Unit 2 Notes 1 Flashcards
Believed matter consisted of elements
- earth
- air
- fire
- water
Alchemy (13th - 18th centuries)
Even though alchemists did not know about or discorer any parts parts of the atom they are a very important group of people
What was their main goal?
Turning Lead into gold and finding the elixir of life
John Dalton -Early 1800s
- proposed the idea the atom was the smallest particle of matter
- English school teacher
- the atom was an indivisible sphere with uniform density
-atoms of the same element had the same mass and properties - COULD NOT EXPLAIN BONDING
- known as the Billiard ball model
Sir William Crookes (1890s)
- theorized the existence of electrons
- cathode ray tube experiments
J.J. Thomson
- 1903 proved the existence of +ve particles known as protons and believed atoms consisted of electrons (-ve) and protons (+ve)
-he thought the protons gave the atom mass while the elections held the atom together - 1897 refined cathode ray tube and proved the electron existed.
- known as the Plum Pudding model
Becquerel (1896)
- accidentally discovered radioactivity
Rutherford (1911)
-discovered the protons were in the center of the atom called the nucleus
-electrons rotated around the center
- most of the mass was located in the nucleus
- known as the Planetary Model
James Chadwick (1932)
-discovered the neutron
-believed the neutron was in the nucleus and provided mass to
the atom
- known as the modified planetary model
Scientists knew early on that they needed to organize their world
ie the elements and other scientific data. As a result a number ot periodic tables” were developed. However it wasn’t until the 186.05 that a useful periodic table was created
Dmitri Mendeleev
- a Russian scientist developed the figst useful periodic table
-he organized the table by chemical properties and increasing atomic mass - his table had blank spaces unlike the table of to day
- known as the “Father of the Periodic Table”
Why did Mendeleev leave spaces throughout his table?
There were elements that weren’t discovered yet. He used his periodic table to predict the properties of these missing elements.
The Periodic Law
The properties of the elements occur periodically when the elements are arranged in increasing order by their atomic numbers.
Periodic Table can be divided into rows in columns
There are 4 rows on the Periodic Table known as series or periods.
There are 18 columns on the periodic table known as groups or families
Group 1- The Alkali metals
-very reactive.
- become more reactive and metallic down the group
- 1 valence electron -electron in the outer shell
- Li, Ne, K, Rb, Cs, Fr
Group 2- Alkaline Earth Metals
-reactive metals
- more reactive and metallic down the group
- 2 valence electrons
- Be, Mg, Ca, Sr, Ba, Ra
