2 Demetri MendeleevBy 1860 about 60 elements were known and a method was needed for organization. In 1869, Russian chemist Dimitri Mendeleev proposed arranging elements by atomic weights and properties.The table contained gaps but Mendeleev predicted the discovery of new elements.
4 Important Features Atomic Number Symbol Name Atomic Mass We’ll learn more about these later…
5 What is the ATOMIC NUMBER? The number of protons found in the nucleus of an atomOrThe number of electrons surrounding the nucleus of an atom.
6 What is the SYMBOL?An abbreviation of the element name.
7 What is the ATOMIC WEIGHT? The number of protons and neutrons in the nucleus of an atom.
8 How do I find the number of protons, electrons, and neutrons in an element using the periodic table? # of PROTONS = ATOMIC NUMBER# of ELECTRONS = ATOMIC NUMBER# of NEUTRONS = ATOMIC _ ATOMICWEIGHT NUMBER
10 Elements share traits by FAMILIES (GROUPS) and PERIODS
11 The Elements are Separated into 9 Different Families on the Periodic Table 1. Alkali Metals2. Alkaline Earth Metals3. Transition Metals4. Rare Earth Metals5. Halogens6. Noble Gases7. Metalloids8. Non-Metals9. Other Metals
12 FAMILIES : Alkali Metals Very reactive metals that do not occur freely in natureOften found in saltsMalleable, ductile, good conductors of heat and electricity.Can explode if they are exposed to water
13 FAMILIES : Alkaline Earth Metals Very reactiveNot found free in nature
14 FAMILIES : Transition Metals Ductile And malleable, and conduct electricity and heatIron, cobalt, and nickel, are the only elements known to produce a magnetic field
18 Metalloids have Properties of both metals and non-metals Some of the metalloids are semi- conductors. This means that they can carry an electrical charge under special conditions. This property makes metalloids useful in computers and calculators (“Silicon Valley”)
19 Non-Metals Not able to conduct electricity or heat very well Very brittleDo not reflect light
20 Other Metals Ductile and Malleable Many are man-made Solid with a relatively high densityOpaque
21 Metals Non-Metals Metalloids To Summarize: They are solid (except Mercury)They are shiny, good conductors of electricity and heat.They are ductile and malleableMetalsBrittle (not malleable or ductile)Poor conductors of both heat and electricityNon-MetalsContain properties of both metals and non-metalsMetalloids