PERIODIC TABLE I

INTRODUCTION Open just about any chemistry book and you will see a copy of the periodic table of the elements. The periodic table is a framework for classifying information about the properties of all known elements on Earth.

INTRODUCTION The grid-like structure is used to organize the elements according to their properties. The rows and columns tell specific information about the elements as does each box that represents an element.

INTRODUCTION We will take a brief look at the history and development of the table, and then examine the element cells, the structure of the table, and the reasons why the table is a useful tool for chemists and other scientists.

INTRODUCTION Before written history, people were aware of some of the elements in the periodic table. The first pure elements had been known since the time of the Ancient Greeks, who used the metallic elements such as gold (Au), silver (Ag), copper (Cu), lead, (Pb), tin (Sn), and mercury (Hg).

INTRODUCTION Between 1649 and 1869, the amount of knowledge about properties of elements and their compounds was added to by many scientists and chemists.

INTRODUCTION Hennig Brand, a German scientist, who discovered phosphorus (P) in French chemist, Antoine Lavoisier who in 1739 drew a table that contained 33 known elements at that time. In 1863 John Newlands, an English chemist, wrote a paper which organized the 53 known elements into 11 categories. German chemist Lothar Meyer who produced a periodic table in 1869.

INTRODUCTION By 1869, 63 elements had been discovered. A Russian scientist, Dmitri Mendeleev discovered a set of patterns that applied to all the elements.

INTRODUCTION Mendeleev knew that some elements have similar chemical and physical properties. Mendeleev thought that these properties were clues to a hidden pattern. He noticed that when he arranged the elements according to their atomic mass the properties of the elements repeated.

INTRODUCTION By arranging his cards into groups where all the elements shared properties, he noticed that there were blank spaces in the table. He predicted that the unknown elements that fit those spaces had yet to be discovered.

INTRODUCTION Mendeleev was correct.

INTRODUCTION Mendeleev is considered to be the father of the periodic table.

INTRODUCTION In 1913 Henry Moseley found a way to measure the positive charge of an atom, the atomic number, so the table was rearranged by atomic number, not mass As a result, some elements were shifted and the patterns of the table became even stronger.

INTRODUCTION Each element on the periodic table is represented by a chemical symbol. These symbols are shown along with other vital information in a cell on the periodic table.

INTRODUCTION 8 represents the atomic number. O represents chemical symbol represents atomic mass

INTRODUCTION The cells are arranged on the table in order of their atomic number. Each cell as you move from left to right increases by one proton, so hydrogen which is atomic number 1 has 1 proton, helium has 2 protons, lithium has 3 protons and so on.

INTRODUCTION The atomic number which represents the number of protons is also the number of electrons for each atom. In order for an atom to be stable, in other words it so it doesn’t just fall apart, the protons and electrons must balance each other.

INTRODUCTION The information from the table can also be used to help determine the number of neutrons in an element.

INTRODUCTION Once you know the atomic number of the element and its atomic mass you simply subtract to find the number of neutrons.

INTRODUCTION Let’s take the element aluminum which has a mass of 26.98, round that to a whole number, 27, then subtract its atomic number 13 from that. What did you get? If you got 14 then you are correct. Aluminum has 14 neutrons in its nucleus.

INTRODUCTION The names of the elements and their symbols also follow some rules. Element symbols are always 1, 2 or 3 letters. The first letter is always a capital, the 2 nd and 3 rd letter are always lower case.

INTRODUCTION You may have noticed that not all the elements have symbols that seem to match their names. Sometimes symbols are used that represent the Latin names. For example lead is Pb, which is Latin for Plumbum.

INTRODUCTION Many of the names of elements are given for the scientists who discovered them, some are named for cities, countries, or even gods.

OBJECTIVE Learn the rules for the rows and columns of the periodic table. Learn the rules for the cells of the periodic table.

IN ACTIVITY Use the periodic table in the back of your student agenda to find the chemical symbols for these elements. #14#2#10 #101#11#75 SiHeNe MdNaRe

VOCABULARY Periods – horizontal rows of the table. Groups – vertical columns of the table. Periodically – happening with regular occurrence.

NOTES Dmitri Mendeleev considered to be the father of the periodic table. Published his table in Arranged his table by atomic mass. Predicted the existence of unknown elements in his table.

NOTES Henry Moseley arranged the table according to atomic number in Some elements shifted because of this. The modern periodic table uses Moseley’s method of organization.

NOTES Each element has its own cell on the table. Most periodic tables include the symbol, the atomic number, and the atomic mass. Other info is sometimes added to the cells.

NOTES Atomic number – represents the number of protons and electrons in the atom. Chemical symbol Atomic mass – the average mass of the protons and neutrons in the nucleus of the atom.

NOTES Elements are named for cities, countries, famous scientists, or for Latin names. Symbols are always capitalized followed by lower case letters.

OUT QUESTION Calculate the neutrons for these elements. 1. Atomic number 22, atomic mass Atomic number 48, atomic mass

PERIODIC TABLE II

INTRODUCTION The properties of an element can be predicted from its placement on the periodic table. This predictability is the reason that the table is so useful to chemists.

INTRODUCTION The table is organized in horizontal rows called periods. A period contains a series of elements just as a week on a calendar contains a series of different days.

NOTES There are a total of 7 rows.

INTRODUCTION From left to right across the rows the properties of the elements change in a pattern. Elements on the left side of the table are highly reactive metals. Less reactive metals are in the middle of the table. Next comes the metalloids followed by the nonmetals.

INTRODUCTION The trends of reactivity are shown on the next slide. Elements are more reactive to the right side, less reactive in the middle and more reactive when you get to the halogens. Reactivity is greater at the bottom of the columns for metals and at the top of the columns for nonmetals.

NOTES Reactivity Increases Reactivity Decreases Reactivity Increases

INTRODUCTION Each of the elements in a row have the same number of energy shells that the electrons are located in. Those in the first row have one shell, the second row elements have 2 shells, the third row has three and so on up to the seventh row.

EXAMPLE

INTRODUCTION As a result of the repeating pattern of properties, the elements of the periodic table fall into 18 vertical columns, or groups.

EXAMPLE IA IIA IIIAIVAVA VIA VIIA VIIIA IBIIBIIIB IVB VBVIBVIIBVIIIBIXBXB

INTRODUCTION These groups, sometimes known as families, consist of elements with similar characteristics. For example, the elements in group 1 are metals that react violently with water, while the members of group 2 react with water slowly or not at all.

INTRODUCTION Other groups also have characteristics that are shared within their group. For example, group 17 elements react violently with elements from group 1 but group 18 elements rarely react at all.

INTRODUCTION All members of a vertical column also have another characteristic that is shared. If you look at all the members of group 1A they have one electron in their outermost shell. This pattern holds true for columns marked with an A but not for elements marked with a B.

Hydrogen - H Lithium - Li Sodium - Na EXAMPLE

IA IIA IIIAIVAVA VIA VIIA VIIIA IBIIBIIIB IVB VBVIBVIIBVIIIBIXBXB

INTRODUCTION Table is also color coded. There are 8 different color coded groups.  alkali metalsalkaline earth metals  transition metalsother metals  metalloidsnon metals  halogensnoble gases All members of a group share similar characteristics.

EXAMPLE

SPECIAL NOTE The two rows at the bottom, the Lanthanides and the Actinides are set out away from the rest of the table for convenience. They did this so the table would not be so long. There is usually a line showing where they would fit into the table.

EXAMPLE IA IIA IIIAIVAVA VIA VIIA VIIIA IBIIBIIIB IVB VBVIBVIIBVIIIBIXBXB

SPECIAL NOTE The elements on the table are not all solids, some are liquids and some are gases at room temperature. The chemical symbols are shown in different colors to designate which state they exist in at room temperature. Look for a special key on the table that tells you what state they are in.

SPECIAL NOTE The last special note is for a zig zag line that runs through the table. The line separates the table into the left side elements, which are all metals, and the right side elements which are all nonmetals.

IN QUESTION Which scientist was famous for discovering the proton? What was the experiment called that he was conducting when he made his discovery? Earnest Rutherford, the gold foil experiment

VOCABULARY Valence electrons – electrons in the outermost shell of an atom.

NOTES Table organized into rows, and columns. Rows are called periods Columns are called groups. Table is also color coded for elements that share similar characteristics.

ROW NOTES 7 rows (periods) in the table All elements in a row have same number of energy shells. (orbitals) Elements change reactivity moving from left to right.

REACTIVITY NOTES Most reactive elements on the left. Less reactive elements in the middle. More reactive elements in halogens. Less reactive elements in noble gases. Most reactive elements are at the bottom of columns for metals. Most reactive elements are at the top of columns for non metals.

COLUMN NOTES 18 columns (groups) in the table All elements in A columns have same # of electrons in valence shell (outermost shell) Elements in B columns do not follow the pattern.

NOTES Table is color coded for groups of similar characteristics. Zig Zag line separates table into metals to the left of the line, and nonmetals to the right.

NOTES Lanthanides and actinides are set out of the table for convenience. Not all elements are solids, some are liquids, some are gases.

OUT QUESTION You have an atom that has no electric charge. It has 5 protons and 6 neutrons. How many electrons will it have? What is the element? Explain. It will have 5 electrons to balance the charge. The element is boron.