PROPERTIES OF NON-METALS
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cover image - https://www.slideshare.net/KunalGupta146/physical-properties-of-metals-and-non-metals
top insulators image - https://www.slideshare.net/ms_yam/y8-electricity-04-resistance
bottom insulators image - http://class312015.westthorntonblogs.net/2016/05/02/electricity-conductors-and-insulators/
top brittle image - https://www.goalfinder.com/product.asp?productid=72
bottom brittle image - http://www.liacoseducationalmedia.com/shedding-light-on-atoms-episode-4-the-periodic-table
dull image - http://science.taskermilward.org.uk/mod1/Year%208/Mod9/Mod9_4.htm