a history of chemistry
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A history of chemistry. “Old dead guys”. It all started back when…. 400 BC- Democritus- first to come up with the idea that things are made of “atoms”. Skip to. 1803- John Dalton Proposed the atomic theory. Next was. 1869- Dmitri Mendeleev - PowerPoint PPT PresentationTRANSCRIPT
400 BC- Democritus- first to come up with the idea that things are made of “atoms”
It all started back when…
1869- Dmitri Mendeleev Arranged elements into 7 groups with
similar properties… 1st version of periodic table.
Next was
Established that the nucleus of an atom was very dense and positively charged while electrons were outside the nucleus
1911 Rutherford
First of all… Elements are substances that cannot be broken down into simpler parts
Elements are made of atoms.. .Carbon is made of carbon atoms etc.
How small is an atom??? We can break down an atom but it loses its
properties when we do…
Moving on to atomic structure
Very tiny Mass is basically zero (m=0) Negative charge (-1) Located flying around the nucleus
Electrons
Very large compared to electrons (mass =1) Positive charge (+1) Located in the nucleus of an atom
Protons
If this were the size of hydrogen nucleus, the electron would be spinning about a quarter mile away….
In a neutral atom, protons always equal electrons
Hydrogen has… 1 proton… 1 electron Helium has… 2 protons… 2 electrons
Atomic number = number of protons in nucleus
Atomic Mass= how many protons AND neurtons
How many protons in H? How many neutron in H How many electrons?