Models Of Atomic Structure

Question 1

What did Democritus say about atoms

Answer 1

Everything is made up of atoms which are tiny indivisible particles

Question 2

Why did Democritus fail to convince anybody that his theory was correct

Answer 2

He did not do experiments so had no way to test his theory about atoms

Question 3

Main points of daltons atomic theory

Answer 3

-elements made up of indivisible atoms(atoms of same element are identical with same mass)
-atoms of dif elements have dif masses
-atoms can combine to form molecules in compounds-molecules of compound are identical

Question 4

What did JJ Thomson discover

Answer 4

Discovered electrons which were particles smaller than atoms, knew that atoms had overall no electrical charge so rest of atom must be positive. Created plum pudding model-atoms balls of positive material with electrons embedded in them

Question 5

Describe Rutherford’s alpha scattering experiment and what did they expect to find

Answer 5

Directed narrow beams of alpha particles(knew they were positive) at a very thin gold foil sheet only a few atoms thick.
-expected particles to pass straight through foil or deflected slightly

Question 6

Results of the alpha scattering experiment and conclusions drawn from these

Answer 6

-most alpha went straight through=atoms mainly empty space
-very few alpha deflected by foil=atoms have small positively charged nucleus due to protons where mass of atom is concentrated
-rarely rebounded from foil=some alpha particles approached gold atom nucleus ‘head on’

Question 7

Describe the model that came as a result of the alpha scattering experiment

Answer 7

The nuclear model-very small positive nucleus surrounded by much larger region of empty space in which electrons orbit the nucleus

Question 8

What did James Chadwick discover

Answer 8

Proved that there must be uncharged particles in the nuclei of atoms(neutrons) which helps to explain isotopes and the relative masses of elements (eg helium is 4 not 2 as it has 2 neutrons as well as 2protons)

Question 9

Oder that subatomic particles were discovered in and by who

Answer 9

-electrons by JJ Thomson
-protons by Rutherford
-neutrons by James Chadwick

Question 10

How many neutrons does hydrogen have

Answer 10

None

Question 11

What is the atomic number of an element and it’s symbol

Answer 11

The number of protons in the nucleus of an atom
-symbol= Z

Question 12

What is the mass number of an element and it’s symbol

Answer 12

Total number of protons and neutrons in the nucleus of an atom
-symbol=A