Atomic Structure

Question 1

Dalton’s Atomic Theory

Answer 1

1. All matter is made up of very tiny, indivisible particles, called atoms.
2. All atoms of a given element have the same properties. Conversely, atoms of different elements have different properties.
3. In ordinary chemical reactions, no atom disappears or changes into an atom of another element.
4. Compounds are formed by chemical combinations of two or more different kinds of atoms. In compounds, the relative numbers of atoms of different elements are constant and are commonly expressed as integers.
5. A molecule is a tightly bound combination of two or more atoms that acts as a single unit.

Question 2

Evidence for Dalton’s Atomic Theory

Answer 2

1. Law of Conservation of Mass
2. Law of Definite Composition
3. Law of Multiple Proportions

Question 3

Law of Conservation of Mass

Answer 3

Matter is neither created nor destroyed. The mass of reactants in a chemical reaction is always equal to the mass of products.

Question 4

Law of Definite Composition

Answer 4

Any compound is always made up of elements in the same proportion by mass. Percentage by mass of elements in a compound is always the same.

Question 5

Law of Multiple Proportion

Answer 5

When two elements combine to form more than one compound, the different masses of one element combin with the same mass of the other element are in a simple ration of whole numbers.

Question 6

Michael Faraday

Answer 6

• Law of Electrolysis
• Law of Electromagnetic Induction
• Discovered smallest unit of energy exists

Question 7

William Crookes

Answer 7

• Cathode Ray Tubes
• Electrical current is stream of negatively charged particles

Question 8

J.J. Thomson

Answer 8

• Better vacuum tube than Dalton
• If flow is composed of negatively charged particles, will be deflected by electric field
• Amount of deflection is dependent of mass of particle and magnitude of charge
• Angle of deflection is proportional to mass-charge ratio
• Indicated that particles have very low mass or very high charge

Question 9

Robert Millikan

Answer 9

• If mass and charge was measured, both would be known if value of ratio is known
• Electrical charge stored in oil droplets suspended in electric field
• Calculate charge on drop by measuring force needed to prevent drop from falling
• Charge always whole number multiple of certain value, the charge of the electron

Question 10

Plum Pudding Model

Answer 10

• Jell-O is positively charged, equal to neg charge of electrons
• Electrons are the plums embedded in Jell-o

Question 11

Rutherford Scattering Experiments

Answer 11

• Ernest Rutherford and Hans Geiger
• Beam of positively charged alpha particles directed at thin gold foil
• Plum Pudding - particles should pass through
• Some particles were deflected
• Nucleus in the center contains all positive charge of atom