Lecture Presentations for Integrated Biology and Skills for Success in Science Banks, Montoya, Johns, & Eveslage Chapter #2 Lecture – pp 12-29 Science, Atoms, Elements, & Subatomic Particles Guiding Principles for the Course Looking at seemingly simple things deeply Conceptual understanding Practical Applications Contextualized Chapter #2 – Learning Objectives By the end of the lecture today, students will be able to: List and define the typical stages in the scientific method. Compare and contrast inductive versus deductive reasoning. Compare and contrast mass versus weight as scientific values Determine the mass of an atom when given the subatomic particles. Define and describe chemistry terms such as element, subatomic particle, proton, neutron, electron, atomic number and atomic mass. Define isotopes and describe differences between isotopes of an element. List the most abundant elements found in the human body. Distinguish the role of valence electrons in chemical reactions Identify and describe any general trends that can be observed in the periodic table of elements including but not limited to atomic mass, ionization energies, and electronegativity values. Scientific Method The Scientific Method involves a series of steps that are used to investigate a natural occurrence It is important to develop a deep understanding of this approach to science as it is a universal way of looking at problems, situations, and phenomena in nature Please become familiar with the flowchart presented here and in your text Deductive vs. Inductive Logic It is very important to define the differences between the two major types of logic that will be used to drive the scientific method in your future observations of nature Deductive logic starts with a statement believed to be true and then goes on to predict what facts would also have to be true to be compatible with that statement In contrast, inductive logic involves taking observations of facts and creating a new theory that is compatible with those observations of facts Control vs. Comparative Experiments There are two main types of experiments used in science: The Controlled Experiment and The Comparative Experiment The purpose of a controlled science experiment is to find out what happens to something if you change something else while you keep all other things unchanged In a controlled experiment you can test only one independent variable This means that you can change only one condition in your experiment The purpose of a comparative experiment is to compare the effect of two or more different things on something In a comparative experiment you can test the effect of a few independent variables but not in the same experimental group where also only one independent variable is allowed as in the case of a controlled experiment What is Biochemistry?? Life is all about the multitude of biochemical reactions that take place all day every day Each part of every living organism is biochemically connected Biochemistry is defined as the study of life on a molecular level Biochemistry covers the biochemical bonds linking atoms to form simple molecular structures and larger structures like DNA, which holds genetic information which flows into RNA and eventually proteins Biochemistry is all about discovering new biochemical structures and determining their functions and interactions with other molecules Biochemistry deals with complex molecular machines, metabolic pathways, and biochemical communications within and in-between organisms The Chemical Elements Element - simplest form of matter to have unique chemical properties Atomic number of an element - number of protons in its nucleus periodic table elements arranged by atomic number elements represented by one- or two letter symbols 24 elements have biological role 6 elements = 98.5% of body weight oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus trace elements in minute amounts Atomic Structure Nucleus - center of atom protons: single + charge, mass = 1 amu (atomic mass unit) neutrons: no charge, mass = 1 amu Atomic Mass of an element is approximately equal to its total number of protons and neutrons Electrons – in concentric clouds that surround the nucleus electrons: single negative charge, very low mass determine the chemical properties of an atom the atom is electrically neutral because number of electrons is equal to the number of protons valence electrons in the outermost shell determine chemical bonding properties of an atom Isotopes Elements are defined by the number of protons in an atom's nucleus For example, an atom with 6 protons must be carbon, and an atom with 92 protons must be uranium Atoms of the same element can have different numbers of neutrons; the different possible versions of each element are called isotopes For example, the most common isotope of hydrogen has no neutrons at all; there's also a hydrogen isotope called deuterium, with one neutron, and another, tritium, with two neutrons. Electron Energy Shells The Bohr Model shows all of the particles in the atom In the center is circles. Each circle represents a single neutron or proton Protons should have a plus or P written on them Neutrons should be blank or have an N In a circle around the nucleus are the electrons. Electrons should have a minus sign or an e Electrons have special rules that they must follow You can’t just shove all of the electrons into the first orbit of an electron Electrons live in something called shells or energy levels. Only so many can be in any certain shell. Nucleus 1st Energy Shell 2nd Energy Shell 3rd Energy Shell The electrons in the outer most shell of any element are called valance electrons The electrons that are more loosely held by the nucleus (the valence electrons, those furthest away from the nucleus) are the ones that are gained, lost, or shared during chemical reactions This is why it is so important to learn and understand about valence electrons So let’s try it…. How to draw a Lithium atom First, look at the Periodic Table Second, determine the number of protons (Look @ the atomic number) Then determine the number of neutrons (Atomic mass – atomic number) Then determine the number of electrons (Look @ the atomic number) 3 Li Lithium 7 So let’s try it…. Protons = 3 3 - + + Li + - - Lithium 7 Electrons = 3 2 in the 1st shell, 1 in the 2nd shell Neutrons = 4 (7-3=4) General Trends of the Periodic Table A trend is a pattern or a repetition of particular properties Trends of the periodic table include: Atomic Mass, Atomic Radius, Net Nuclear Charge, Ion Size, Metallic or Non-Metallic Property, Electro-negativity, 1st ionization energy The periodic table is arranged in a certain way to keep elements with similar properties close together Groups vs. Periods Groups go up and down Periods go left and right Groups share many similarities Periods show periodically (regularly) changing properties The Alkali Metals are in Group 1 but Hydrogen is not in this group. Alkaline Earth Metals are in Group 2 TRANSITIONAL METALS are in Groups 3 - 12 INNER TRANSITIONAL METALS are at the bottom and fit in as shown NON-METALS are at the right hand side of the table Noble Gases are at the far right, group 18 First Trend-Atomic Mass Atomic mass goes higher from element to element, with few exceptions The Group Trend is that atomic mass increases The Period Trend is that atomic mass increases too Because of specific properties, the Periodic Table has a non-regular shape The elements are arranged by properties rather than a way just make the table be uniform in shape Second Trend-Atom Radius If you follow along the periodic table for atomic radius, you find: The Group Trend for atomic radius is that it increases down a group. The Period Trend for atomic radius is that it decreases left to right. SHOWS Atomic Sizes for Groups and Periods Third Trend-1st Ionization Energy 1st ionization energy is the amount of energy needed to remove a valence electron from an entire mole of atoms and make them all into +1 ions For example To turn a mole of Li atoms into a mole of Li+1 ions, it would take 520 kJ/mole FIRST IONIZATION ENERGY FOR SOME SELECTED ATOMS Na 496 kJ/mol Mg 736 kJ/mol Al 578 kJ/mol Si 787 kJ/mol P 1012 kJ/mol Going across the 3rd period, the trend for 1st Ionization Energy is to INCREASE. Fourth Trend – Electronegativity Electronegativity is the amount of pull that an atom has for another electron in a bonding situation Fluorine has the greatest desire of all atoms for that electron gain Fluorine is given the rating of 4.0 on the E-N scale, the highest Electronegativity of all elements Going down a group the trend is towards LOWER E-N values Going across a period the trend is towards higher E-N values It is all about HOW CLOSE IS THE ATOM TO FLUORINE which determines the relative electro-negativity. Exit Quiz 1). Please illustrate and describe the importance of the typical steps that would show up in a flow chart depicting the scientific method. 2). Compare and contrast the differences that exist between mass and weight in science. 3). What are the three main subatomic particles? Be able to accurately assign mass, charge and location for each of these subatomic particles. 4). Define atomic number and atomic mass and be prepared to calculate each value. 5). What is the difference between an electron and a valence electron? Why are valence electrons so important? 6). What is the difference between ionization energy and electronegativity? Are there any trends in the periodic table for these two values? What are they?