Metallic Bonding What are Metals? A metal is an element that readily forms positive ions (cations) and has metallic bonds. What are Metals? On the periodic table, a diagonal or stair step line drawn from boron (B) to polonium (Po) separates the
metals from the nonmetals. Elements on this line are metalloids, sometimes called semi-metals; elements to the lower left are metals; elements to the upper right are nonmetals. Almost 80% of the elements on the periodic table are metals. Metallic Bonds The valence electrons of metal atoms can
drift freely from one part of the metal to another- this is sometimes called a sea of electrons Metallic bonds consist of the attraction between these free floating electrons and the positively charged metal ions (cations). This attraction is the bond that holds metals together.
Physical Properties of Metals Lusterous- they are shiny! High density- atoms are tightly packed. Good conductors of electricity and heat. Reason- electrons can flow freely. Physical Properties of Metals Ductile- they can be drawn into wires AND
Malleable- they can be hammered into shapes Reason- cations can slide easily past each other because the sea of electrons insulates them and prevents strong repulsions. on the other hand Ionic compounds are brittle and break
easily? Why Physical Properties of Metals Metal ions are arranged in very compact orderly patterns. Similar to the way apples are stacked at the grocery store. Pure metals form the simplest kinds of crystals
Chemical Properties of Metals Most metals are chemically unstable and will react will oxygen in the air- that is they form oxides- over varying timescales (for example iron rusts over years and potassium burns in seconds).
Chemical Properties of Metals -The alkali metals react quickest followed by the alkaline earth metals. -The transition metals take much longer to oxidize (such as iron, copper, zinc, nickel). Others, like palladium, platinum and gold, do not react with the atmosphere at all. -Some metals form a barrier layer of oxide on their surface which cannot be penetrated by further oxygen molecules and thus retain their shiny
appearance and good conductivity for many decades (like aluminium, some steels, and titanium). Alloys Very few metals that you encounter daily are pure metals. Most metals are alloys, a mixture of two or more elements of which at least one is a metal.
Examples: Brass is an alloy of copper and zinc Sterling silver is an alloy of silver (92%) and copper (8%) Stainless Steel is an alloy of iron (81%), chromium (18%), nickel (1%), and trace amounts of carbon. Alloys are important because their properties are often superior to those of their component elements.
Examples: Sterling silver is harder and more durable than pure silver, but still soft enough to make jewelry and tableware. Brass is harder and easier to shape than either copper or zinc
Richmond Summer Youth Employment Program Highlights Challenges #1 ranking in California as the most violent city (per capita) #9 in the country (City Crime Rankings) 50%-60% High School Drop Out Rate 49%-56% of students pass the High School Exit Exam...
Administrative Simplification. Identify areas of improvement through provider/member complaint logs and patient, provider, health plan, and advocate insights then simplify processes to reduce administration cost burden through process improvement
Overview. Titration is an analytical method which is widely used in many different segments and for many different samples. Chemical industry: Water content in solvents, acid value in resins and polymers, hydroxyl value in polyols, surfactant content in raw materials,...
LS = Topographic factor, L = Slope length factor: ratio of loss from a given slope length to soil loss from a 72.6 ft length under the same conditions. S = Slope steepness factor: ratio of loss from a 9%...
3a. Medical Treatment: Long-acting Non-selective 1-blockers Dosage is increased in a stepwise fashion at weekly intervals. Does not affect PSA. Acts to relax prostatic/bladder neck smooth muscle (& vascular smooth muscle - non selective)