Atoms and Elements

Elements

There are roughly about 100 elements. An element is a substance that cant be split into anything simpler by chemical reactions. A molecule is the smallest part of a chemical compound and the smallest part of an element that can exist in nature. A mixture is where two or more substances have been mixed not joined toghether. A compound is a substance made from the atoms of two or more different elements joined toghether.

The difference between a physical and chemical change is that a physical change is tempary and a chemical change is permanent.

The periodic table is a chart to show the elements group, name and symbol

The metals are found from aluminum stairs down.

Newlands put all the elements that they knew of in 1864 down in lightest to heaviest. Once he did this he found a pattern. Which was every 7 the 1st elelment and the 7th element would have similar properties, but there was a problem with this and that was that it only worked for the first 20. Madaleev basically said that Newlands was wrong. So after that he used Newlands 

theory but instead of putting them in weight order he picked out ones that had similar properties and put them in columns. Where he didnt know the element he left a gap. Eventually he was left with a table with quite a few gaps in so he tried to predict what they were. Only three of the elements he predicted were right but thats pretty impressive. One thing that mandaleev did was miss out a whole group. The 4 noble gases. This group was found by a Scot called William Ramsay. Eventually Henry Moseley worked out that the table shouldnt be done by mass it shpuld be done by what they were made put of as argon is hevier than pottasium but argon is in the group before potassium?