Presentation on theme: "The Periodic Table. What is PERIODIC? Meaning they had a regular, repeating pattern As a table take the deck of cards and come up with as many ways the."— Presentation transcript:
What is PERIODIC? Meaning they had a regular, repeating pattern As a table take the deck of cards and come up with as many ways the deck of cards could be laid out so that the cards form some sort of identifiable pattern. Write out all the different patterns as you can in your notes.
The periodic table is the most useful tool to a chemist. You get to use it on every test. It organizes lots of information about all the known elements. Why is the Periodic Table important?
Pre-Periodic Table Chemistry … …was a mess!!! No organization of elements. Imagine going to a grocery store with no organization!! Difficult to find information. Chemistry didn’t make sense.
Arranging The Elements Who came up with the idea of the Periodic Table of Elements? A Russian chemist named Dimitri Mendeleev. He wrote the properties of the elements including density, appearance, atomic mass, melting point, etc on pieces of paper then classified them according to similarities.
Mendeleev’s Periodic Table HOW HIS WORKED… Put elements in rows by increasing atomic weight. Put elements in columns by the way they reacted. SOME PROBLEMS… He left blank spaces for what he said were undiscovered elements. (Turned out he was right!) He broke the pattern of increasing atomic weight to keep similar reacting elements together.
Examples of periodic Mondays occur once every 7 days The good news is…so do Fridays! Leap year occurs once every four years The sun rises each day and sets each night Your birthday occurs once per year
The elements are periodic Mendeleev saw that the elements had a regular repeating pattern When he arranged them in order according to increasing atomic mass, similar chemical and physical properties were observed in every eighth element…a periodic repetition!
Predicting Missing Elements In Mendeleev’s day, there were only 60 elements that had been discovered so, as Mendeleev organized the table, he noticed that there were some elements missing and boldly predicted that there were some elements yet to be discovered.
Predicting Missing Elements Mendeleev also predicted the properties of the missing elements by using the pattern of properties In the periodic table. Incredibly, a few years later, gallium was discovered and its’ properties matched Mendeleev’s predictions very well. Since that time, all of the missing element’s on Mendeleev’s periodic table have been discovered!
Changing the Arrangement Mendeleev noticed that a few elements in the table that were not in their correct place according to their properties. Incorrect atomic mass perhaps? In 1914, a 26 year old British scientist named Henry Moseley solved the mystery.
Henry Moseley Figured out the number of protons – the atomic number – in an atom. He rearranged the elements by atomic number and every element fell into it’s proper place in the improved periodic table.
Periodic Law More elements have been discovered since then and each have supported the periodic law. The periodic law states that the chemical and physical properties of elements are periodic functions of their atomic numbers
Chemical Symbol Each square on the periodic table contains information about an element including its atomic number, atomic mass, name, and chemical symbol. The chemical symbol for each element usually consists of one or two letters. The first letter is always capitalized and the second letter, if there is one, is in lower case
Periods Each horizontal row of elements is called a period They are called a called a period because they follow a repeating, or periodic, pattern as you move from left to right The physical and chemical properties of elements such as conductivity and the number of electrons in the outer level of atoms change gradually from those of a metal to those in a nonmetal
Groups Each column of elements from top to bottom is called a group. Elements in the same groups often have the same chemical and physical properties. Sometimes a group is also called a family
Metalloids Found on both sides of the zigzag line Properties –semiconductors of thermal energy –Might be malleable or might be malleable –Some are shiny; some are dull –Some are ductile; some are not