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Dmitri Mendeleév (1834-1907) The Periodic Table of the Elements is based on the work of Dimitri Mendeleév, a Russian professor of chemistry. It is a key tool for Chemists. It helps us to organise the chemical elements by placing elements with similar properties next to each other – this allows us to study trends and patterns in the behaviour of the chemical elements. At first glance it has a peculiar shape, but further studies reveal the beauty and order in its design. 23/02/2019 nrt

Mendeleév’s predictions were as follows... In Mendeleév’s day only 60 elements had been identified, but he organised the table on the basis of the physical and chemical properties of the elements. He guessed that some elements were missing and left gaps for them. In 1869 he published his version of the Periodic Table and used it to predict the properties of some of the missing elements, e.g. one undiscovered element was in the position indicated by the red square. Mendeleév’s predictions were as follows... 23/02/2019 nrt

Mendeleév’s Predictions Germanium (Ge) was discovered in 1886. (17 years after Mendeleév made his predictions) His predictions were shown to be remarkably accurate. Mendeleév’s Predictions Observed Properties Will be a light grey metal Germanium is a greyish white metal One atom of Germanium combines with two atoms of oxygen (white powder), and has a melting point above 1,000º C Will form a white dioxide (powder) which has a high melting point The oxide will have a specific gravity of 4.7 Germanium oxide has a specific gravity of 4.703 The chloride will have a boiling point below 100º C Germanium chloride boils at 86.5º C The chloride will have a specific gravity of 1.9 Germanium chloride has a specific gravity of 1.887 23/02/2019 nrt

A horizontal row of the periodic table is called a period. The blue period is called the first short period. The red period is called the first long period. 23/02/2019 nrt

The vertical columns of the periodic table are called groups. II III IV V VI VII GROUP The vertical columns of the periodic table are called groups. The blue group is called Group I (1). The red group is called Group 0. Other groups are numbered II to VII (2 to 7). 23/02/2019 nrt

I II III IV V VI VII Inert Gases Alkali metals Alkali Earth metals Alkali Metals Alkali Earth Metals Halogens Inert Gases Halogens All of the eight groups have specific names. Four important groups are also known as families of elements:- All member elements of a group have similar chemical and physical properties. 23/02/2019 nrt

Atomic number increases both across and down the table. II III IV V VI VII 1 2 3 4 5 6 7 8 9 10 11 18 19 36 37 54 55 56 72 86 87 88 104 57 58 71 89 92 103 The elements are arranged in order of their atomic numbers. Some important ones are... Atomic number increases both across and down the table. Period lengths differ because of the varying electronic structures of the elements. 23/02/2019 nrt

I II III IV V VI VII Transition Metals Rare Earth Metals Transition Metals Lanthanides Rare Earth Elements Actinides The central block of elements are know as the transition metals. Elements shown with a dotted line border are artificial. The Lanthanides are commonly known as the rare earth elements as they are rare and valuable. and Actinides 23/02/2019 nrt

Most of the elements (over 80) are metals. I II III IV V VI VII Metals Non-metals Metalloids Most of the elements (over 80) are metals. The other elements (22) are called non-metals. The metals and non-metals are separated by a ‘zig-zag’ border. Around the border are found elements which possess both metallic and non-metallic properties – called metalloids. 23/02/2019 nrt

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Group 1A contains the alkali metals. II III IV V VI VII Li Na K Rb Cs Fr Group 1A contains the alkali metals. They are all low density metals which react violently with cold water. 23/02/2019 nrt

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Group2A contains the alkali earth metals. II III IV V VI VII Be Mg Ca Sr Ba Ra Group2A contains the alkali earth metals. They all produce weakly alkaline solutions when dissolved in water. 23/02/2019 nrt They are commonly found in rock and salt deposits.

Calcium deposits in dead animal tissues lead to fossilization. Calcium is an important mineral for tooth and bone development. 23/02/2019 nrt

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Group 7 contains the halogens. They are non-metallic coloured elements with many similar chemical properties. 23/02/2019 nrt

Salts of the halogens, or halides, are commonly found in sea water. The salty deposits around this hot spring in Yellowstone National Park, Wyoming, U.S.A. contain fluorides, bromides, chlorides and iodides. 23/02/2019 nrt

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Group 0 contains the Noble (or inert) gases. They are all colourless gases which are almost totally unreactive with any other elements. 23/02/2019 nrt

Only in recent years have chemists found it possible to synthesize compounds of the Noble gases. Xenon, for example, will react with Fluorine at high temperatures. Fluorine is a highly reactive element. The diagram shows a space filling molecular model of the product, Xenon tetrafluoride XeF4. When this was achieved the name of the group of elements was changed from the inert gases to the Noble gases. 23/02/2019 nrt

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The block of elements highlighted here contains the transition metals. They are all shiny hard solids (except for one!) which usually produce brightly coloured chemical solutions. 23/02/2019 nrt

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The block of elements highlighted here contains the Rare Earth metals. This block contains some of the rarest elements on earth. The elements after Uranium are all synthetic elements, produced in high energy physical reactions. 23/02/2019 nrt

Probably the best known rare earth element is Uranium Probably the best known rare earth element is Uranium. It is used to make fuel rods for nuclear power stations. The photograph shows the reactor blocks at Trawsfynydd Nuclear Power Station in North Wales. 23/02/2019 nrt

In this diagram the chemical symbols of the elements are shown In this diagram the chemical symbols of the elements are shown. Each element has a unique symbol. These elements combine chemically to form the compounds of the universe. 23/02/2019 nrt