Accessible Periodic Tables of the Elements for Blind Students
Dennis Fantin, Kristina Pfeiffer, Marc Sutton, Kael Fischer
Introduction
There are many visual representations of the Periodic Table; so many that the basic shape is familiar even to non-scientists. Among blind people however, even among the college-educated, the basic shape and organization of the Table may not be known. This is primarily because, though available, tactile periodic tables have not been widely distributed.
The fact that a great quantity of supporting information about the elements is normally conveyed through hard-to-access lists and data tables accentuates the difficulty faced by the blind student who wishes to learn chemistry. Such tabulated material is normally found in reference books such as the Handbook of Chemistry and Physics, in appendices to general and inorganic chemistry textbooks, or online in such websites as webelements.com. For blind students, such sources are either impossible to use (the Handbook of Chemistry and Physics is not available in audio or Braille formats), or merely very awkward (most chemistry-oriented websites are not developed with audio screen readers in mind). Even when data tables pertaining to chemistry are read aloud by trained readers, such as in textbooks produced by Learning Ally, the material is often not easy to absorb. This is because the indexing is insufficient which makes it difficult to find one’s place in a large data array or to navigate between tables.
To address the problem of insufficient access, we have developed two digital periodic tables, one is in the DAISY file format, and the other is in the Excel file format. Both versions include additional information about the elements in the form of lists and data tables.
Cal Poly DAISY Periodic Table (CP-DPT)
The CP-DPT introduces the periodic table with a series of accompanying lists and data tables pertaining to the elements. It can be used to investigate properties of the elements and also serves as a quick reference guide in situations where the student does not have a computer. This version is in the DAISY (Digital Accessible Information System) format, and is primarily designed to be used with a digital audio player. Such portable audio devices have largely replaced cassette and CD players, and can handle multiple file types including audio (human speech) and text (synthetic speech) formats. The CP-DPT uses synthetic speech. It has also been tested and is compatible with electronic Braille notetakers.
A limitation of the DAISY software is that it does not support navigation in two dimensions. Given this limitation, it is not possible to navigate through the CP-DPT in both the vertical and horizontal directions. It is possible however to navigate forward and back through a 1D data list; accordingly, the CP-DPT is designed to track the elements in order of atomic number from hydrogen to element 118. It also divides the PTE, and all of the data connected with the properties of the elements into individual rows and columns. In all, the file is divided into 795 1D data lists. Because of the structure, size and complexity of the CP-DPT, extensive use is made of page, line and user-defined level indexing to aid navigation.
The CP-DPT consists of an introduction and four other parts. The introduction contains a description of the properties of atoms and elements, followed by an overview of the modern periodic table. It concludes with four representations of the periodic table organized by group and by period with and without the atomic number.
Part One, page 1 to page 118, presents the elements in order of atomic number in which the page number corresponds to the atomic number. Each page displays one list corresponding to one element’s name and 25 associated physical or chemical properties. This section is useful as a quick reference guide.
Part Two, pages 200-225 associates the individual element properties, one property per page, with the periods (rows) of the PTE. For example, on page 205 which is the page associated with boiling point, there are nine lists. Each list contains the names and boiling points of elements from one of the seven periods, followed by the lanthanides and actinides.
Part Three, pages 300 to 325, is analogous to Part Two, except that each page contains lists corresponding to the periodic table groups one-eighteen. Again, each page displays a single property, and each list on a page contains a data set according to group. Parts Two and Three can be used to investigate how individual element properties change across each of the periods and groups of the periodic table, subject matter covered in all introductory chemistry courses.
Part Four, pages 400 to 404, contains alphabetical indices of the elements by element name and by element symbol, with and without the atomic mass.
Cal Poly Excel Periodic Table (CP-EPT)
We used the popular and accessible Microsoft Excel 2010 application for the CP-EPT based on the fact that screen reader manufacturers have worked with Microsoft for many years to make their suite of Office software accessible to blind users. The CP-EPT is a downloadable Excel workbook containing 27 2D Excel spreadsheets. The first sheet (WK1) provides an introduction to the chemical elements, and describes the modern periodic table. WK2 lists the elements numerically in the first column, and presents 25 associated physical and chemical properties to the right of each element. WK3-WK26 display single atomic properties, arranged in the shape of the PTE; these are useful for exploring how individual properties change in context with the PTE’s rows and columns. WK27 lists the elements alphabetically by name and by atomic symbol with and without the atomic mass. This page also contains element lists in numerical order organized by atomic number and atomic mass.
To navigate within a spreadsheet, hold down alt-ctrl and press one of the four arrow keys to move one cell at a time. Alt-ctrl-home moves to the first cell, and alt-ctrl-end moves to the last cell. To move between spreadsheets, use ctrl-pageup and ctrl-pagedown.
The CP-EPT has been tested and performs well with PC Excel versions 2003, 2007, and 2010. With respect to screen readers, the CP-EPT has been tested and works well on PCs using the most common screen reading programs: JAWS for Windows, release 15.0.11024; WindowEyes, release 8.4; and NVDA Release 2014.4. The CP-EPT has also been tested and found to be satisfactory using VoiceOver on the Macintosh Operating System Version 10.9 (Mavericks); and with Amis Version 3.1.3, the free Windows screen reader
Data Sources
The data tables used in the CP-DPT and the CP-EPT are taken from six sources.
- The Handbook of Chemistry and Physics 89th edition, The Chemical Rubber Company, copyright 2008-2009.
- Principles of Modern Chemistry 6th edition, Oxtoby, D.W., Gillis, H.P., Campion, A., copyright 2007.
- webelements.com, Mark Winter, University of Sheffield, and Webelements Ltd, UK, copyright 1993-2014.
- IUPAC.org, Atomic Weights—No Longer Constants of Nature, Coplen, T., Holden, N., copyright 2011.
- http://www.iupac.org/news/news-detail/article/element-114-is-named-flerovium-and-element-116-is-named-livermorium.html.
- Quick Study Academics Advanced Periodic Table of Elements, BarCharts Inc, copyright 2003.
The authors wish to thank the publishers of the above listed sources.
Overview of Atoms and Elements
All matter, both on earth and throughout the universe, is composed of atoms of a small number of elements, or of sub-atomic particles from which the atoms are derived. While an element is composed of one or more atoms of the same type, defined by the element’s atomic number, atoms share common features. An atom is an entity composed of a nucleus and one or more electrons that are electrically bound to, but outside the nucleus. The electrons exist in concentric shells or energy levels, and it is the outer shell electrons known as the valence electrons that are most relevant to the study of chemistry, for it is these outer-shell electrons that engage in chemical bonding.
The nucleus contains both protons and neutrons in close proximity to one another. It also contains virtually all the mass of the atom. If the electron’s mass is defined as 1, the mass of the proton is 1,837 and that of the neutron is 1,839. In other words, the electron’s mass is negligible compared to that of the proton or neutron.
The nucleus is small in addition to being massive. Its diameter is on the order of one femtometer (1 x 10-15 meters), and this is approximately 1/10,000th the diameter of the atom.
The overall charge on the atom is always zero. This is because an atom has the same number of protons as electrons. Each proton carries a charge of plus one, and each electron carries a charge of minus one. Neutrons are uncharged.
The element’s atomic number is defined as the number of protons in the nucleus. The atomic numbers range from 1 to 118, which covers the elements identified to date. For example, the atomic number of Carbon is 6, meaning that there are 6 protons in the nucleus of all carbon atoms. Like all other atoms with the exception of hydrogen, carbon atoms also contain neutrons in their nucleus. There are actually three types of carbon atoms in nature: one with 6 neutrons, one with 7 neutrons, and one with 8 neutrons. They are all carbon atoms however because they contain 6 protons. These three types of carbon atoms are referred to as carbon isotopes. They are sometimes referred to as carbon-12, carbon-13, and carbon-14, where the number, known as the mass number, corresponds to the sum of protons and neutrons in the nucleus. The mass of each of these isotopes also differs according to the number of neutrons that are present.
Some General Features of the Periodic Table
To date, 118 elements have been identified, and these are organized in a compendium chart known as the Periodic Table of Elements, arranged in order of atomic number, the number of protons in the atom’s nucleus. The modern Periodic Table is organized in horizontal rows and vertical columns, in order of increasing atomic number, moving from left to right, row by row but with some irregularities. In what is known as the international system, the rows or periods are numbered 1-7, and the columns or groups are numbered 1-18. There are two additional rows, the lanthanides and actinides, each with 14elements, positioned below the main table.
Periods one, two, and three do not contain elements in every position. That is to say there are gaps in these rows. Period one contains one element on the far left and one on the far right, atomic numbers 1 and 2.
Periods two, atomic numbers 3-10, and three, 11-18, contain eight elements in each row, 2 on the far left and 6 on the far right.
Periods four, atomic numbers 19-36, and five, 37-54, are filled rows with 18 elements in each row.
Period six is a filled row, 55-57 and 72-86. The missing block of elements, 58-71 is split out and forms the top row below the main table, the lanthanide series.
Period seven is also a filled row, 87-89, and 104-118. It is interrupted by the actinide series, 90-103, which forms the second row below the main table.
In considering the overall architecture of the Periodic Table, a question arises as to why the rows are the length they are. In other words, by what logic does one row end and the next begin? The answer relates to what is known as the Periodic Law. This law states that when the elements are arranged in order of atomic number, their chemical and physical properties show repeatable or Periodic trends; thus, one row ends and the next begins, so that elements with similar properties fall together in vertical columns. For example, elements in the left hand column, Group one, with the exception of hydrogen, are all soft, chemically active metals with one valence electron that react violently with water to produce hydrogen gas; while Group two elements are all semi hard metals with two valence electrons that react with nonmetals to form ionic compounds.
A standard periodic table contains three pieces of information about each element: 1. the one or two letter atomic symbol positioned in the middle of the element square; 2. the atomic number, a whole number representing the number of protons in the nucleus, appearing above the atomic symbol; 3. the atomic mass, usually a decimal number appearing below the atomic symbol. The atomic mass represents the average mass of the element’s isotopes, in comparison with the mass of Carbon-12, which is defined to have a mass of exactly 12 atomic mass units (AMU). The atomic mass can also be expressed in units of grams per mole, and this number is numerically equal to the mass of the atom expressed in AMUs.
Many periodic tables also provide labels for four blocks of elements according to the valence-shell electron configuration of the elements in the block. The electron configuration relates to the distribution of electrons within the orbitals of the atoms. The valence-shell electron configuration refers to the arrangement of electrons in the highest occupied energy level. Groups one and two are s-block elements. Groups thirteen-eighteen form the p-block. Groups three-twelve, the transition metals, form the d-block. The lanthanides and actinides, also known as the inner transition elements, below the main table, comprise the f-block.
Further Divisions of the Periodic Table
Groups one-two and thirteen-eighteen are referred to as the main or representative group elements. The chemical behavior of the elements in these eight groups is predictable because the valence, or outer shell electron configuration, of the elements is the same for every element in the group. Four of the groups are often referred to by name. Group one, the alkali metals, group two the alkaline earth metals, group seventeen the halogens, and group eighteen the noble gases.
Group one the alkali metals: with the exception of hydrogen (a diatomic nonmetallic gas), these elements are highly reactive soft metals, with relatively low melting points and boiling points. All elements have one outer electron, and the plus one oxidation state is favored. When reacting with nonmetals, they tend to give up the outer electron to form positively charged ions (cations) in the plus one state.
Group two the alkaline earth metals: these are reactive, relatively soft metals with boiling points and melting points higher than those for the corresponding alkali metals. Elements have two outer electrons. All members have the plus two oxidation state. When reacting with nonmetals, they tend to give up two outer electrons to form plus two cations.
Group seventeen the halogens: fluorine, chlorine, bromine and iodine are diatomic molecules. Fluorine and chlorine are gases, bromine is a liquid, and iodine is a solid at room temperature. These are highly reactive, nonmetallic elements. The minus one oxidation state is the most common for all members. They tend to gain one electron to form minus one1 ions (anions) when reacting with metals.
Group eighteen the noble gases: these are all gases at room temperature, with extremely low melting points and boiling points. Only the elements toward the bottom of the group, krypton, xenon, and possibly radon, can form compounds; otherwise these elements exist in a monatomic state. The noble gases all have electron configurations with a filled valence shell.
Groups three-twelve are known as transition metals, or transition elements. The transition elements differ considerably in physical and chemical behavior from the main-group elements. To begin with, these elements are all metals, and all except mercury, atomic number 80, are solids. One of the most characteristic chemical properties of the transition metals is the occurrence of multiple oxidation states.
The two rows of elements below the table are sometimes referred to as the inner transition elements. There are fourteen elements in each row. The top row consists of elements known as the lanthanides. These are all metals and tend to exist in a +3 oxidation state. The lanthanides are elements 58-71. Logically, the lanthanides belong in period 6, between elements 57 and 72. However, the series is detached and placed below the main table so that the table will fit on a standard 8.5 by 11 inch sheet of paper oriented in a landscape view. If the series were included in period six, the row would consist of 32 elements, and would not fit on the page.
The bottom row of inner transition elements is known as the actinides, and all are radioactive. The actinide series, atomic numbers 90-103, belongs in period 7, between elements 89 and 104. It is separated from the main table in the same way as the lanthanides, due to space considerations.
Metals, Non-Metals, and Metalloids
114 of the 118 elements identified to date have been recognized with official names by the International Union of Pure and Applied chemistry. These include elements 1-112, and 114, Flerovium, Fl; and 116, Livermorium, Lv. Among the known elements, most, approximately 93 are metals. 17 are non-metals, and 8 are metalloids. In the CP-EPT and the CP-DPT the as yet unnamed elements113 and 115, and 117-118are referred to by their atomic number. In some periodic tables by contrast, unnamed elements are referred to with three letter symbols specifying the Greek number of the element.
The metallic elements are located on the left side of the periodic table. Metals share certain common features. They are lustrous, ductile, malleable, good conductors of heat and electricity, and give up electrons easily to form positively charged ions, cations. Aside from mercury, which is a liquid, all of the metallic elements are solids at room temperature.
The non-metallic elements form a block in the upper right hand corner of the table and also include Hydrogen. These elements are above and to the right of a stair step line, which divides metals from nonmetals. Nonmetals are non-lustrous, non-ductile, nonmalleable, poor conductors of heat and electricity, and tend to accept electrons from metals to form negatively charged ions, anions. Depending on the element, nonmetals may be solids, liquids, or gases at room temperature. Seven nonmetals exist in nature as diatomic molecules, two-atom units. These are hydrogen, atomic number 1, nitrogen, atomic number 7, oxygen, 8, fluorine, 9, chlorine, 17, bromine, 35, and iodine, atomic number 53. Though hydrogen is a nonmetal, it is located apart from the other nonmetals on the left side of the table, at the top of group 1.
The elements lying along the stair step line that divide the metals from nonmetals are known as metalloids or semimetals. Their properties are intermediate between metals and nonmetals. The metalloids are boron, atomic number 5, silicon, 14, germanium, 32, arsenic, 33, antimony, 51, tellurium, 52, polonium, 84, and astatine, atomic number 85. Elements adjacent to the metalloids may also have some metalloid-like properties. In other words, the dividing line between metals and nonmetals is somewhat indistinct.