ks4 atomic structure

7/27/2019 KS4 Atomic Structure

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KS4 Chemistry

Atomic Structure


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Atomic Structure

Electron configuration

Summary activities

Isotopes

Introducing atoms

Atomic number and mass number

Contents


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Discovery of atomic structure


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Atoms the building blocks

All substances are made from very tiny particles called atoms.

John Dalton had ideas about theexistence of atoms about 200 years

ago but only relatively recently have

special microscopes (called

electron microscopes) beeninvented that can see atoms.

The yellow blobs in this image are

individual gold atoms, as seenthrough an electron microscope.


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Elements different types of atom

Elements are the simplest substances. There are about

100 different elements.

Each element is made up of just one particular type of atom,

which is different to the atoms in any other element.

Copperis anelement made up ofcopper atoms only.

Carbon is anelement made up ofcarbon atoms only.


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How small is an atom?

Atoms are extremely small they are about 0.00000001cm

wide.

N X3,000,000,000

If a football was enlarged

by the same amount itwould stretch from the

UK to the USA.

To make an atom the size of a football it would have to be

enlarged by about 3,000,000,000 times.


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The Amazing Atomic Zoom


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Inside an atom

Where are the electrons and nucleus found in an atom?


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Atomic Structure


Summary activities

Isotopes

Introducing atoms


Contents


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How heavy is an atom?

A single grain of sand contains millions of atoms of silicon

and oxygen.

Each atom must therefore have an extremely small mass.

millions of these atoms

join to form each tiny

grain of sand

Si

O

O


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Relative atomic mass

Atoms are so small that their mass is not measured in grams

but in atomic mass units.

Relative atomic mass = 12C

The element carbon is the atom that the mass of all otheratoms is compared to. Carbon has a RAM of 12.

The atoms of each type of element have a relative atomic

mass (RAM).



Relative atomic mass examples

The lightest atom is hydrogen. It has 112 the mass of carbon

and so has a RAM of 1.

Mg

Magnesium is twice as heavy as carbon. It has a RAM of 24.

HH H

HHH

HH

HH HH

HH H

HHH

HH

HH HH C

12 atoms x 1 = 1 atom x 12

CCMg

1 atom x 24 = 2 atoms x 12



Even smaller particles

For some time people thought that atoms were the smallest

particles and could not be broken into anything smaller.

proton

neutron

electron

Scientists now know that atoms are actually made from even

smallersubatomic particles. There are three types:



Where are subatomic particles found?

Protons, neutrons and electrons are NOT evenly distributed in

an atom.

The electrons are

spread out around the

edge of the atom. Theyorbit the nucleus in

layers called shells.

The protons and neutrons

exist in a dense core at the

centre of the atom. This is

called the nucleus.



The atom: check it out!

Draw a labelled diagram of the atom showing the nucleus

and labelling protons, neutrons and electrons.

nucleus

neutron proton

electron



Particle Mass Chargeproton 1 +1

neutron 1 0

electron almost 0 -1

Properties of subatomic particles

There are two properties of subatomic particles that are

especially important:

1. Mass

2. Electrical charge

The atoms of an element contain equal numbers of

protons and electrons and so have no overall charge.



How many 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 its atomic number

orproton 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;

magnesium atoms always contain 12 protons,



Whats the atomic number?

What are the atomic numbers of these elements?

11

sodium

26

iron

50

tin

9

fluorine



More about atomic number

Each element has a definite and fixed number of protons.

If the number of protons changes, then the atom becomes

a different element.

Changes in the number of particles in the nucleus

(protons or neutrons) is very rare. It only takes place in

nuclear processes such as:

radioactive decay;

nuclear bombs;

nuclear reactors.



Atom Protons Neutrons Mass number

hydrogen 1 0 1

lithium 3 4 7

aluminium 13 14 27

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 atoms nucleus is the mass number.

It is the larger of the two numbers shownin most periodic tables.

Wh h b ?



127

Whats the mass number?

What is the mass number of these atoms?

73

59

64

4

Mass number = number of protons + number of neutrons

Atom Protons Neutrons Mass numberhelium 2 2

copper 29 35

cobalt 27 32

iodine 53 74

germanium 32 41

H t ?



How many neutrons?

How many neutrons are there in these atoms?

Atom Massnumber

Atomicnumber

Number ofneutrons

helium 4 2

fluorine 19 9

strontium 88 38

zirconium 91 40

uranium 238 92

51

146

50

10

2

Number of neutrons = mass number - number of protons

= mass number - atomic number

B ildi l



Building a nucleus

C t t



Atomic Structure


Summary activities

Isotopes

Introducing atoms


Contents

H l t ?



Atom Protons Neutrons Electrons

helium 2 2 2

copper 29 35 29

iodine 53 74 53

How many electrons?

Atoms have no overall electrical charge and are neutral.

This means atoms must have an equal number of

protons and electrons.

The number of electrons is therefore the same as

the atomic number.

Atomic number is defined as the number of protons rather

than the number of electrons because atoms can lose or

gain electrons but do not normally lose or gain protons.

C l l ti th b f l t



Atom Protons Neutrons Electrons Atomic

number

Mass

number

boron 5 6

potassium 19 20

chromium 24 28

mercury 80 121

argon 18 22

Calculating the number of electrons

5

19

18

24

80

5

19

18

24

80

11

39

40

52

201

What are the missing numbers?

H l t d?



How are electrons arranged?

Electrons are not evenly spread but exist in layers

called shells.

3rd shell

2nd shell

1st

shell

The arrangement of electrons in these shells is often called

the electron configuration.

Ho man electrons per shell?



How many electrons per shell?

Each shell has a maximum number of electrons that it can

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

3rd shell holds

a maximum of

8 electrons

2nd shell holds

a maximum of

8 electrons

1st shell holdsa maximum of

2 electrons

Calculating electron configurations



Calculating electron configurations

Properties of the nucleus and electrons


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Properties of the nucleus and electrons

Summary: the atom so far


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Thinly spread around the outside

of the atom.

Very small and light.

Negatively charged.

Found orbiting the nucleus in layers called shells.

Able to be lost or gained in chemical reactions.

Summary: the atom so far

The nucleus is:

Electrons are:

Dense it contains nearly all the mass

of the atom in a tiny space. Made up of protons and neutrons.

Positively charged because of the

protons.

Contents


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Atomic Structure


Summary activities

Isotopes

Introducing atoms


Contents

What is an isotope?


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What is an isotope?

Elements consist of one type of atom, but sometimes these

atoms can be slightly different.

mass number

is different

atomic number

is the same

Atoms that differ in this way are called isotopes.

Although atoms of the same element always have the same

number of protons, they may have different numbers of

neutrons.

Properties of isotopes


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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 meltingpoint and density.

Natural samples of elements areoften a mixture of isotopes.

This is because they have the same number of protons and

the same number of electrons.

Isotopes of carbon


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Isotopes of carbon

Most naturally-occurring carbon exists as carbon-12, about1% is carbon-13 and a much smaller amount is carbon-14.

6 protons

6 neutrons

7 electrons

6 protons

6 neutrons

8 electrons

6 protons

6 neutrons

6 electrons

Isotopes of hydrogen


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Isotopes of hydrogen

Hydrogen-1 makes up the vast majority of the naturally-

occurring element but two other isotopes exist.

hydrogen deuterium tritium

1 proton

0 neutrons1 electron

1 proton

1 neutron1 electron

1 proton

2 neutrons1 electron

Isotopes of chlorine


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Isotopes of chlorine

About 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

Isotopes of oxygen


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What are the

particle

numbers ineach isotope?

10

8

8

8

8

8

oxygen-16 oxygen-18

protons

neutrons

electrons

Isotopes of oxygen

Almost all of naturally-occurring oxygen is oxygen-16 but

about 0.2% is oxygen-18.

Isotopes and RAM


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Isotopes and RAM

Many elements are a mixture of isotopes. The RAM given in

the periodic table takes account of this.

For example, chlorine exists as two isotopes:

chlorine-35 (75%) and chlorine-37 (25%).

To calculate the RAM of a mixture of isotopes,

multiply the percentage of each isotope by its

atomic mass and add them together.

= (0.75 x 35) + (0.25 x 37)

= 26.25 + 9.25

= 35.5

RAM of chlorine= (75% x 35) + (25% x 37)

Calculating RAM


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Calculating RAM

Bromine contains 50.5% bromine-79 and 49.5% bromine-81.

= (0.505 x 79) + (0.495 x 81)

= 39.895 + 40.095= 79.99

= 80 (the RAM is usually rounded

to the nearest whole number)

RAM of bromine= (50.5% x 79) + (49.5% x 81)

What is the RAM of naturally-occurring bromine?

Summarizing atomic structure


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Summarizing atomic structure

Atomic structure word check


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Atomic structure word check

Contents


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Atomic Structure


Summary activities

Isotopes

Introducing atoms


Contents

Glossary (part 1)


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Glossary (part 1)

atomThe smallest particle that can exist on its own.

atomic numberThe number of protons in the nucleusof an element, also known as the proton number.

electronNegative particle that orbits the nucleus of anatom.

elementSubstance made up of only one type of atom.

isotopesDifferent atoms of the same element. They havethe same number of protons and electrons, but a differentnumber of neutrons.

Glossary (part 2)


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Glossary (part 2)

nucleusThe dense positive centre of an atom, made upof protons and neutrons.

neutronA neutral particle, with a mass of 1. It is found inthe nucleus of an atom.

mass numberThe number of protons and neutrons inan atom.

protonA positive particle, with a mass of 1. It is found inthe nucleus of an atom.

relative atomic mass (RAM)The mass of anelement compared to the mass of112 of the mass of

carbon-12.

Anagrams


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Anagrams

Atomic structure word search


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Atomic structure word search



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Multiple-choice quiz


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Multiple choice quiz

ks4 atomic structure

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