AQA GCSE Physics - ATOMIC STRUCTURE

Atoms are very small, having a radius of about

1x10-10 metres.

The nucleus of an atom is __________ charged

Positively

The nucleus contains 2 types of particle:

Protons and Neutrons

Protons are __________ charged

Positively

Neutrons have ____ charge

Zero

The nucleus is surrounded by _________

Electrons

Electrons are __________ charged

Negatively

The radius of a nucleus is less than _______ of the radius of an atom

1/10,000

Most of the mass of an atom is concentrated in the _______

Nucleus

The electrons are arranged at different _________ from the nucleus

Distances (Energy Levels)

When an electron absorbs electromagnetic radiation it moves to a ______ energy level

Higher (further from nucleus)

When an electron emits electromagnetic radiation it moves to a ______ energy level

Lower (closer to nucleus)

In an atom the number of electrons is equal to the number of _______ in the nucleus

Protons

Atoms have no overall electrical ______

Charge

All atoms of a particular element have the same number of _______

Protons

The number of protons in an atom of an element is called its ______ number

Atomic

The total number of protons and neutrons in an atom is called it's Atomic ____

Mass

Isotopes are atoms with more or less ________

Neutrons

Atoms turn into positive ions if they lose one or more outer _________

Electrons

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

Evidence

Before the discovery of the ________, atoms were thought to be tiny spheres that could not be divided

Electron

The discovery of the electron led to the ____ _______ model of the atom

Plum Pudding

The ____ _______ model suggested that the atom is a ball of positive charge with negative electrons embedded in it

Plum Pudding

The Plum Pudding model was replaced by the Nuclear Model of the atom using evidence from the _____ __________ experiment

Alpha Scattering

The Alpha Scattering experiment concluded that the ____ of an atom was concentrated in the Centre (Nucleus)

Mass

The Alpha Scattering experiment also concluded that the nucleus of the atom was _______

Charged

Niels Bohr adapted the nuclear model by suggesting that electrons _____ the nucleus at specific distances

Orbit

The theoretical calculations of Bohr ______ with experimental observations

Agreed

Later experiments found that the positive charge of a nucleus could be divided into a whole number of smaller particles, the name ______ was given to these particles

Proton

About 20 years after the nucleus became an accepted scientific idea, James Chadwick provided the evidence to show the existence of ________

Neutrons

Some atomic nuclei are ________

Unstable

An unstable _______ gives out radiation as it changes to become more stable

Nucleus

Radioactive _____ is a random process

Decay

________ measures how quickly unstable nuclei decay

Activity

Activity is measured in _________

Becquerel (Bq)

_____-____ is the number of decays recorded each second by a detector (eg Geiger-Muller tube)

Count-rate

An alpha particle (α) consists of two ________ and two protons

Neutrons

An alpha particle (α) is the same as a helium _______

Nucleus

A beta particle (β) - a high speed ________ ejected from the nucleus

Electron

A beta particle (β) is emitted when a neutron turns into a ______

Proton

A gamma ray (γ) is electromagnetic radiation from the _______

Nucleus

An unstable nucleus may emit an alpha, beta, gamma or a _______

Neutron (n)

An alpha particle can be stopped by _____

Paper

An alpha particle can travel _ ___ ___ through air

A few cms

An alpha particle has a ____ ionising power

High

A beta particle can be stopped by ____ _________

thin aluminium

A beta particle can travel _ _____ through air

1 Meter

A beta particle has a _____ ionising power than alpha

Lower

A gamma ray can be slowed by _____ ____

Thick Lead

A gamma ray can travel _ __ through air

1 km

A gamma ray has a ____ ___ ionising power

Very Low

A ___ ionising power means that healthy cells are not harmed during radiotherapy

Low

A ____ penetration power means that radiation can be detected through thick materials

High

A _____ half-life means the substance won't be radioactive for very long

short

In a nuclear equation an alpha particle may be represented by the symbol:

In a nuclear equation a beta particle may be represented by the symbol:

The emission of different types of nuclear radiation may cause a change in the mass and/or the ______ of the nucleus

Charge

Alpha decay causes both the mass and charge of the nucleus to ________

Decrease

Beta decay does not cause the ____ of the nucleus to change

Mass

Beta decay causes the charge of the nucleus to ________

Increase

The emission of a _____ ___ does not cause the mass or the charge of the nucleus to change

Gamma Ray

The half-life of a radioactive isotope is the time it takes for the number of unstable nuclei in a sample to _____

Halve

The half-life of a radioactive isotope is the time it takes for the count rate (or activity) from a sample to fall to ____ its initial level

Half

Radioactive _____________ is the unwanted presence of materials containing radioactive atoms on other materials

Contamination

The hazard from contamination is due to the decay of the contaminating _____

Atoms

Contaminating atoms which emit gamma rays are more hazardous at _____ distances

Large

Contaminating atoms which emit alpha particles are very hazardous at _____ distances

Short

At short distances, contaminating atoms which emit beta particles are ____ hazardous than alpha particles

Less

___________ is the process of exposing an object to nuclear radiation

Irradiation

An __________ object does not become radioactive

Irradiated

It is important for the findings of studies into the effects of radiation on humans to be published so that the findings can be checked by ____ ______

Peer Review

The peer review process allows information to be critiqued by- and ______ with other scientists

Shared

__________ radiation is around us all of the time

Background

_______ background radiation sources include rocks and cosmic rays from space

Natural

___-____ background radiation sources include the fallout from nuclear weapons testing and nuclear accidents

Man-made

The level of background radiation and radiation ____ you are exposed to may be affected by occupation and/or location

Dose

Radiation dose is measured in...

Sieverts (Sv)

____ millisieverts (mSv) = 1 sievert (Sv)

1,000

The ____-_____ of radioactive isotopes can be very short or very long

Half-lives

Medical radioactive isotopes with a long half-life pose a ____ risk to the patient

High

Nuclear radiations are used in ________ for the exploration of internal organs or destruction of unwanted tissue

Medicine

Nuclear _______ is the splitting of a large, unstable nucleus

Fission

For fission to occur the unstable nucleus must first absorb a _______

Neutron

A nucleus undergoing fission splits into two _______ nuclei

Smaller

A nucleus undergoing fission splits in two AND emits two or three ________ plus energy

Neutrons

All of the fission products have _______ energy

Kinetic

The neutrons emitted by a splitting nucleus in nuclear fission may go on to start a _____ ________

Chain Reaction

The chain reaction in nuclear fission is controlled in a nuclear reactor to control the ______ released

Energy

The explosion caused by a nuclear weapon is caused by an uncontrolled _____ ________

Chain Reaction

Nuclear ______ is the joining of two light nuclei to form a heavier nucleus

Fusion

In nuclear fusion some of the mass may be converted into ______

Energy