Elements, Atoms and the Periodic Table
Grade Level		Prospective and practicing K-8 Teachers
Time		Exercises 1-3 take approximately 2 hours. Until very recently, scientists believed that atoms were the smallest unit of matter which existed. It was only by studying atoms, the stuff all matter is made of, that scientists came to be able to split the atom and "look" inside. For the purpose of this lab, it will not be necessary to borrow a linear accelerator. It will be necessary to begin to develop a basic understanding of atoms. What are they? What are some of the more common atoms? Where do they exist in our bodies? In a brief set of exercises, we will explore common atoms, the periodic table, and atomic structure.
To Ponder		1.	Ashes to ashes, dust to dust. How does matter get recycled?
		2.	How can we eat many different kinds of animal and plants and use those materials to construct or our bodies?
		3.	Plants don't eat as we do. How do they construct themselves?
		4.	Why doesn't all the water on earth simply disappear through evaporation?
Supplies		Periodic Table
Objectives		Once you have completed these exercises you should be able to:
		1.	Understand what atoms are and what they are composed of.
		2.	Describe how the components of an atom may vary.
		3.	Identify the distinguishing structural features of an atom and how they affect the atom's properties.
		4.	Read the periodic table of elements.
		5.	Calculate the atomic weight of an atom, given its atomic number.
Background Information		There are 109 known elements. Oxygen, gold, and arsenic are examples of elements in the entire universe. The smallest unit into which an element may be divided while retaining all of the characteristic properties of that element is an atom. Atoms are tiny, tiny invisible particles. All substances on earth are made of different combinations of the 109 elements.
Powerful Idea		An individual atom of gold has all the attributes of the substance, gold. A gold atom, and in fact all atoms, are made up of smaller components called protons, neutrons, and electrons. However, the subunits of an atom of gold do not, by themselves, have the properties of gold. To restate a powerful idea, an atom is the smallest unit into which an element may be divided while retaining all of the characteristic properties of that element. Many non-science majors are 'turned off by' or fearful of studying chemistry. Who cares about invisible stuff? Well, it happens that a little chemistry can be amazingly empowering in helping people to answer practical questions such as: 'How can I lose weight?' 'What happens to a woman's body when she gets pregnant?' 'What happens to my body if I smoke or drink? Thus, it will be rewarding if you keep your mind open and your curiosity peaked during this and subsequent labs. If you do, you are liable to find it interesting! And relatively easy. We only need to know the basic basics in this course.
		A.	Atoms are composed of three types of particles, the neutron, the proton, and the electron.
		1.	Each type of particle has a different charge. A proton has an electrical charge of +1. An electron has an electrical charge of -1. A neutron has no electrical charge associated with it.
		2.	Two of the three particles have significant mass. A proton has a mass of 1 Atomic Mass Unit (AMU). A neutron has a mass of 1 AMU. An electron has negligible mass (zero for our purposes). Note that atomic mass may be conventionally reported as numbers alone, without the AMU designation.
		3.	Location: Two of the three particles are located in the atomic nucleus and the third orbits the nucleus. Neutrons and protons are tightly packed into the middle of the atom, a region called the atomic nucleus (not to be confused with a cell nucleus!). Electrons orbit the atomic nucleus in complex patterns or orbitals which are determined by how many electrons the particular atom has.
		B.	Most, but not all, atoms have equal numbers of protons, electrons and neutrons.
		1.	The number of protons in the atomic nucleus is the primary determining factor for the general characteristics of the atom. Each different element has a different number of protons in its atomic nucleus. Atoms with the same number of protons in the atomic nucleus are the same element, regardless of whether they have the same numbers of neutrons or electrons.
		2.	For example, all atoms with 1 proton are hydrogen, all atoms with 6 protons are carbon, all atoms with 7 protons are nitrogen, all atoms with 8 protons are oxygen, regardless of the numbers of neutrons and electrons they may have associated with them.
		3.	Hydrogen is different from all other atoms in that the hydrogen atom normally does not contain a neutron. That is, the hydrogen atom is composed of one proton and one electron but no neutron.
		4.	Isotopes are atoms of an element which have differing numbers of neutrons in the atomic nucleus. For example, even though oxygen always has eight protons, it may have from seven to ten neutrons, each representing a different isotope of oxygen. The most prevalent and stable form of oxygen contains eight neutrons as well as eight protons and eight electrons, and has an atomic weight of 16. Isotopes in which the number of neutrons is different from the number of protons are often unstable and radioactive.
		5.	Ions result from changes in the number of electrons orbiting the atomic nucleus. In most atoms, the number of electrons is the same as the number of protons. When the number of electrons does not equal the number of protons in the nucleus, that atom will have a positive or negative electrical charge. For example, a hydrogen atom easily gives up its single electron to another atom or molecule and becomes a positively charged hydrogen ion (H+). In the hydrogen atom, a single negatively charged electron and a single positively charged proton give a total or net charge of zero. The charge of the hydrogen ion comes from the fact that it has lost an electron but still has a positively charged proton. Atoms with an electrical charge are called ions.
Exercise 1		Atoms, Isotopes and Ions
To Do		1.	Complete the table below, considering 'normal' atoms only (not ions or isotopes). Table 1. Characteristics of Some Elements Element # Electrons # Protons # Neutrons hydrogen   1   helium 2 2   sodium 11 11   chlorine   17   argon 18 18   carbon   6   nitrogen   7   oxygen   8
Question		2.	What is the atomic weight of the normal oxygen atom? Of the normal argon atom?
		3.	What is the atomic weight of a hydrogen atom? Of a hydrogen ion?
		4.	When table salt (sodium chloride or NaCl) is dissolved in water, its two components separate as they go into solution. Each sodium atom in salt gives one of its electrons to a chlorine atom. As a consequence, the sodium atoms are positively charged and the chlorine atoms are negatively charged. Are they ions or isotopes?
		5.	What is the charge on each one?
		6.	Deuterium or 'heavy hydrogen' is frequently used in scientific research. It contains a neutron as well as a proton in its nucleus. This makes it an _____________ of hydrogen.
		7.	Does deuterium have an electrical charge? Describe your reasoning.
		8.	What is the approximate mass of deuterium?
Exercise 2		Reading the Periodic Table Look at the periodic table of the elements on the next page. Notice the following points:
Background		1.	Each element is identified by an abbreviation (H = hydrogen, Li = lithium, Na = sodium, K = potassium and so on - see the page following the table for a complete list). Find these elements in the table and identify the group to which each belongs. Groups are designated by a Roman numeral at the top of each column. Table 2. Group Identification Atom   Group   hydrogen     lithium     sodium     potassium
		2.	Elements in each group have common structural and functional properties. For example, the elements in Group IA each have one electron in the outer shell of their atoms and are thus highly reactive. They tend to lose this electron in chemical reactions and to become ions with a single positive charge (e.g., H+, Na+, K+). Atoms in Group IIA each have two electrons in their outer orbit which are also easily given up to form ions. What is the charge on these ions? _____________ How would you write the abbreviations for calcium and magnesium ions?
		3.	In the periodic table that follows, the number of protons (and in most cases, also of electrons and neutrons) is designated by the number in the lower left corner of each box in the periodic table (e.g., H has 1, Li has 3, and Na has 11 protons). This is the atomic number of the element. What is the atomic number of: phosphorus (P)? _____________ sulfur (S)? _____________
		4	As noted previously, each neutron and proton has a mass of one, while the weight of each electron is infinitesimal (close to zero). Thus, helium (He ) has an atomic number of 2, meaning it generally contains 2 protons, 2 electrons, and 2 neutrons. Helium has an atomic weight of 4.003, as shown at the top of the box. What is the atomic weight of:
		carbon (C) _____________ nitrogen _____________ oxygen _____________
		5.	Elements are arranged in the periodic table from left to right and top to bottom in order of increasing mass. The table starts with hydrogen (with an atomic number of one) and goes to unnilennium (with an atomic number of 109). There is an element for each atomic number in between, except for 108 which has not yet been observed. What element has an atomic number of 26? ________________ Is this element important in living things? ____ Explain.
		6.	Only the lighter elements occur in living things. In particular, living organisms are composed of about 25 of the elements in the top four rows of the periodic table. For example, what element has an atomic weight of 40.08 and where does this occur in living things?
		7.	Approximately 25 elements occur in living things. Six of these 25 elements are of critical importance in that they comprise the four major groups of molecules found in living organisms: carbohydrates, lipids, proteins and nucleic acids. These elements are called CHNOPS for short.
To Do			Find the six elements in the periodic table and complete the chart below. Learn all you can about these six atoms.
		Table 3. Some Characteristics of CHNOPS Abreviation Atom Atomic Number Atomic Weight Group C carbon       H hydrogen       N nitrogen       O oxygen       P phosphorous       S sulfur
Question		8.	Which of the other five elements in CHNOPS is most like oxygen?
		9.	Which of the other five elements in CHNOPS is most like nitrogen?
		10.	Which element in CHNOPS has the greatest mass?
		11.	Which element in CHNOPS has the least mass?
Describe		12.	Describe how your body obtains oxygen.
		13.	What is the primary means by which your body obtains phosphorus, carbos and fats?
		14.	How does your body obtain the hydrogen it needs?
		15.	Can your body obtain what it needs by eating carbohydrates or fats alone? Which of the CHNOPS elements are completely absent from carbos and fats?
Exercise 3		Electron Orbitals and Reactivity
Review		1.	Electrons revolve around atomic nuclei in specific patterns called orbitals. The first orbital holds up to two electrons. The second and third orbitals hold up to eight electrons each. (Actually it is more complicated than this but we will use the simple model.) The first orbital fills up before any electrons go into the second orbital, the second orbital fills up before any electrons go into the third orbital, and so on. An orbital diagram for phosphorus is shown below. Phosphorus has an atomic number of 15. Thus phosphorus has 15 protons and 15 neutrons in its nucleus with 15 electrons orbiting around the nucleus. Of these 15 electrons, 2 are in the first orbit, 8 are in the second orbit, and 5 are in the third orbit. There are three 'empty' places for electrons in the third orbit. Figure 1. Phosphorus
To Do		2.	Draw an orbital diagram for each of the other five CHNOPS elements and label each one with the name of the element, its atomic number and atomic weight. Drawing 1. Orbitals of Other CHNOPS Atoms
To Do		3.	Use your orbital drawings to fill in the columns in the table below, showing how many electrons each atom has in its outer orbital and how many 'empty slots' remain in the outer orbital.
		Table 4. Bonding Characteristics of CHNOPS Abreviation Atom # Electrons in Outer Shell # Empty Slots # Bonds Formed C carbon       H hydrogen       N nitrogen       O oxygen       P phosphorous       S sulfur
Explain		4.	The last column in the table above shows how many covalent bonds are formed by each atom when they join with other atoms to form molecules. Each covalent bond arises as the result of two atoms sharing a pair of electrons, one donated by each atom. Explain the bonding behavior of each atom in terms of the number of electrons in its outer shell.
			a. Carbon b. Hydrogen c. Nitrogen d. Oxygen e. Phosphorus f. Sulfur
To Do		5.	Group 0 in the right column of the periodic table contains inert, unreactive or noble gases, including helium, neon, and argon. The atomic numbers of these gases are 2, 10, and 18. Use orbital diagramming to explain why these gases are inert.
Question		6.	What atom is drawn below?
		7.	Two elements in Group IA in addition to hydrogen play a critical role in living tissue. What are they, what are their abbreviations, and what do they do? ______________________________    __________ ______________________________    __________
		8.	Carbon in Group IVA forms the backbone of all organic molecules and thus of all intelligent life. The element below it in Group IVA forms the backbone of intelligent machines. What intelligent machines do we mean, and what is the element used to create them?
		9.	Anaerobic organisms often use sulfur for respiration in place of oxygen. Can you give one reason why such a substitution may be possible?
Supplementary Resources		Atkin, Peter. (1987). Molecules.The abstract concept of molecules is related to everyday experiences. The illustrations clarify the explanations. Salem, Lionel. (1987). Marvels of the Molecule.The author describes the formation and behavior of molecules. Although the concepts are complex, the illustrations and explanations make the book understandable and interesting. Chemistry Teaching Resources, Umea University, Sweden URL: http://www.anachem.umu.se/eks/pointers.htm
Related AAAS Benchmarks		Chapter 4: THE PHYSICAL SETTING Section D: Structure of Matter Grade 6-8 (Benchmark 1 of 7) All matter is made up of atoms, which are far too small to see directly through a microscope. The atoms of any element are alike but are different from atoms of other elements. Atoms may stick together in well-defined molecules or may be packed together in large arrays. Different arrangements of atoms into groups compose all substances. Grade 6-8 (Benchmark 3 of 7) Atoms and molecules are perpetually in motion. Increased temperature means greater average energy of motion, so most substances expand when heated. In solids, the atoms are closely locked in position and can only vibrate. In liquids, the atoms or molecules have higher energy, are more loosely connected, and can slide past one another; some molecules may get enough energy to escape into a gas. In gases, the atoms or molecules have still more energy and are free of one another except during occasional collisions. Grade 6-8 (Benchmark 6 of 7) There are groups of elements that have similar properties, including highly reactive metals, less-reactive metals, highly reactive nonmetals (such as chlorine, fluorine, and oxygen), and some almost completely nonreactive gases (such as helium and neon). An especially important kind of reaction between substances involves combination of oxygen with something else as in burning or rusting. Some elements don't fit into any of the categories; among them are carbon and hydrogen, essential elements of living matter.