History Of The Atom

Question 1

Who were the scientists from 500BC - 1940 that came up with theories of Atoms

Answer 1

Democritus
John dalton
J.J Thomson
Ernest Rutherford
Niels Bohr
James Chadwick

Question 2

When did Democritus come up with his theory

Answer 2

500BC

Question 3

When did John Dalton come up with his theory

Answer 3

1800’s

Question 4

When did J.J Thomson come up with his theory

Answer 4

1897

Question 5

When did Ernest Rutherford come up with his theory

Answer 5

1901

Question 6

When did James Chadwick come up with his theory

Answer 6

1932

Question 7

What was Democritus theory

Answer 7

Atomic Theory, idea of ‘ stuff ‘ (everything) is made up of tiny little particles, that can’t be broken down any futher, separated from each other by empty space

Question 8

What was John Dalton theory

Answer 8

**’ Solid Spheres ‘ **, different types of spheres might make up the different elements.

Question 9

What was J.J Thomson theory

Answer 9

** Plum Pudding Model , atoms couldn’t be solid spheres, instead must of contained negative charged particles (e-**).
=> Atoms where a general Ball of Positive Charge with Discrete electrons in it .

Question 10

What was Ernest Rutherford theory

Answer 10

Nuclear Model, compact nucleus which containas all the positive charge of the atom. Thought that negative charge must exist in some sort of cloud around the central nucleus. => Atoms should automatically collapse ( we know it doesn’t )

Question 11

What did Ernest Rutherford shortly find out after Niels Bohr

Answer 11

He found out that positive charge in nucleus is made up of small discrete particles ( protons )

Question 12

What was James Chadwick theory

Answer 12

Neutrons, neutral particles in the nucleus

Question 13

Who were the scientists behind the development of the periodic table

Answer 13

** Johann Döbereiner**
Newland
** Dmitri Mendeleev**

Question 14

What did Johann Döbereiner do to develop the periodic table

Answer 14

discovered the existence of families of elements with similar chemical properties. Because there always seemed to be three elements in these families, he called them triads. Each of the vertical columns in Table 7.1 represents one of these triads.

Question 15

What did Newland do to develop the periodic table

Answer 15

Law of octaves, He arranged the elements in order of increasing atomic weight, every eighth element reacts in similar way.

Question 16

What did Dmitri Mendeleev do to develop the periodic table

Answer 16

Developed first modern periodic table. Mendeleev ostensibly organized his table by increasing atomic weight, but he gave chemical properties a deciding vote. For example, tellurium is slightly heavier than iodine, but Mendeleev put tellurium first because it has the same valence as oxygen, sulfur, and other elements in its group.

Question 17

Differences from old and modern periodic tables

Answer 17

• modern periodic table, elements are arranged in order of atomic numbers ( other words, protons )
• Protons had not been discovered during Mendeleevs time, ordered elements by atomic weight. ( elements can be in the wrong order due to the presence of isotopes)
• Modern periodic table has group 0: noble gases ( hadn’t been discoverd during Mendeleevs time).