is the smallest unit of matter and retains all the elements' chemical properties. For example, one gold atom has all the properties of gold in the solid metal at room temperature. A gold coin is simply a very large number of gold atoms molded into the shape of a coin and contains small amounts of other elements not known as impurities.
We can't break it down into anything smaller while still retaining the properties of gold. An atom is composed of two regions. You have the nucleus region.
which is the center and has protons and neutrons. The atom's outermost region holds the electrons, which orbits around the nucleus. So atoms contain three subatomic particles, protons, electrons, and neutrons.
The only exception to this is hydrogen, which is made of one proton and one electron with no neutrons. Protons and neutrons have approximately the same mass. Scientists arbitrarily define this amount of mass as one atomic mass unit .
A proton is positively charged whereas a neutron is uncharged. Thus, the number of neutrons in an atom contributes significantly to its mass but not its charge. So what is the relationship between an element and an atom? Each element consists of one kind of atom, and the atom is the smallest unit of matter that still retains all the properties of an element. For example, we talked about how much the atom of gold has all the characteristics and properties of a gold substance, and that there are two areas of the nucleus, the center, which is the nucleus, and the electron orbitals around the nucleus.
So the nucleus is the atom's central core and the electrons are in the orbitals on the outside. So here in this slide is a summary of the three subatomic particles, protons, electrons, and neutrons. When an atom is equal in number to the number of protons and electrons, the net electrical charge is zero and the atom is said to be neutral. Atoms of each element contain a characteristic number of protons and electrons.
The number of protons determine the element's atomic number. Protons generally have a charge of 1, positive 1, whereas electrons have a charge of negative 1 and neutrons do not have a charge at all. The number of protons determines the atomic number. and is used to distinguish one element from another. The number of neutrons is variable in an atom, resulting in isotopes, which are different forms of the same atom.
Isotopes vary only in the number of neutrons they possess together with the number of protons, and neutrons are the determinants of the element's mass number. Here you can see an example where you have aluminum, which has atomic number of 13, and an atomic mass of 26. The atomic number equals the number of protons, and is a distinct number for each of the elements. The periodic table shows the atomic number, and the atomic mass is the mass of the atom. It's the number of protons plus the number of neutrons.
Remember, the number of neutrons can vary in an element, and when they do vary, this different number of neutrons causes isotopes of the element. Electrons don't need to be included in the calculations of the atomic mass because they're so light. The atomic mass is expressed in the atomic mass units, AMU.