Atomic Theory Flashcards
(31 cards)
Define an atom
The smallest particle of matter that still retains the properties of an element
Define an element
Structure only made up of one type of atom
Define an isotope
An atom with a different amount of neutrons but same amount of protons
Define a compound
Structure composed of two or more elements
Define an ion
An atom that has lost or gained an electron
Define a homogenous mixture
Composed of two or more substances and has the same composition and properties
Define a heterogeneous mixture
Composed of two or more stub stances and don’t have the same composition and properties
What is the mass number
The top number (neutrons plus protons)
What is the atomic number
The bottom number (amount of protons)
Who are part of the ancient views of atomic theory
- Thales
- Kanada
- Democritus
- Aristotle
What was Thales view on atomic theory
624BC
Water is the essence of all matter
What was Kanada’s view on atomic theory
600BC
Theorised the existence of 4 kinds of atoms which combined to make di/tri atomic molecules
Democritus’ view on atomic theory
430BC
Theorised the existence of invisible ‘atoms’ that had different sizes and shaped depending on the type of atom
Aristotle’s view on atomic theory
384 BC
Matter is made up off ‘ether’ of the 4 earthly elements and ‘nature abhors a vacuum’
What did Joseph Priestly do
1773, isolated O2 gas
What did Lavoisier do
Showed that 02 is used in combustion —> law of mass conservation
What is Dalton’s atomic theory
1) elements are made of small particles called atoms
2) atoms of one element are identical
3) atoms cant be sub divided, created, or destroyed
4) atoms do different elements combine at specific ratios
5) in chemical reactions- atoms are combines, separated or rearranged
Who discovered the electron
J.J Thompson 1897
RA Millikan 1909
How did JJ Thompson discover the electron
- using a cathode ray which produced a stream of particles that were independent of the material composition of the cathode.
- saw that they were negatively charged bc it went to the pos electrode
- calculated the ratio of charge to mass and saw it had to be sub atomic
How did RA Millikan discover the electron
- used oil drops to measure the charge of an electron
- drops fell at a constant rate between electric fields so the charge was discovered
What is JJ Thompsons atomic model
- plum pudding model
- nucleus wasn’t discovered
- each electron was paired with a positive particle so overall neutral charge in a cloud of positive charge
How was the proton discovered
1911
Part of rutherford’s experiment
Who discovered the nucleus
Rutherford 1911
How was the nucleus/ proton discovered
Gold foil experiment
- gold foil is 1-2 atoms thick and alpha particles were projected at it
- most went straight through but some deflected back
- alpha particles hit somethings, small, dense and positive
