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StudyPacks
STUDY.
KS4
SCIENCE
Chemistry Basics
The Atom
This Study Pack aims to cover:
1. The atomic structure.
2. Elements and compounds
SC1
Study Packs are prepared by Qualified Teachers and Specialists and are a complete range of comprehensive
compiled resources based on the UK National Curriculum covering the Primary and Secondary Frameworks
including SATs and GCSE examinations.
Student Name
Contents
Chemistry Basics Notes
2-5
Practice questions
6-15
Exam questions
16-27
Mark scheme
28-34
Inside atoms
Aims
There are about 100 elements. Each one is made up of one kind of atom. Scientists have
discovered that atoms are made from smaller particles called protons, neutrons and electrons.
In this activity you will check your knowledge of atoms and the particles in them.
Questions
Which particles are found in the nucleus of an atom? Highlight any correct answers.
protons
neutrons
electrons
Which particles orbit the nucleus? Highlight any correct answers.
protons
neutrons
electrons
Which atomic particle has a charge of +1? Highlight the correct answer.
proton
neutron
electron
Which atomic particle has no charge? Highlight the correct answer.
proton
neutron
electron
Which atomic particle has a charge of −1? Highlight the correct answer.
proton
neutron
electron
Two of the particles each have a mass of one atomic mass unit. The other has almost no mass.
Which one has almost no mass? Highlight the correct answer.
proton
neutron
electron
The number of protons that an element has determines what atoms it contains. For example, all
carbon atoms have six protons.
In any atom, which particle is present in the same number as the number of protons?
Highlight the correct answer.
neutron
electron
1 Why is there no overall charge on an atom?
..............................................................................................................................
..............................................................................................................................
Revision Questions,
Elements, Mixtures and Compounds
1. Copy and complete the following table
2. What is the smallest particle of an element called?
3. What contains only one type of atom and is found on the periodic table?
4. What contains two or more elements chemically combined?
5. What contains two or more chemicals together which are not chemically combined?
6. What do we call a chemical that contains a metal, carbon and oxygen only?
7. Give an example of the above.
8. Describe what is meant by a molecule?
9. What do we call the elements that react?
10. What are three signs that a chemical reaction has taken place?
11. What is meant by a displacement reaction?
12. Use the periodic table and give the name of the elements and the number of atoms in each of the
following chemicals.
I. (NH4)2SO4
III. H3PO4
V. Ca(OH)2
II. C6H12O6
IV. Na2CO3
VI. (NH4)2SO4
Atomic structure
Aims
In this worksheet you will learn about the structure of an atom.
The electrons in an atom are arranged in shells or energy levels. Each shell can only hold up to a
certain number of electrons. Is there a link between the way the electrons are arranged and where the
element is placed on the periodic table?
Look at this diagram of a calcium atom. Calcium has an atomic number of 20, which means each atom
has 20 electrons. The electrons fill the lowest energy level first. This is the shell nearest the nucleus.
Questions
Use the diagram above to complete these sentences:
The first shell can hold a maximum of ................. electrons.
The second shell can hold a maximum of .................. electrons.
The third shell can hold ..................... electrons.
Using a periodic table to find the atomic numbers, fill in the following sketch diagrams for these atoms.
Remember, you must fill up one shell before you start on the next.
Lithium
Number of electrons _____
9
Neon
Number of electrons _____
Magnesium
Number of electrons _____
Chlorine
Number of electrons _____
Complete this table and answer the question below:
Element
Number of shells
with electrons in
Row or period on
periodic table
Calcium
Lithium
Magnesium
Neon
Chlorine
What is the link between the number of shells with electrons in and the row or period the element
is in on the periodic table?
....................................................................................................................................
....................................................................................................................................
10
....................................................................................................................................
Lithium is in Group 1 of the periodic table, magnesium is in Group 2 and chlorine is in Group 7. Look
at your sketches. Is there a link between the group and the way the electrons are arranged?
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
Discussion
Chemical reactions are all about electrons. During a chemical reaction, atoms give, take or share
electrons to make themselves more stable. Having electronic structures like the noble gases in Group
0 is best.
Which of the elements on the previous page is likely to be very unreactive as a result of the way its
electrons are arranged? Are there any other atoms on the periodic table which are likely to behave in
the same way?
11
Inside compounds
Aims
A compound is made by joining two or more different elements together. It is important to understand
what compound names are telling us. You also need to be able to read chemical formulae accurately.
Rule
What it means
Find the metal first.
If there is a metallic element in a compound,
it goes first in the name.
Change the name of the nonmetal.
The non-metal in a compound forms the
second part of the name. The end of the
element name is changed to ‘ide’. For
example, chlorine becomes chloride.
Is there a metal + oxygen?
If the only non-metal element is oxygen, the
compound is an ‘oxide’.
What if there is a metal and two
non-metals?
You often get oxygen and another non-metal
in a compound. Use the name of the other
non-metal and change the end of the name to
‘ate’ to show there is oxygen there. For
example, a compound with chlorine and
oxygen is a ‘chlorate’.
Questions
Name the compound made from sodium and fluorine.
..............................................................................................................................
What compound is made from oxygen and zinc?
..............................................................................................................................
What compound is made in the reaction between bromine and potassium?
..............................................................................................................................
Marble is a rock that contains a compound made from the elements oxygen, calcium and carbon. What
is the compound called?
..............................................................................................................................
12
Copper sulfate forms bright blue crystals. The atoms of which elements would you find in copper
sulfate?
..............................................................................................................................
When you are reading chemical formulae, the different symbols tell you which types of atoms are in the
compound.
Small (subscript) numbers tell you how many atoms there are of the element written just before the
number. If there is no number after a symbol, there is one atom of that element.
For example, the formula of water is H2O. Its molecules are made from two atoms of hydrogen and one
atom of oxygen.
What atoms are present in a molecule of CO2? How many of each type are there?
..............................................................................................................................
..............................................................................................................................
What atoms are present in one formula unit of KNO3? How many of each type are there?
..............................................................................................................................
..............................................................................................................................
..............................................................................................................................
What atoms would you find in one formula unit of Na2CO3? How many of each type are there?
..............................................................................................................................
..............................................................................................................................
..............................................................................................................................
13
Fundamental ideas Test Yourself
1
Use numbers from the list to complete the table to show the charge on each subatomic
particle. (3)
+2 +1 0 –1 –2
Subatomic particle
Charge
electron
neutron
proton
2
Use the periodic table at the back of your book to help you to answer this question.
a
How many protons are in an atom of fluorine?
...................................................................................................................................
b
How many electrons are in an atom of carbon?
...................................................................................................................................
c
Complete the electronic structure of aluminium: 2,8, .......
d
What is the electronic structure of potassium?
...................................................................................................................................
3
(1)
(1)
(1)
(1)
Neon is a noble gas.
a
What does this tell you about its electronic structure?
...................................................................................................................................
b
(1)
Draw a diagram to show the electronic structure of neon.
(2)
14
4
a
Magnesium has the electronic structure 2,8,2. Explain, in terms of its electronic structure,
why magnesium is in Group 2 of the periodic table.
...................................................................................................................................
b
Give one way in which the electronic structures of the atoms of Group 2 elements are:
i
the same
...................................................................................................................................
ii
(1)
different.
...................................................................................................................................
c
(1)
(1)
When magnesium is heated in air it burns with a bright flame and produces magnesium
oxide.
Calcium is also in Group 2. Describe what you expect to happen and what would be
produced when calcium is heated in air.
...................................................................................................................................
...................................................................................................................................
5
(2)
Sodium reacts with water to produce sodium hydroxide and hydrogen.
The word equation for this reaction is:
sodium + water → sodium hydroxide + hydrogen
a
Name one substance in this equation that is:
i
an element
...................................................................................................................................
ii
(1)
a compound
...................................................................................................................................
(1)
iii has ionic bonds
...................................................................................................................................
(1)
iv has covalent bonds
15
...................................................................................................................................
b
(1)
If 2.3 g of sodium reacted with 1.8 g of water, what would be the total mass of sodium
hydroxide and hydrogen produced? Explain your answer.
...................................................................................................................................
...................................................................................................................................
c
Balance the symbol equation for this reaction.
...... Na + ...... H2O → ...... NaOH + H2
d
(2)
(1)
Lithium is in the same group of the periodic table as sodium.
i
Write a word equation for the reaction of lithium with water.
...................................................................................................................................
ii
(1)
What is the formula of lithium hydroxide?
...................................................................................................................................
(1)
iii How many atoms are shown in the formula of lithium hydroxide you have written?
...................................................................................................................................
(1)
16
Exam questions
Q1.
About 100 years ago a scientist called J. J. Thomson thought that an atom was a ball of
positive charge with negative particles stuck inside. Today a different model is used. The
diagram shows how an atom of carbon is represented by this model.
(a)
The negative particles
are called electrons.
(i)
What is the name of the positive particles
?
...........................................................................................................................
(1)
(ii)
What particle is represented by ●?
...........................................................................................................................
(1)
(iii)
What is the central part of the atom called that contains both
and ●?
...........................................................................................................................
(1)
(b)
Use the model to explain why the six electrons are arranged as shown.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(Total 5 marks)
2
Sando-K is a medicine. It is given to people whose bodies contain too little of a particular
element.
Sando-K is a mixture of two compounds. The formulae of the two compounds are given below.
KHCO3
KCl
17
(a)
Use the Data Sheet to help you to name all the elements in these compounds.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(3)
(b)
Which metal do people given Sando-K need?
.....................................................................................................................................
(1)
(Total 4 marks)
Q3.
(a)
The list below gives six substances.
•
aluminium
•
beer
•
copper
•
milk
•
pure water
•
sodium chloride
Put each substance in the correct column of the table.
ELEMENTS
COMPOUNDS
MIXTURES
(3)
(b)
Elements can be divided into two groups, metals and non-metals.
The list below gives some properties of elements.
•
brittle
•
can be hammered into shape
•
dull
•
good conductors of electricity
•
poor conductors of electricity
18
•
shiny
Put each property into the correct column.
PROPERTIES OF METALS
PROPERTIES OF NON-METALS
(3)
(Total 6 marks)
Q4.
There are millions of different substances that make up our world. All these substances are
made from chemical elements.
(a)
What is an element?
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(1)
(b)
Many substances are compounds. What is a compound?
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(Total 3 marks)
Q5.
John Dalton wrote these statements in 1808.
•
“All substances are made of a vast number of extremely small particles called atoms.”
•
“Every particle of water is like every other particle of water, every particle of hydrogen is
like every other particle of hydrogen, etc.”
19
(a)
“Every particle of water is like every other particle of water.” Use Dalton’s ideas and your
knowledge of water to explain why.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(b)
Dalton thought that all atoms of an element are exactly the same. We now know that it is
possible to have atoms of the same element but with different mass numbers.
The diagrams represent two atoms of hydrogen.
Atom A
Atom B
State, in terms of particles, how these two atoms are different.
.....................................................................................................................................
.....................................................................................................................................
(1)
(Total 3 marks)
Q6.
The diagram shows the structure of a lithium atom.
(a)
(i)
What is represented by
(ii)
What is represented by
.................................................................................
...........................................................................
(2)
20
(b)
What is the symbol for lithium? ................................................................................
(1)
(Total 3 marks)
Q7.
The diagrams show the electronic arrangement of the atoms of two elements.
(i)
Name the part of the atoms labelled X.
....................................................................................................................................
(1)
(ii)
Why are these two elements in the same group of the Periodic Table?
....................................................................................................................................
....................................................................................................................................
(1)
(Total 2 marks)
Q8.
Lithium metal is used in alkaline batteries.
(a)
The diagram shows the atoms in lithium metal.
Why is lithium metal described as an element?
.....................................................................................................................................
.....................................................................................................................................
(1)
21
(b)
The diagram below represents a lithium atom.
Choose words from the box to label parts of the atom.
bond
electron
molecule
nucleus
(2)
(Total 3 marks)
Q9.
(a)
Hydrogen is an element.
The diagram shows the parts of a hydrogen atom.
Use words from the box to label the diagram.
electron
group
nucleus
symbol
(2)
(b)
Hydrogen can be used as a clean fuel for cars.
22
(i)
When hydrogen burns in air, it reacts with another element.
Complete the word equation for this reaction.
hydrogen
→
+ .................................
water
(1)
(ii)
Suggest one reason why hydrogen is called a clean fuel.
.........................................................................................................................
.........................................................................................................................
(1)
(Total 4 marks)
Q10.
Atoms are made up of three main particles called protons, neutrons and electrons.
Use the periodic table on the data sheet to help you to answer these questions.
(a)
Sodium is in Group 1 of the periodic table.
(i)
Why are potassium and sodium in the same Group of the periodic table?
...............................................................................................................
...............................................................................................................
(1)
(ii)
How many protons are in an atom of sodium? .....................................
(1)
(iii)
The atomic number of sodium is 11.
How many neutrons are in an atom of sodium with mass number 23?
......................................
(1)
(iv)
Each sodium atom has 11 electrons. Complete the electronic structure of sodium.
(2)
(b)
The chemical equation for a reaction of sodium is shown below.
2Na + Cl2 → 2NaCl
23
Describe this reaction of sodium in terms of the names of the substances and the
numbers of the atoms involved.
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
(3)
(Total 8 marks)
Q11.
(a)
The chemical equation for a reaction of sodium is shown below.
2Na + Cl2 → 2NaCl
Describe this reaction of sodium in terms of the names of the substances and the
numbers of the atoms involved.
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
(3)
(b)
Use the periodic table on the data sheet to help you to answer this question.
(i)
Complete the electronic structure of sodium.
(2)
(ii)
How is the electronic structure of sodium different from the electronic structure of
chlorine?
24
...............................................................................................................
...............................................................................................................
(1)
(Total 6 marks)
Limestone has been called the Earth’s most useful rock.
Q12.
(a)
Limestone contains calcium carbonate, CaCO3.
(i)
Complete the table to show the number of atoms of each element in the formula of
calcium carbonate.
Calcium has been done for you.
Element
Number of atoms in the formula CaCO3
Calcium, Ca
1
Carbon, C
Oxygen, O
(2)
(ii)
The diagram below represents a carbon atom.
Use words from the box to label the parts of this atom.
bond
electron
molecule
nucleus
(2)
(b)
At a cement works, limestone is mixed with clay and
heated in a kiln.
25
Use the information in the diagram to answer these questions.
(i)
Name the fuel that is used to heat the limestone and clay.
...........................................................................................................................
(1)
(ii)
Limestone contains calcium carbonate, CaCO3.
Draw a ring around the correct gas in the box to complete the sentence.
argon.
The gas formed when calcium carbonate
decomposes is
carbon dioxide.
nitrogen.
(1)
(c)
The cement works starts to burn a different fuel.
Local residents are concerned because more children are suffering asthma attacks.
Residents have also noticed that parked cars are becoming dirty because of smoke
particles from the chimney.
The table shows the possible medical risk from smoke particles.
(i)
Particle size in mm
Medical effect
Larger than 0.4
No medical risks known
0.3 and smaller
Causes asthma attacks
0.2 and smaller
May cause cancer
Give two reasons why local residents are concerned about the cement works burning a different fuel.
1 ........................................................................................................................
...........................................................................................................................
2 ........................................................................................................................
...........................................................................................................................
(2)
(ii)
The company operating the cement works stated that smoke particles from the chimney had not
changed since it started burning the different fuel.
If you were a local resident, what evidence would you like to see to help you decide
if the company’s statement is true or not?
...........................................................................................................................
...........................................................................................................................
26
...........................................................................................................................
...........................................................................................................................
(2)
(Total 10 marks)
Q13.
Use the Periodic Table of Elements on the Data Sheet to help you to answer this
question.
(a)
Describe, in as much detail as you can, the structure of a fluorine atom.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(3)
(b)
Complete the diagram to show the electronic structure of a magnesium atom.
(1)
(Total 4 marks)
Q14.
Hot air balloons burn hydrocarbons to heat the air.
(a)
(i)
The hot air contains these gases: nitrogen, N2
oxygen, O2
argon, Ar
carbon dioxide, CO2
water vapour, H2O
Argon is an element.
What is an element?
....................................................................................
.......................................
27
...........................................................................................................................
(1)
(ii)
Name one other gas in the hot air that is also an element.
...........................................................................................................................
(1)
(b)
Propane, C3H8, can be represented as:
H
H
│
│
H
│
│
H
H
H
│
│
H
Use the correct words from the box to complete the sentences.
bond
(i)
carbon
compound
element
mixture
Propane is a ....................................... and is made up of atoms of hydrogen
and .......................................
(2)
(ii)
Each line between the atoms in propane represents a chemical .......................
(1)
(Total 5 marks)
28
Mark Scheme
M1.
(a)
(i)
proton
1
(ii)
neutron
1
(iii)
nucleus
1
(b)
there are shells or energy levels or orbitals
do not accept ring
1
the maximum number of electrons
found in the first shell or energy level is 2
accept first shell is full with 2 electrons
1
[5]
(a)
potassium, hydrogen,
carbon, oxygen,
chlorine or iodine
3 correct gains 1 mark
4 correct gains 2 marks
all correct gains 3 marks
(deduct 1 mark for each incorrect answer)
3
(b)
potassium (K)
for 1 mark
1
[4]
(a)
elements:
compounds:
mixture:
aluminium, copper,
pure water, sodium chloride,
beer, milk
2/3 correct gains 1 mark
4/5 correct gains 2 marks
all correct gains 3 marks
3
(b)
metals:
non metals:
can be hammered into shape,
good conductor of electricity, shiny
brittle, dull, poor conductors of electricity
2/3 correct gains 1 mark
4/5 correct gains 2 marks
all correct gains 3 marks
3
[6]
M4.
(a) a substance which contains one type of atom
or a substance that cannot be broken down
into anything simpler
for 1 mark
1
(b)
more than one element/more than one type of atom
combined/join together/bonded
for 1 mark each
2
[3]
29
M5.
(a) water (molecules) contain two hydrogen
atoms and one oxygen atom
all water molecules have the formula H2O for 2 marks
water molecules contain hydrogen and
oxygen (atoms) for 1 mark
water is H2O for 1 mark
2
(b)
atom A has no neutrons / atom B has one neutron
allow different numbers of neutrons
1
[3]
M6.
(a)
(i)
neutron (name only)
2
(ii)
nucleus / protons and neutrons
each for 1 mark
(do not allow mass number)
(b)
Li (correct cases of letters required)
for 1 mark
1
[3]
M7.
(i)
nucleus
1
(ii)
they both have seven electrons in the outer shell
accept they both have the same
number of electrons in the outer
shell
both need one electron to make full
outer shell
1
[2]
M8.
(a)
made of one sort of atom
accept it is in the periodic table
accept it only has lithium atoms
1
(b)
nucleus labelled correctly
1
electron labelled correctly
1
[3]
M9.
(a)
electron
words must be in correct position
1
nucleus
1
(b)
(i)
oxygen / O2
ignore air
1
(ii)
any one from:
•
(water) does not pollute
accept no harmful gas(es)
30
•
(only) water is produced
•
no carbon dioxide (is produced)
accept no greenhouse gas(es) / effect
•
no sulfur dioxide (is produced)
accept no acid rain
•
no nitrogen oxides (are produced)
•
no carbon / no particles (are produced)
1
[4]
M10.
(a)
(i)
both have one / 1 electron in the outer energy level / shell
allow both react in a similar way
1
(ii)
eleven / 11
1
(iii)
twelve / 12
1
(iv)
(2x)
max 1 if candidate changes the number of electrons in the first energy level / shell
8x (in second energy level / shell)
1
1x (in outer energy level / shell)
1
(b)
two sodium atoms (react)
1
two (bonded) chlorine atoms (react)
allow one chlorine molecule (reacts)
1
two sodium ions and two chloride ions (are produced)
allow two molecules of sodium chloride (are produced) or two sodium chloride particles (are
produced)
1
[8]
M11.
(a)
two sodium atoms (react)
1
two (bonded) chlorine atoms (react)
allow one chlorine molecule (reacts)
1
two sodium ions and two chloride ions (are produced)
allow two molecules of sodium chloride (are produced) or two sodium chloride particles
(produced)
1
(b)
(i)
(2x)
max 1 if candidate changes the number of electrons in the first energy level / shell
8x (in second energy level / shell)
1
1x (in outer energy level / shell)
1
31
(ii)
sodium has 1 electron in its outer energy level / shell
or
chlorine has 7 electrons in its outer energy level / shell
1
[6]
M12.
(a)
(i)
1
1
3
1
(ii)
nucleus
1
electron
1
(b)
(i)
methane / CH4
accept natural gas
ignore air
do not allow other gases
1
(ii)
carbon dioxide
1
(c)
(i)
any two from:
•
medical risks
•
asthma
•
cancer
•
dirt
•
causes global warming / global dimming / greenhouse effect / acid rain
ignore death
accept effect on health
accept difficulty breathing/ lung disease
allow smoke particles
allow harmful for the environment
2
(ii)
any two from:
•
have a test done / scientific evidence
•
independent (evidence)
•
comparison of smoke particles / when different
fuels used
•
medical evidence or more / less asthma attacks or
cancer or dirt on cars
2
[10]
M13.
(a)
9 protons /Proton Number 9
mass / atomic number is neutral
1
32
10 neutrons
1
electron arrangement 2,7 / 9 electrons
incorrect configurations neutral
if no points scored, allow 1 mark for nucleus surrounded by electrons or nucleus contains
neutrons and protons
1
(b)
Mark is for 2,8,2 arrangements.
accept electrons anywhere in correct orbit
1
[4]
M14.
(a)
(i)
made up of one sort of atom
accept it is in the periodic table
or
has its own symbol
1
(ii)
nitrogen / N / N2 or oxygen / O / O2
do not accept argon or helium
do not accept oxide
1
(b)
(i)
compound
1
carbon
1
(ii)
bond
1
[5]
Answers to worksheets
Inside the atom
Answers to questions
1
protons and neutrons
2
electrons
3
proton
4
neutron
5
electron
6
electron
7
electron
8
The charges on the protons and electrons cancel each other out if there is the same number of each.
Atomic structure
Answers to questions
The first shell can hold a maximum of 2 electrons.
The second shell can hold a maximum of 8 electrons.
The third shell can hold a maximum of 8 electrons.
33
Element
Number of shells with
electrons in
Row or period on periodic
table
Electron diagrams to
atoms:
Number of electrons:
in second, or 2,1)
Number of electrons:
Neon
electrons: 10 (2, 8)
Number of electrons:
Calcium
4
4
Lithium
2
2
Magnesium
3
3
Neon
2
2
Chlorine
3
3
represent these
Lithium
3 (2 in first shell, 1
Magnesium
12 (2, 8, 2)
Number of
Chlorine
17 (2, 8, 7)
The number of electrons in the outermost used shell is the same as the group number on the periodic table, e.g. chlorine is in Group 7
and has 7 electrons in the third shell. Elements in Group 0, where neon is found, have no space in the outermost used shell.
Discussion
Neon has a very stable electronic structure and is very unreactive as a result. All the elements in the final group in the periodic table (Group 0)
are similarly unreactive. The heavier noble gases have been made to form compounds but only under very extreme conditions. The elements
in Group 0 are useful precisely because they are unreactive. Argon is blown over welds as they are being made to exclude oxygen, which
would otherwise react with and corrode the metal.
Inside compounds
Aims
This worksheet is designed to focus students on the basic knowledge they should have of what compound names mean and how to read
chemical formulae.
Teaching notes
Students will need access to a periodic table to complete this worksheet.
Answers to questions
sodium fluoride. Do not accept anything else, for example, sodium fluorine or fluoride sodium.
zinc oxide
potassium bromide
calcium carbonate
copper, sulfur and oxygen
carbon and 2 oxygen atoms
1 potassium, 1 nitrogen and 3 oxygen atoms
2 sodium, 1 carbon and 3 oxygen atoms
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Fundamental ideas Test yourself Answers
Subatomic particle
electron
neutron
proton
Charge
–1
0
+1
1
a
b
c
d
9
6
2,8,3
2,8,8,1
2
a It is stable or it has 8 electrons in its outer energy level/shell (not it has a full shell).
b Two electrons (dots or crosses) on inner circle, 8 electrons on outer circle.
3a Two electrons in its highest energy level/outer shell.
b i Same number of electrons or 2 electrons in highest energy level/outer shell.
(accept same number of electrons in first energy level/shell)
ii Different number of energy levels/shells.
c burns (with a bright flame)
(produces) calcium oxide
4a i sodium or hydrogen
ii water or sodium hydroxide
iii sodium hydroxide
iv water or hydrogen
b 4.1 g
mass is conserved in reactions or mass of reactants = mass of products
c 2Na + 2H2O → 2NaOH + H2
d i lithium + water → lithium hydroxide + hydrogen
ii LiOH
iii 3 or error carried forward from answer to (ii)
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