History of the atom

Question 1

What was the first mention of atoms

Answer 1

• Democritus in 500 BC
• Atoms are solid spheres that make up all things seperated from eachother by empty space
• Atomic theory

Question 2

Who came up with the theory regarding solid spheres

Answer 2

• John Dalton
• Atoms were solid spheres
• Different types of solid spheres made up different elements

Question 3

What was the plum pudding model

Answer 3

• Proposed by J.J Thompson
• An atom was a ball of positive charge with negative electrons embedded in it

Question 4

What was the nuclear model

Answer 4

• Proposed by Ernest Rutherford
• An atom had most of its mass located in the centre in a positivley charged nucleus with a negatively charged cloud surrounding it

Question 5

What was wrong with the nuclear model

Answer 5

• There was nothing to stop the cloud of negative charge to collapse and enter the positive nucleus

Question 6

What experiment did Ernest Rutherford carry out

Answer 6

• Fires alpha particles at a thin sheet of gold
• If J.J Thompson’s PPM was correct than the alpha particles would go straight through the sheet however, some were deflected. This proved that there was a centre of the atom where most of the mass was located (nucleus)

Question 7

What was discovered by Niels Bohr

Answer 7

• Discovered that electrons orbitted the nucleus in shells

Question 8

What was discovered by Ernest Rutherford regarding the sub atomic particles

Answer 8

• The nucleus is comprised of positively charged protons

Question 9

What was discovered by James Chadwick

Answer 9

• The nucleus also contains neutral neutrons