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Chemistry

Atomic Structure

CHAPTER TWO

Rutherford’s Gold Foil Experiment

Ernst Rutherford conducted the Gold Foil experiment to prove the assumptions made by JJ Thompson and thereby propose a model for the structure of the Atom.

But the results were contrary to his expectations.

Apparatus:

 

atom

 

Uses of the various equipments in the apparatus:

Alpha Particles: These are dipositive Helium atoms, to be clear Helium atoms whose both the electrons have been snatched away, this makes it highly unstable and can cause you cancer by destroying your genetic matter.  You would not want it in your bookshelf, or would you?

Lead Box: The only substance dense enough yet cheap, that can stop α-particles from going helter-skelter. FYI: It’s poisonous, not to be consumed.

Gold Foil: Gold is the really heavy element and comparatively cheap and stable with respect to other heavy, solid metals. A heavy element is ideal as it has a bigger nucleus.

ZnS Screen: Zinc Sulphide is a phosphorescent material and creates sparks when it comes in contact with highly charged particles (here α-particles). It helps to observe the result of the experiment.

Charged Poles: Since the α-particles are positive the positively charged poles help to concentrate and fire the α-particles in a straight path by repelling it from every direction. (I suppose you get my point)

Assumptions

 

  • Rutherford based his idea on Thomson’s and had assumed that most of the α-particles would pass right through the foil without much disturbance.
  • The contents of an atom are evenly spread.

 

 

Observation and Results

 

  • Most of the α-particles went straight through the foil but a few of them did deflect and 1 in 12,000 completely reflected back, this implies that the contents of an atom is not evenly spread and,
  • The positive part of the atom is concentrated in the centre and there is a lot of empty space around it.
  • Thus the model was named as planetary model

 

 

220px-rutherford_atomic_planetary_model-svg
Rutherford’s Model Of Atom


Atomic Model of Bohr is available in detail in next chapter.


ARYAMAN

any doubt – feel free to ask in the comment box

suggestions can be provided in the comment section


FOR MORE KNOWLEDGE VIEW CHAPTER THREE OF ‘ATOMIC STRUCTURE’

 

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Atomic Structure

CHAPTER ONE

My favourite subject is chemistry. Especially atomic structure. So what is an Atom? Atoms are the basic (atoms are made up of subatomic particles.) unit of matter. And matter is something that has mass and occupies space. Atoms are made up of subatomic particles (and other tinier particles-which isn’t that important) which are grouped into two major parts:

  • The Nucleus- it contains Protons which are positively charged and Neutrons which are neutral in charge. (those extra particles are in here too.)
  • Shells- or orbits are the path in which the third major part, Electron which contains negative charge, revolve around the nucleus, like planets revolving around the Sun.
The Basic Structure Of an Atom
The Basic Structure Of an Atom

Think: IF THE NUCLEUS CONTAINS POSITIVE CHARGED PARTICLES ONLY WHY DON’T THEY REPEL (like charges repel)  AND WHY DOESN’T THE ATOM SPLIT (OR DISINTEGRATE)?

ANSWER: The neutrons in an atom acts like nuclear cement. it holds the protons together even if they try to repel.


For Characteristics of Fundamental Particles click here .docx



Four different scientists produced their own ideas of the atoms’ structure. 

  • John Dalton
  • JJ Thompson
  • Ernest Rutherford
  • Neils Bohr

John Dalton
The Postulates of Dalton

  • All matter is made of indivisible and indestructible atoms which are very tiny. (partially correct, they are tiny but yet divisible-discovery of subatomic particles.)
  • All atoms of a given element are identical in their physical and chemical properties. (was later proven wrong, due to discovery of Isotopes)
  • Atoms of different elements differ in their physical and chemical properties.(was later proven wrong, due to the discovery of isobars)
  • Atoms of different elements combine in simple whole number ratios to form compounds(later proven wrong, since they can combine in fractions.)
  • Chemical reactions consist of the combination, separation, or rearrangement of atoms.

JJ Thompson

As per his plum pudding model (there many names for this atomic model), Negatively charged particles are embedded in a Positive sphere.


Later proved wrong since this way electrons would fuse with the positive and the atom would cease to  be.


This way the Universe would collapse.


Ernest Rutherford

He conducted ‘the gold foil experiment’



Atomic Model of Rutherford is available in detail in next chapter.


ARYAMAN

any doubt – feel free to ask in the comment box


FOR MORE KNOWLEDGE VIEW CHAPTER TWO OF ‘ATOMIC STRUCTURE’

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