The Periodic Table – explained



The Periodic Table – explainedThe periodic table is based on the physical and chemical properties of elementsRecall: An element is a pure substance that is made up of one type of particle, or atom. Each element has its own distinct properties and cannot be broken down into simpler substance (by means of a chemical change)In the 1860’s, Dmitri Mendeleev made cards for each known element and recorded all known information and properties of that element. *note: the first chemist to report a new element has the right to name it. ie: Element #99 “Einsteinium”Mendeleev then pinned the cards up arranging them by atomic numberIn doing this he noticed repetitive patterns which… … Spurred the modern periodic law:If the elements are arranged according to their atomic number, a pattern can be seen in which similar properties occur regularlyIn addition, he noticed that:As atomic numbers increase, so do atomic massThe atomic number is almost half the atomic massThe vertical columns share similarities (they are called groups / chemical families)Horizontal row share similarities (they are called periods)Metals are at the left of the tableNon-metals are on the rightSmaller atoms are at the top, where as larger atoms at the bottomLet’s take a closer look at the groups in the periodic table1. Metals- Shiny appearance & luster- Solids at room temperature (except Mercury; Hg)- Conduct electricity and heat- Malleable (can be hammered into sheets)- Ductile (can be stretched into wires)- Most elements are metals- Copper, Aluminum, Gold, Lead, Tin, Calcium, Sodium, etc.2. Nonmetals- Solid, Liquid (Bromine), or Gas at room temperature- Solids are brittle and dull- Solids cannot be stretched into wires- Poor conductors or electricity and heat- Oxygen, Hydrogen, Sulfur, Carbon, Helium, Chlorine, etc.3. Metalloids- “In between” metals and non-metals- Have properties of both- Silicon, Boron, etc._______________________________________________________________________________________________Now, let’s take a closer look at our Metals !! Group 1: Alkali MetalsVery reactive—larger atoms in group are MORE reactiveHave 1 valence electron – need to LOSE 1 to have a stable octetExample: Na reacts when exposed to waterGroup 2: Alkaline Earth MetalsVery reactive however, less that the Alkali MetalsLarger atoms are more reactiveHave 2 valence electrons – need to LOSE 2 electrons to have a stable octetGroup 7: HalogensVery reactive—smaller atoms in group are more reactiveHave 7 valence electrons- need to GAIN 1 more to have a stable octetFluorine is almost never found in pure elemental form because it is so reactiveUses: Chlorine in pools, Iodine to disinfectGroup 8: Noble GasesVery unreactiveHave 8 valence electrons * this is called a stable Octet = a filled valence shell (octo = 8) means the atom is chemically stableFound in nature mostly as gasesUses: Argon in light bulbs, Neon lights, Helium fills balloons, etc. GROUPS OF ELEMENTSGROUP NAMEEXAMPLESCHARACTERISTICS Alkali MetalsAlkaline Earth MetalsHalogensNoble GasesNotes: __________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ ................
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