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Flashcards in Atomic Structure Deck (58)
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1

Scientists

John Dalton
William Crookes
George Johnstone Stoney
J.J Thomson
Robert Milikan
Ernest Rutherford
Niels Bohr
James Chadwick

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John Dalton- discovered

Atomic theory

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John Dalton - how

Through experiments he performed with gases

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William Crookes - discovered

Cathode rays

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William Crookes - how

Negative electrode rays cast shadow of maltese cross in a vacuum tube

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George Johnstone Stoney - discovered

Named the electron

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George Johnstone Stoney - how

Proposed name in 1981

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J.J Thomson - discovered

Electrons have a negative charge

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J.J Thomson - how

-Sent cathode ray through positive electrode, then through 2 parallel plates
-When plates weren't charged, ray went straight through, but if top one was positive, ray went upwards

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Robert Millikan - discovered

Magnitude of charge of electrons as shown by oil drops experiment

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Robert Millikan - how

-Sprayed tiny oil droplets between 2 charged metal plates, used x-rays to ionise air between plates
-Oil droplets fell through air
-Oil droplet attached to positively charged plate
-Made the droplet stationary + from measurements, he was able to calculate charge of electron

12

Ernest Rutherford - discovered

Discovering of nucleus as shown by particle scattering experiment, discovering of protons in nuclei of various atoms

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Ernest Rutherford - how

-Bombarded gold foil with Alpha particles
-used detector for scattered a-particles
-most went straight through, some deflected largely, some reflected

- showed that gold foil had nuclei - which when hit, positive alpha particles repelled them

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Niels Bohr - discovered

Model of atom

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Niels Bohr - how

Used experimental evidence to prove electrons occupy particular orbits or shells around nucleus of atom

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James Chadwick - discovered

Discovered the neutron

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James Chadwick - how

-Bombarded beryllium with alpha particles
-Discovered some particle with no charge was coming from beryllium
-They were knocking protons from beryllium
-Found that these particles had same mass as protons + named them neutrons

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Dalton's Atomic Theory

1. All matter is made up of very small particles called atoms
2. All atoms are indivisible. Cannot be broken down into simpler particles


(3. identical atomic mass for particular element)

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Thomson's plum pudding

1. Atom is like a sphere of positive charge
2. Electrons embedded in sphere at random

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Problem with Plum Pudding model

Explained why atoms were neutral but Thomson did not have experimental evidence

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Mass Spectrometer

Instrument capable of separating + recording relative amounts of isotopes of an element.

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Mass Spectrometer topics (processes)

Sample intro
Vaporisation
Ionisation
Separation of ions
Detection

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Mass Spectrometer

-Sample to be analysed is injected into instrument
-Vaporised
-Ionised by bombardment with beam of high-energy electrons.
-Positive ions produced are accelerated through slit, using electric field, deflected along circular path using magnetic field
-Degree of curvature depends on mass of ion)
-Separated into beams of ions of similar masses in this way
-Detected electronically
-Vacuum inside so ions don't clash with air molecules

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Mass Spectrometer - molecules

-Can be used to determine relative molecular mass of substance composed of molecules
-Molecules ionised + broken into positively charged fragments w/ different masses
-Separated
-Relative amounts recorded, giving mass spectrum of molecume
-Mass of this ion is same as relatie molecular mass of molecule

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Molecule

Group of atoms joined together. It is the smallest particle of an element or compound that can exist independently

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Ion

Charged atom/group of atoms

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Compound

Substance made of two or more elements

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Atom

Basic unit from which all substances are formed

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Relative Atomic Mass (Ar)

Average of the mass numbers of the isotopes of the element as they occur naturally taking their abundances into account relative to the 1/12th mass of carbon 12 atom

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Isotope

Atoms of the same element that have different mass numbers due to different number of neutrons in nucleus