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Unit 1 Lesson 1

Title: Structure of the atom

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On your whiteboard, write the names

of structures A, B, C and D.

nucleuselectron

neutronproton

AB

CD

Starter – The diagram shows an

atom

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• Most – Describe the position of protons and

neutrons within the nucleus

• Some – Explain the existence of isotopes

Specification statements

• Describe relative charge and relative mass of

protons, neutrons and electrons.

• Describe the distribution of mass and charge

within the atom.

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The nucleus contains ________ and ________.

It is very dense – it contains nearly all the mass of

the atom in a tiny space.

________ are:

• very small and light, and _________ charged;

and

• found around the outside of the nucleus,

orbiting in layers called shells.

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The nucleus contains protons and neutrons.

It is very dense – it contains nearly all the mass of

the atom in a tiny space.

Electrons are:

• very small and light, and negatively charged;

and

• found around the outside of the nucleus,

orbiting in layers called shells.

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AfL – On your whiteboards write the letter for the correct

charges on each of the particles

D

A

B

C

D

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The link between electrons and protons

• In an atom, the number of electrons is equal

to the number of protons.

• Atoms have no overall electrical charge.

• The number of protons in an atom of an

element is its atomic number.

• The sum of the protons and neutrons in an

atom is its mass number.

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Deduce the number of protons, neutrons and

electrons in an atom of;

1. Calcium

2. Oxygen

3. Aluminium

4. Bromine

5. Platinum

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The smallest particle that can exist on its own.

Negatively charged particle that orbits the nucleus of an atom.

A substance made up of only one type of atom.

The dense, positively charged centre of an atom, made up of

protons and neutrons.

atom

electron

element

nucleus

Glossary – copy into your notes

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Properties of isotopes

The isotopes of an element are virtually identical in their chemical reactions.

The uncharged neutrons make no difference to chemical properties but do affect physical

properties such as melting point and density.

Natural samples of elements are often a

mixture of isotopes.

This is because they have the same number of protons and the same number of electrons.

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Isotopes of carbonMost naturally-occurring carbon exists as carbon-12, about 1% is carbon-13 and a much smaller amount is carbon-14.

6 protons

7 neutrons

6 electrons

6 protons

8 neutrons

6 electrons

6 protons

6 neutrons

6 electrons

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Isotopes of hydrogenHydrogen-1 makes up the vast majority of the naturally-occurring element but two other

isotopes exist.

hydrogen deuterium tritium

1 proton

0 neutrons

1 electron

1 proton

1 neutron

1 electron

1 proton

2 neutrons

1 electron

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Isotopes of chlorineAbout 75% of naturally-occurring chlorine is chlorine-35 and 25% is chlorine-37.

17 protons

18 neutrons

17 electrons

17 protons

20 neutrons

17 electrons

What are the particle numbers in each isotope?

8

8

8

8

8

10

oxygen-16

AfL - whiteboards

oxygen-18

protons

neutrons

electrons

Isotopes of oxygenAlmost all of naturally-occurring oxygen is oxygen-16 but about 0.2% is oxygen-18.

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Homework – IMOD

(Independent study module or

task)Create a timeline or flow chart of the

development of ideas about the atom.

Key scientists to include are;

John Dalton

J. J. Thompson

Ernest Rutherford

Henry Moseley

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Describe the position of protons and neutrons

within the nucleus

Explain the existence of isotopes

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Plenary

On your exit ticket write;

• One thing you have learned in today’s lesson.

• One thing you didn’t understand or would

like to spend more time on.

• One interesting thing that you are going to

research as a result of today’s lesson.