Scientists

Chemistry Page

It is important to have some knowledge about the major scientists involved in the major discoveries of chemistry. This is often only a short question in Q4 or a 3 marker in a long question, but its an easy way to add marks

Boyle

• An element is a substance that cannot be broken down into simpler materials
• Boyle’s Law

Davy

• Developed electrochemical techniques for breaking down compounds
• Use of electrolysis

Moseley

• Discovery of atomic numbers
• Use of X rays in the discovery of a characteristic positive charge in the nucleus

Dobereiner

• Law of Triads
• Groups of three elements have similar properties

Newlands

• Law of Octaves
• Properties repeat every eight elements

Mendeleev

• Periodic table
• Left gaps for undiscovered elements
• Ordered by atomic weights
• Iodine and tellurium the exception (atomic number later explained this)

Dalton

• First atomic theory based on experimental evidence
• Indirect evidence
• Atoms are indivisible and indestructible
• Atoms of a given element are identical
• Atoms of different elements vary in mass
• Compound contains atoms combined in fixed proportions
• Law of conservation of mass

Crookes

• Cathode rays are particles (moved a small paddle)

Thompson

• Cathode rays have negative charge
• Negatively charged particles are extremely light
• Plum pudding model of the atom – electrons embedded in a positively charged sphere

Stoney

• Suggested name “electron”

Millikan

• Oil drop experiment
• Electrical force used to suspend drops mid air
• Electron charge accurately measured

Rutherford

• Alpha particles fired at gold foil
• Large number not deflected (empty space)
• Very small numberbounced back (concentrated positive charge)
• Discovery of nucleus
• Positive charge confined to nucleus
• Discovery of proton

Chadwick

• Aplha particles fired at beryllium
• Alpha particles >>>knocks out>>> neutrons in Be >>>knocks out>>> protons in parafin >>>detected
• Discovery of neutron

Bequerel

• Study of chemicals which emitted light and X rays, which had been exposed to white light
• Photographic plate in black paper with crystals of uranium – placed in sunlight – image of crystals developed
• Without sunlight, image still developed
• Crystals emitted radiation which caused image
• Radiation also ionised air – air conducts electricity

Curie

• Coined term “radioactivity”
• Discovered that amount of radiation depended on proportion of uranium
• Isolated new elements (polonium and radium) which are more radioactive than uranium
• 1903 Nobel Prize (with Bequerel and her husband) – discovery of radioactivity
• 1911 Nobel Prize – discovery of elements