Transition Metals By Daijon Rice, Jamie Elie, Kita Hebron, Lauren Larsen & Mekedes Mekonnen.
Background Information Transitional elements are located in groups 3-12 on the periodic table (the d-block). The 38 elements were discovered between the years of 1879 (Scandium) and 1996 (Unuoblum) The interesting thing about transition metals is that their valence electrons, that are used to combine with other elements are present in more than one shell. The name transition comes from their position in the table — they form a transition between the main group elements, which occur in groups 1 and 2 on the left side, and groups 13 – 18 on the right.
Physical Properties of Transition Metals High Melting Points High Density High Boiling Points High electrical conductivity (due to it’s loosely bound electrons)
Physical Properties continued Malleable and ductile (they can be hammered and coiled) Metallic Luster (shiny & polished surface) Generally insoluble High tensile strength Hard/firm (solid form)
Physical Properties Continued Most transition metal compounds are highly colored, the color of transition metals arises from a split in the energies of the d orbital's caused by coordinated molecules. One property of transition metals is the formation of highly colored ions in solution, which leads us to our chemical properties. . . .
Learning Check (site Dr. Wilson What is the only transitional element that is liquid at room temperature ?
Answer Hg !!
Chemical Properties of Transition Metals Forming of coloured compounds Forming compounds with variable oxidation states A strong tendency to form complexes . Useful as catalysts
Chemical Properties Continued Transition elements provide a wide range of oxidation states or positively charged forms because they have high electrical conductivity and they are very malleable.
Chemical Properties Continued Transition metals have a tendency to form complexes (coordination compounds) this is due to their partially filled d sub-shell accepting donated electron pairs from other ions or molecules. A complex ion is an ion containing a central atom or ion to which other atoms, ions or molecules are bonded. The atoms, ions or molecules are bonded to it with dative covalent bonds.
Chemical Properties Continued A catalyst is a substance that speeds up a chemical reaction, but is not consumed by the reaction; hence a catalyst can be recovered chemically unchanged at the end of the reaction it has been used to speed up, or catalyze. Transition metals and their compounds function as catalysts either because of their ability to change oxidation state or, in the case of the metals, to adsorb other substances on to their surface and activate them in the process . Example: Formation of ammonia from nitrogen and hydrogen using iron as the catalyst. Fe N2(g) + 3H2(g)--->2NH3(g)
Learning Check (sited Dr. Wilson) What is catalyst ?
Answer A catalyst is a substance that speeds up a chemical reaction, but is not consumed by the reaction.
Atomic Trends of Transition Metals The transition metals, groups 3 – 12 in the periodic table, are generally characterized by partially filled d sub-shells in the free elements or their cations. Unlike the s -block and p -block elements, the transition metals exhibit significant horizontal similarities in chemistry in addition to their vertical similarities.
Atomic Trends The main periodic trends include: Electron Configuration electronegativity ionization energy atomic radius melting point metallic character
Atomic Trends Continued Cr (chromium) and Cu (copper) are to exception as to how the d-orbitals are filled. See example on the board.
Atomic Trends Continued Transition metals have high melting/boiling points due to strong metallic bonds. Therefore, the more unpaired electrons are present, the higher the melting/boiling point will be, the first 4 elements in a row always have the highest points, as the unpaired d orbital electrons pair up, it decreases. The last 5 elements in a row have a lower melting/boiling points.
Atomic Trends Continued Ionization energy is how much energy is required to move one electron from an element to the outer shell. Ionization energy increases from left to right and from bottom to top due to the number of valence electrons increasing from left to right on periodic table.
Atomic Trends Continued The atomic radius decreases from left to right due to protons being added to the nucleus. The concentration of more protons in the nucleus creates a " higher effective nuclear charge ." In other words, there is a stronger force of attraction pulling the electrons closer to the nucleus resulting in a smaller atomic radius. The atomic radius increases from top to bottom due to the increase of electrons.
Atomic Trends Continued Metallic characteristics decrease from left to right across a period, this is caused by the decrease in radius. Metallic characteristics increase down a group, due to electron shielding which causes the atomic radius to increase thus the outer electrons ionizes more readily than electrons in smaller atoms.
Atomic Trends Continued Electronegativity is the ability of an atom to pull electrons to itself and increases from left to right and bottom to top . If electrons are being shared equally between atoms, the bonds will be polar, if not they will be non-polar.
Learning Check (site Dr. Wilson) What is Electronegativity ?
Answer Electronegativity is the ability of an atom to pull electrons to itself.
Transition Metals in Nature Gold, silver & copper are 3 examples of transition metals which occur in nature in a metallic state. (to the side is an example of gold (top), copper (bottom) in nature form)
Transition Metals in Industry Gold, silver & copper are also used in industry. An example is over on the side, copper, silver, gold; respectively.
Copper Some other industry uses of copper: electrical wiring, build infrastructure, homes, factories, office buildings, ships, wind turbines, trains, jets and automobiles. Copper and copper-based products are also used in appliances, decorative brassware, locks and keys.
Gold Industry uses for gold: Monetary, jewelry, art, gold has many practical uses in dentistry & electronics, including electric wiring & colored- glass production.
TUNGSTEN – W Can you recall hearing of this transition metal before ? Most likely not, however it is a big part of something which we all enjoy everyday.
Tungsten Continued Tungsten , also known as wolfram , is a chemical element with symbol W and atomic number 74. The word tungsten comes from the Swedish language tung sten directly translatable to heavy stone. W has melting point of 3,422 degree C. Tungsten has the highest melting point of all the elements, making it ideal for use in a light bulb.
Tungsten Continued Halogen light bulbs are a newer improved, more efficient/green light source, by adding the element Tungsten the product of the light blub was enhanced. The light is produced by a piece of tungsten metal or filament, which shines brightly when an electrical current is passed through it. This process is called incandescence and is due to electrons becoming excited and moving through the tungsten, releasing energy as heat and light.
Tungsten Continued Further benefits of the halogen light bulb: reduces eye strain (due to the bright light), illuminates details, longer lifespan (last significantly longer than standard light bulbs & produces more light per watt of usage.
Tungsten Continued When Tungsten and carbon react at high temperature makes a very hard gray compound known as Tungsten Carbide. Tungsten Carbide is a very hard metal with a melting point of 2, 8700 degree Celsius. It is used for wide verity of things and one of them is to make cutting and drilling tools The following You Tube video shows how strong tungsten carbide is compared to other metals.
http://www.youtube.com/watch?v=K1P8Lp zFbh8&feature=youtu.be
In Conclusion Sources used: Google images www.googleimages.com Periodic Table: Transition Metals http://www.chemicalelements.com/groups/transition.html ChemWiki http://chemwiki.ucdavis.edu/Inorganic_Chemistry/Organ ometallic_Chemistry/Structural_Fundamentals/Periodic_ Trends_of_the_Transition_Metals How Stuff Works: Tungsten http://home.howstuffworks.com/light-bulb2.htm
Recommend
More recommend
