Atomic Structure- Development of Model of Atom

Question 1

J.J. Thompson discovered the ________ (tiny negatively charged particles) and described atoms like ‘____ _________’ with negative charges embedded in a cloud of positive charge.

Answer 1

J.J. Thompson discovered the electron (tiny negatively charged particle) and described atoms like ‘plum puddings’ with negative charges embedded in a cloud of positive charge.

Question 2

Geiger and Marsden’s did experiments firing positive _____ particles at ____foil which showed atoms could not be _____.

Answer 2

Geiger and Marsden’s did experiments firing positive alpha particles at gold foil which showed atoms could not be solid.

Question 3

__________ proposed that the positive charge of an atom is in a small centre which he called the nucleus and electrons _____ this nucleus. (This is the _______ model)

Answer 3

Rutherford proposed that the positive charge of an atom is in a small centre which he called the nucleus and electrons orbit this nucleus. ( This is the nuclear model)

Question 4

In 1914 Niels ____ suggested electrons orbit at set distances in ______ _______ (or shells)

Answer 4

In 1914 Niels Bohr suggested electrons orbit at set distances in energy levels (or shells)

Question 5

In 1932 James Chadwick discovered the _______ which has __ ______ and has the same ____ as a proton

Answer 5

In 1932 James Chadwick discovered the neutron which has no charge and has the same mass as a proton

Question 6

Dalton thought atoms were hard ________ and that elements had only ___ ____ of atom.

Answer 6

Dalton thought atoms were hard spheres and that elements had only one type of atom.

Question 7

what did the ancient greeks think about atoms

Answer 7

that they were tiny spheres which could not be divided - this idea was accepted for hundreds of years

Question 8

when did scientists discover that there were tiny negative particles

Answer 8

1987

Question 9

what did the discovery of tiny negative particles (electrons) tell scientists

Answer 9

that atoms were not tiny spheres that couldn’t be divided

Question 10

how did scientists prove whether the plum model was accurate or not

Answer 10

they carried out an experiment called the alpha scattering experiment

Question 11

explain the alpha scattering experiment

Answer 11

1. scientists took a piece of gold foil - they used gold as it could be made to only be a few atoms thick
2. they then fired alpha particles at the gold foil

Question 12

where did most of the alpha particles go?
if they didn’t go here where did they go?

Answer 12

most alpha particles passed straight through the gold foil without changing direction
some were deflected - changed direction
some bounced straight back off the gold foil

Question 13

explain how the course of each particle led too a conclusion about an atom

Answer 13

straight through - atom is mostly empty space
deflected - centre of atom must be positive
bounced back - center of atom has great deal of mass

Question 14

what model replaced the plum pudding model

Answer 14

nuclear model

Question 15

what does the number of protons determine

Answer 15

the amount of positive charge in the nucleus