atoms and subatomic particles -...

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Atoms and Subatomic Particles

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Atoms and Subatomic Particles

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What are atoms made of?

What is the size of one atom in nanometres (nm)?

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What particles are atoms made of?

protons neutrons electrons

Atoms are made up of three smaller, or subatomic, particles:

The electrons are spread out

around the edge of the atom.

They orbit the nucleus in layers

called shells (energy levels).

The protons and neutrons exist in a

dense core at the centre of the atom.

This is called the nucleus.

The radius of a nucleus is less

than 1/10,000 of that of the atom.

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particle relative mass relative chargeproton

neutron

electron

There are two properties of protons, neutrons

and electrons that are especially important:

relative mass

relative electrical charge.

The atoms of an element contain equal numbers of protons and electrons and so have no overall charge.

-1almost 0

01

+11

Mass and electrical charge

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Properties of subatomic particles

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Discovering atomic structure

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Summary: atomic structure

The nucleus is:

made up of protons and neutrons

positively charged because of the

protons

dense because it contains most of the

mass of the atom in a tiny space.

Electrons are:

very small and light, and negatively charged

able to be lost or gained in chemical reactions

found thinly spread around the outside of the nucleus,

orbiting in layers called shells (energy levels).

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Atoms and Subatomic Particles

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How many protons?

Each element has a definite and fixed number of protons.

The atoms of any particular element always contain the

same number of protons. For example:

The number of protons in an atom is known as the atomic number or proton number.

It is the smaller of the two numbers

shown in most periodic tables.

hydrogen atoms always contain 1 proton

carbon atoms always contain 6 protons.

If the number of protons changes, then the atom becomes

a different element.

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sodium

iron

tin

fluorine

The atomic number (proton number)

What are the atomic (proton) numbers of these elements?

11

26

50

9

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What is mass number?

Electrons have a mass of almost zero, which means that the

mass of each atom results almost entirely from the number

of protons and neutrons in the nucleus.

The sum of the protons and neutrons in an atom’s nucleus is the mass number.

1413aluminium

43lithium

01hydrogen

neutronsprotonsatoms mass number

27

71

It is the larger of the two numbers shown

in most periodic tables.

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mass number = number of protons + number of neutrons

What is the mass number?

What is the mass number of these atoms?

3227

3529

22

59

64

4

cobalt

copper

helium

neutronsprotonsatoms mass number

iodine

germanium

53

32

74

41 73

127

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Building a nucleus

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What are the missing numbers?

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Sodium (Na) can form an Na+ ion.

11 protons

12 neutrons

10 electrons

Na+ has a charge of +1 because it has lost one electron,

and has one more proton than electrons.

How many protons, electrons and neutrons does Na+ have?

Use the tile from the periodic table below to help you.

Charged particles: ions

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Atoms and Subatomic Particles

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Introduction to electron shells

A Danish scientist called Niels Bohr suggested that electrons

orbit the nucleus in fixed energy levels called shells.

The arrangement

of electrons can be

written from the

lowest energy level

to the highest.

1st shell holdsa maximum of

2 electrons

2nd shell holds

a maximum of

8 electrons

3rd shell holds

a maximum of

8 electrons

Each shell has a maximum number of electrons that it is able

to hold. Electrons fill the shells nearest the nucleus first.

This electron arrangement of this

atom is written as 2,8,8.

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How are electrons arranged?

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Calculating electron arrangement

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Atoms and Subatomic Particles

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Glossary

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True or false?

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Multiple-choice quiz