Atoms and isotopes (4.1) (R)

Question 1

What is the radius of an atom?

Answer 1

1 x 10^-10m

Question 2

Describe the basic structure of the atom

Answer 2

A positively charged nucleus composed of both protons and neutrons surrounded by negatively charged electrons.

Question 3

What is the ratio of the radius of the nucleus to the radius of the atom?

Answer 3

1:10 000

Question 4

Where is most of the mass of an atom concentrated?

Answer 4

the nucleus

Question 5

The electrons are arranged at different (…) from the nucleus i.e. different (…)

Answer 5

distances

energy levels

Question 6

The absorption or emission of what may change the electron arrangements?

Answer 6

the absorption and emission of electromagnetic radiation

Question 7

How does the absorption of electromagnetic radiation change the electron arrangement?

Answer 7

electrons move further from the nucleus to a higher energy level

Question 8

How does the emission of electromagnetic radiation change the electron arrangement?

Answer 8

electrons move closer to the nucleus to a lower energy level

Question 9

What is electromagnetic radiation?

Answer 9

energy from light (only some is visible light)

Question 10

In an atom the number of electrons is (…) to the number of protons in the nucleus.

Answer 10

equal

Question 11

What is the overall electrical charge of an atom?

Answer 11

there is no overall electrical charge

Question 12

All atoms of a particular element have the same number of what?

Answer 12

protons

Question 13

What is the atomic number?

Answer 13

The number of protons (in an atom of an element)

Question 14

What is the mass number?The total number of protons and neutrons in an atom

Answer 14

The total number of protons and neutrons in an atom

Question 15

What are isotopes?

Answer 15

Atoms of the same element that have different numbers of neutrons

Question 16

What are isotopes?

Answer 16

Atoms of the same element that have different numbers of neutrons

so different mass

Question 17

If atoms lose one or more outer electron(s), they turn into what?

Answer 17

positive ions

Question 18

What is the use of new experimental evidence?

Answer 18

New experimental evidence may lead to a scientific model being changed or replaced

Question 19

Before the discovery of the electron, what were atoms thought to be?

Answer 19

tiny spheres that could not be divided

Question 20

The discovery of the electron led to which model?

Answer 20

the plum pudding model of the atom

Question 21

Describe the plum pudding model

Answer 21

that the atom is a ball of positive charge with negative electrons embedded in it

Question 22

What did the results from the alpha particle scattering experiment show?

Answer 22

that the mass of an atom was concentrated at the centre (nucleus) and that the nucleus was charged

Question 23

Which model did the results from the alpha particle scattering experiment lead to, replacing the plum pudding model?

Answer 23

The nuclear model

Question 24

How did Niels Bohr adapt the nuclear model? How did he prove this?

Answer 24

by suggesting that electrons orbit the nucleus at specific distances (in shells)

the theoretical calculations of Bohr agreed with experimental observations

Question 25

How did later experiments lead to the discovery of the proton?

Answer 25

They led to the idea that the positive charge of any nucleus could be subdivided into a whole number of smaller particles, each particle having the same amount of positive charge. The name proton was given to these particles.

Question 26

What did the experimental work of James Chadwick prove the evidence to show?

Answer 26

the existence of neutrons within the nucleus

Question 27

How long was there between Chadwick's proof of the **neutron** and the **nucleus** becoming an accepted scientific idea?

Answer 27

about 20 years

Question 28

How did the alpha particle scattering experiment lead to a change in the atomic model?

Answer 28

Geigar and Marsden fired very dense, positive particles, known as alpha particles, at a thin piece of gold foil. They expected all particles to pass straight through and be detected using a screen. However, while most did, many diverged and some rebounded. Thus, Rutherford theorised that the atomic model must be wrong as the alpha particles must have rebounded off a centre of dense positive particles (nucleus) with electrons orbiting it.

Question 29

What is the difference between the plum pudding and nuclear models?

Answer 29

In the plum pudding model, the atom as a ball of positive charge with negative electrons embedded within it, whereas in the nuclear model, the positive charged is concentrated at a dense centre (nucleus) *Also the later nuclear model has shells of electrons orbiting it at specific distances (after Bohr's work)*