Chapter 2

Question 1

Atomic Theory emergence

Answer 1

Reemerged in Europe 1803-1807 came from the work of John Dalton.
-During this time chemist became able to measure the amount of elements that reacted to one another.

Question 2

Atomic Theory

Answer 2

John Dalton

1. Each element is composed of extremely small particles called atoms.
2. All atoms of a given element are identical, but the atoms of one element are different from the atoms of all the other elements.
3. Atoms of one element cannot be changed into atoms of a different element by chemical reactions; atoms are neither created nor destroyed in chemical reactions.
4. Compounds are formed when atoms of more than one element combine; a given compound always has teh sae relative number and kind of atoms.

Question 3

Law of conservation of mass

Answer 3

the total mass of materials present after a chemical reaction is the same as the total mass present before the reaction.

Question 4

law of multiple proportions

Answer 4

If two element A and B combine to form more than one compound, the masses of B that can combine with a given mass of A are in the ratio of small whole numbers

Question 5

Cathode rays

Answer 5

radiation that travels between a negative cathode and travels to the positive electron when electricity is present.
i.e. beam of electrons

Question 6

J.J. Thomson

Answer 6

• British Scientist (1856-1940)
• Observed Cathode rays are the same regardless of the identity of the cathode material.
• In paper (1897) described cathode rays as streams of negatively charged particles. Generally excepted as the “discovery” of the electron.
• designed an experiment involving a cathode-ray tube with perpendicular magnetic and electric fields. This experiment produced a ratio of an electron’s electrical charge to it’s mass.

Question 7

Robert Millikan

Answer 7

• 1868-1953
• 1909 Robert Millikan succeeded in measuring the charge of an electron and then calculated the mass of the electron based off of Thomson’s charge to mass ratio.
• Did this through his oil-drop experiment

Question 8

Henri Becquerel

Answer 8

• 1852-1908
• 1896 discovered that a compound of uranium spontaneously emits high-energy radiation.
• suggested Marie Curie and her husband Pierre try to isolate the radioactive components of the compound.

Question 9

Cathode-ray Tube experiment

Answer 9

1897 J.J. Thomas

-discovery of an electron’s charge to mass ratio

Question 10

Oil-drop experiment

Answer 10

1909 Robert Millikan

-measured charge of electron and using Thomson’s charge-to- mass ratio calculated the mass of the electron.

Question 11

Ernest Rutherford

Answer 11

1871-1937

• revealed three types of radiation (alpha, beta, and gamma)
• 1910- Proposed an experiment in which alpha particles (positively charged) are shot through a thin sheet of gold.
• led to the nuclear model of the atom
• On New Zealand 100$ bill
• 1919-discovered proton

Question 12

James Chadwick

Answer 12

(1891-1972)

-1932-discovered neutron

Question 13

(a)

Answer 13

• alpha particles
• fast moving positive particles
• have a 2+ charge

Question 14

β

Answer 14

• Beta particles
• High-speed electrons
• radioactive equivalent of cathode rays
• have a 1- charge

Question 15

(y)

Answer 15

• Gamma Rays
• high-energy radiation
• does not consist of particles
• carries no charge

Question 16

Charge of an electron?

Answer 16

-1.602 x 10^-19 C
therefore a protons charge is:
1.602 x 10^-19 C

Question 17

what unit of length is used for atomic dimensions?

Answer 17

angstrom (Å) = 1 x 10^-10m