History of the Periodic Table

Light and Heavy Elements

Antione Lavoiser

• showed up and discussed the law of conservation of mass

• did the first organizational work on the elements and came up with something called the 33 simple substances

• did have a lot of elements that he sorted, listed and he was starting to put them in columns of things that were combustible, metallic, compounds, and light elements

Johann Wolfgang Döbereiner

• come up with something called the model of triads

• notice patterns and reactivity amongst some of the elements

• Let us say lithium, sodium, and potassium are all group 1 elements and we take for granted that they react with all at the same stuff, but he found that they all reacted with water at room temperature and they all reacted with chlorine in a one-to-one ratio same with hydrogen, hydroxide

• found patterns and physical properties such that if you took the average of the lightest element in the triad and the heaviest, you would get the approximate mass of the middle element

Dmitri Mendeleev

• known as the father of the periodic table.

• worked on a lesson to understand the properties of matter and so he was putting the properties of each element on a note card and noticed that there were many similarities

• kept on repeating that observation that led him to systematically make a grid grouping of all the different elements and it was really the first periodic table format of sorts not just a list of the elements now

. How did Dmitri Mendeleev group the elements?

• Well, he borrowed some ideas from the scientist who came before him

  
  

• One scientist said element should be grouped together according to increase in its atomic mass he liked that idea, so he wound up doing that but in columns

Ernest Rutherford

• the guy who did the experiments that found relationship of creating atomic number and the number of protons in an element

• found that information by arranging the elements by increasing atomic number which prior to this believe it or not atomic number was just an arbitrary number that was given to the elements in succession on Mendeleev's periodic table.

• to summarize, our modern periodic table is arranged vertically in columns by similar chemical properties but now horizontally by increasing atomic number

• The periodic table has elements that are made up of metals non-metals and metalloids the first thing that should jump out at you about our metals is that they make up approximately two-thirds of our elements and the majority of all the elements on the periodic table are metallic.

• It's important to know the properties of metals many of them you probably remember from other classes but the notable ones are that they are generally shiny and hard they're great conductors of heat and electricity they're ductile which might be a new word for you which simply means you can stretch them into really thin wires.

• They are malleable which means they can be pounded into sheets without falling apart.

• All our metals are solid except for mercury which is liquid at room temperature.

• Mercury has a density of 13.5 grams per milliliter meaning that one milliliter of mercury would weigh thirteen and a half grams.