Please enable JavaScript.
Coggle requires JavaScript to display documents.
B5 U1 - Coggle Diagram
B5 U1
Journey of discovering the Atom !
Daltons: All matter is composed of small particles called as "Atomos".
Limitations, Cons
Why and How atoms combine to form compounds
Allotropes
With the discovery of positively and negatively charged subatomic particles, they couldn't be considered invisible
Pros
The theory could explain the theory of conservation of mass
First brought up the concept of atoms
Postulate
He said all elements are made up of tiny, invisible particles called atoms.
,
atoms can neither be created nor destroyed during chemical reactions
Atomos of the same elements are identical, but atomos of different elements would not be identical
Joseph John Thomson: Discovery of positively and negatively charged particles using a cathode ray tube; The plum pudding model
Postulate
Atoms can be divided into smaller subatomic particles that consist of negatively and positively charged particles
Atoms are comosed of electrons scattered throughout a spherical cloud of positive charge
Pros
Recognized electrons as components of atoms
Discovered atoms are electrically neutral
No net electrical charge, the charge from a protons or electron are of equal strength
Limitations, Cons
There was no mention of the nucleus which was further discovered in Neil Bors Gold foil experiment
Never told if electrons had a fixed arrangement inside of the atoms
JJ Thomson was not able to explain how the positive charge held the electrons inside of the atom
Cathode ray tube experiment
Cathode ray tubes are sealed glass tubes where most of the air has been removed. A high voltage is applied across two electrodes at one end of the tube, which causes a beam of particles to flow from the cathode to the anode.
Cathode ( negativley charged electrode)
Abode (positively charged electrode)
The test the proprieties of the particles, Thomson placed two oppositely-charged plates around the cathode ray. The cathode ray was deflected away from the negatively charged electric plate and towards the positively-charged plate.
The cathode ray bend towards the positively charged electrode when passing between the charged metal electrodes.
JJ thomson experimented on the different metals of the electrode material
The properties of the cathode ray stayed the same
Neil Bor's: The position of positive subatomic particles and electrons; the idea of energy orbitals
Postulate
Ernest Rutherford: The introduction of the position of positive subatomic particles
Limitations
electron accelerating around the nucleus would continuously emit electromagnetic radiation and lose energy
Bonding
ionic vs covalent compounds
Low melting/boiling point
High melting/Boiling point
Hard/Brittle
Good insulators
Conductors in a molten or aqueous state
Form crystal
Soft/flexible
More flammable
Not usually soluble in water
Do not conduct electricity when dissolved
Covalent bonding
A covalent bond in when two nonmetals share their valance electrons in order to gain chemical stability
Simple molecules contain a few atoms held together by strong covalent bonds
Ex: Carbon dioxide (CO2)
Poly atomic Ions