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KS3 Science · Year 9Chapter 6 · The periodic table and bonding
Year 9 · Chapter 6

The periodic table and bonding

By the end of this chapter you will be able to

  • Describe Mendeleev’s periodic table, and how groups and periods show patterns
  • Draw electron arrangements for the first 20 elements and link them to the group
  • Explain ionic bonding by transfer, with ion charges and formulae
  • Explain covalent bonding by sharing, with simple molecules and their formulae
  • Explain how giant structures and metallic bonding account for melting point and conduction

You should already know

  • Atoms, elements and the periodic table (Year 8 Science, Chapter 7)
  • Chemical symbols and formulae (Year 7 and Year 8 Science)

Where this leads

  • Reactivity and the reactivity series in Chapter 7, which uses the metals in this table

National Curriculum for England, Key Stage 3 science, Year 9. Content: 9C1 development of the periodic table: Mendeleev, gaps and ordering; groups and periods; electron arrangement of the first 20 elements, 9C1 metals and non-metals; noble gases; transition metals; patterns in properties (deepens Year 8, Chapter 7), 9C2 ionic bonding by transfer of electrons (ions and charges); covalent bonding by sharing (simple molecules and formulae), 9C2 giant structures (sodium chloride lattice, diamond, graphite) and metallic bonding (basic), and how bonding explains melting point and electrical conductivity.

Exercise P  Do you remember?

1
FWhat is the chemical symbol for sodium? Write the symbol.
2
FWhat is the name of the particle in the nucleus of an atom that has no charge? Write the word.
3
FWhat is 4 x 6? Write the number.
4
FWhich word describes a substance made of only one type of atom? Write the word.
5
FHow many protons does an oxygen atom have? Write the number.
6.1

Mendeleev and the periodic table

Year 9
9C1: the principles underpinning the Mendeleev periodic table; groups and periods; metals and non-metals
Video lesson: Mendeleev and the periodic tableComing soon
Story. In 1869, the chemist Dmitri Mendeleev wrote the known elements on cards and arranged them. He saw a pattern that repeated, and left gaps where he thought undiscovered elements must belong. Later discoveries matched his predictions.

Mendeleev arranged the elements in order of their atomic mass, and placed elements with similar properties in the same group. The vertical columns are groups, and the horizontal rows are periods. Elements in the same group react in similar ways.

Most elements are metals, found on the left and in the middle. Non-metals are on the right. The noble gases form group 0, and the metals in the middle are the transition metals.

The first 20 elements (periods 1 to 4)HHeLiBeBCNOFNeNaMgAlSiPSClArKCablue: metals; orange: non-metals; green: metalloids (boron, silicon)
The first 20 elements arranged in periods and groups, with metals and non-metals shaded

Key ideas

  • Mendeleev ordered the elements and left gaps for undiscovered ones.
  • Groups are vertical columns with similar properties; periods are rows.
  • Metals are on the left and middle; non-metals are on the right.
  • Group 0 holds the noble gases, which are unreactive.
Worked example 6.1.1
Mendeleev left gaps in his table. What did the gaps show? Write the words.

Method. Think about what a gap means.

  1. Think. A gap is a place for an element that had not been found yet.
    not been found
  2. Name it. So the gaps showed undiscovered elements.
    undiscovered elements
  3. Write the answer.
    undiscovered elements

Check. Some predictions were later confirmed. ✓

Worked example 6.1.2
In the first 20 elements, which group has the noble gases? Write the number.

Method. Recall the group of noble gases.

  1. Recall. The noble gases are unreactive and form group 0.
    group 0
  2. Name it. So the noble gases are in group 0.
    0
  3. Write the answer.
    0

Check. Helium, neon and argon are noble gases. ✓

Worked example 6.1.3
Name the group 1 metal that is the second element in the first column. Write the word.

Method. Find the element in the first column.

  1. Look. Group 1 contains lithium, sodium and potassium.
    lithium, sodium, potassium
  2. Name it. The second element in group 1 is sodium.
    sodium
  3. Write the answer.
    sodium

Check. Lithium is first and potassium is third. ✓

Watch out

Watch out: Mendeleev ordered by atomic mass, and the modern table orders by atomic number. The idea of groups and periods is the same.

Exam tip

Exam tip. A period is a row across the table; a group is a column down the table.

Try it (with your teacher, or a grown-up at home). With your teacher, look at a copy of the periodic table. Circle the elements in group 1, then group 0. Write down one property of each group that you can see from the table. Do not heat or mix any of the chemicals.

Exercise 6A  Mendeleev and the periodic table

1
FWhat is the name of the vertical columns in the periodic table? Write the word.
2
FWhat is the name of the horizontal rows in the periodic table? Write the word.
3
FWhich elements are on the right of the periodic table: metals or non-metals? Write the word.
4
FWhich group holds the noble gases? Write the number.
5
FAre noble gases reactive or unreactive? Write the word.
6
FName the group 1 metal that is at the top of the list in the table. Write the word.
7
FWhich two elements are in group 7 of the first 20 elements? Write the symbols.
8
PSHow many periods are shown in the first 20 elements? Write the number.
9
PSHow many elements are in period 2 of the first 20 elements? Write the number.
10
PSMendeleev ordered the elements by atomic mass. The modern table orders them by atomic number. Which is the same as the number of protons? Write the word.
11
RExplain why elements in the same group react in similar ways. Write one sentence. Accept any sentence saying they have the same number of outer electrons.
12
RChallenge: explain why Mendeleev left gaps in his table. Accept any sentence saying the gaps kept elements with similar properties in the same group, so the pattern held.
6.2

Electron arrangements of the first 20 elements

Year 9
9C1: electron arrangement of the first 20 elements, linked to group and period
Video lesson: Electron arrangements of the first 20 elementsComing soon
Story. A chemist draws the arrangement of electrons in a sodium atom, and in a chlorine atom. She notices that sodium has one electron on the outside, and chlorine has seven. She asks: “How do these numbers help us predict how they react?”

Electrons are arranged in shells around the nucleus. The first shell holds up to 2 electrons, and the second and third shells hold up to 8 each in the first 20 elements. The number of electrons in the outer shell is linked to the group: group 1 atoms have 1 outer electron, and group 7 atoms have 7.

Atoms with a full outer shell, such as neon and argon, are very unreactive. Other atoms gain, lose or share electrons to get a full outer shell.

SymbolElementAtomic numberElectrons in each shell
Hhydrogen11
Ccarbon62, 4
Ooxygen82, 6
Nasodium112, 8, 1
Mgmagnesium122, 8, 2
Clchlorine172, 8, 7
Arargon182, 8, 8
Kpotassium192, 8, 8, 1
Cacalcium202, 8, 8, 2
Electron arrangement of some of the first 20 elements

Key ideas

  • Shell 1 holds 2 electrons; shells 2 and 3 hold up to 8 each (first 20 elements).
  • Total electrons equal the atomic number (the number of protons).
  • The outer shell gives the group: group 1 has 1, group 7 has 7.
  • A full outer shell makes an atom unreactive.
Worked example 6.2.1
Write the electron arrangement of sodium, atomic number 11. Write the numbers.

Method. Fill the shells, 2 then 8, then the rest.

  1. Fill. Shell 1 holds 2 electrons, shell 2 holds 8.
    2, 8
  2. Count. The remaining electrons are 11 - 2 - 8 = 1, in shell 3.
    11 - 10 = 1
  3. Write. So the arrangement is 2, 8, 1.
    2, 8, 1
  4. Write the answer.
    2, 8, 1

Check. The total is 11 electrons. ✓

Worked example 6.2.2
Which group is chlorine in, from its outer electrons? Write the number.

Method. Count the electrons in the outer shell.

  1. Count. Chlorine has 2, 8, 7, so 7 electrons in the outer shell.
    7 outer
  2. Name it. Seven outer electrons means group 7.
    group 7
  3. Write the answer.
    7

Check. Group 7 atoms have seven outer electrons. ✓

Worked example 6.2.3
Why is argon unreactive? Write the words.

Method. Look at its outer shell.

  1. Look. Argon has 2, 8, 8, so its outer shell is full.
    full outer shell
  2. Name it. A full outer shell makes it unreactive.
    unreactive
  3. Write the answer.
    full outer shell

Check. Noble gases have full outer shells. ✓

Watch out

Watch out: the number of electrons in an atom equals its atomic number, not its mass number.

Exam tip

Exam tip. Fill shell 1 first (2), then shell 2 (8), then shell 3 (up to 8). Check the total is the atomic number.

Try it (with your teacher, or a grown-up at home). With your teacher, use coloured counters on a paper template with circles for shells. Build sodium (2, 8, 1) and chlorine (2, 8, 7). Say which group each one belongs to, from its outer counters. This is a model, not a real atom.

Exercise 6B  Electron arrangements of the first 20 elements

1
FHow many electrons can the first shell hold? Write the number.
2
FHow many electrons can the second shell hold in the first 20 elements? Write the number.
3
FWrite the electron arrangement of carbon. Write the numbers, separated by commas.
4
FWrite the electron arrangement of oxygen. Write the numbers, separated by commas.
5
FHow many outer electrons does a magnesium atom have? Write the number.
6
FWhich group is sodium in? Write the number.
7
FWhich group is calcium in? Write the number.
8
PSWhat is the total number of electrons in an atom of potassium? Write the number.
9
PSWrite the electron arrangement of potassium. Write the numbers, separated by commas.
10
PSWhich element in the first 20 has the arrangement 2, 8, 7? Write the name.
11
RExplain why neon is unreactive. Write one sentence. Accept any sentence saying its outer shell is full with 8 electrons.
12
RChallenge: explain why sodium and potassium react in similar ways. Accept any sentence saying both have one electron in the outer shell.
6.3

Ionic bonding

Year 9
9C2: ionic bonding by transfer of electrons (ions and charges); formulae of ionic compounds
Video lesson: Ionic bondingComing soon
Story. A sodium atom and a chlorine atom meet. The sodium atom gives up its single outer electron, and the chlorine atom takes it. Both now have full outer shells, and they are held together by the attraction of their opposite charges.

In ionic bonding, electrons are transferred from a metal atom to a non-metal atom. The metal atom becomes a positive ion, and the non-metal becomes a negative ion. Opposite charges attract, and this attraction is the ionic bond.

Sodium loses one electron to form Na+. Chlorine gains one electron to form Cl-. The charges balance, so the formula is NaCl.

Sodium chloride: a giant lattice of ionsNa+Cl-Na+Cl-Na+Cl-Cl-Na+Cl-Na+Cl-Na+Na+Cl-Na+Cl-Na+Cl-Cl-Na+Cl-Na+Cl-Na+the ions are held in place by strong attraction
Sodium chloride: a giant lattice of alternating sodium and chloride ions

Key ideas

  • Ionic bonding: a metal transfers electrons to a non-metal.
  • Metal atoms become positive ions; non-metal atoms become negative ions.
  • Opposite charges attract, which is the ionic bond.
  • The formula balances the charges: NaCl, MgO, CaCl2.
Worked example 6.3.1
A sodium atom loses one electron. What charge does the sodium ion have? Write the sign and number.

Method. Think about the electron lost.

  1. Think. Losing one negative electron leaves one more proton than electrons.
    one more proton
  2. Name it. So the ion has a charge of +1.
    +1
  3. Write the answer.
    +1

Check. Sodium forms Na+. ✓

Worked example 6.3.2
Write the formula of magnesium oxide. Magnesium forms Mg2+ and oxygen forms O2-. Write the formula.

Method. Balance the charges.

  1. Balance. The charges are +2 and -2, which balance with one of each.
    +2 and -2
  2. Write. So the formula is one Mg and one O.
    MgO
  3. Write the answer.
    MgO

Check. The total charge is zero. ✓

Worked example 6.3.3
Write the formula of calcium chloride. Calcium forms Ca2+ and chlorine forms Cl-. Write the formula.

Method. Balance the charges.

  1. Balance. Ca is +2, so it needs two Cl- ions to balance.
    two Cl ions
  2. Write. So the formula is one Ca and two Cl.
    CaCl2
  3. Write the answer.
    CaCl2

Check. +2 and two -1 make zero. ✓

Watch out

Watch out: the metal is always the positive ion, and the non-metal the negative ion. Do not write Cl+.

Exam tip

Exam tip. Write the charges first, then choose the numbers of each ion so the total charge is zero.

Try it (with your teacher, or a grown-up at home). With your teacher, look at a model of sodium chloride, or a picture of the lattice. Count the sodium and chloride ions in a small block. Say how many of each you see, and why the ratio is one to one.

Exercise 6C  Ionic bonding

1
FIn ionic bonding, what is transferred between atoms? Write the word.
2
FDoes a metal atom gain or lose electrons in ionic bonding? Write the word.
3
FIs a chloride ion positive or negative? Write the word.
4
FWhat is the charge on a sodium ion? Write the sign and the number.
5
FWhat is the charge on a magnesium ion? Write the sign and the number.
6
FWhat is the name of the attraction between opposite charges in an ionic compound? Write the words.
7
FWrite the formula of sodium chloride. Write the formula.
8
PSWrite the formula of magnesium oxide. Write the formula.
9
PSWrite the formula of calcium chloride. Write the formula.
10
PSIn sodium chloride, how many chloride ions balance one sodium ion? Write the number.
11
RExplain why sodium chloride has a high melting point. Write one sentence. Accept any sentence saying strong attractions between ions in the lattice need a lot of energy to break.
12
RChallenge: explain why solid sodium chloride does not conduct electricity, but molten sodium chloride does. Accept any sentence saying the ions are fixed in the solid, but free to move when molten.
6.4

Covalent bonding and simple molecules

Year 9
9C2: covalent bonding by sharing (simple molecules and their formulae)
Video lesson: Covalent bonding and simple moleculesComing soon
Story. A pupil sees a water molecule drawn as a small picture. The oxygen atom is in the middle, with a hydrogen atom on each side. The teacher says the atoms share electrons, so that each has a full outer shell.

In covalent bonding, atoms share pairs of electrons. Each shared pair is one covalent bond. The atoms in a simple molecule are held together by covalent bonds, and the molecules are held apart by much weaker forces.

Hydrogen (H2) has one shared pair. Water (H2O) has two covalent bonds. Methane (CH4) has four. Carbon dioxide (CO2) has four shared pairs, in two double bonds.

OHHeach line is a shared pair of electronsH2O: 2 covalent bonds
Water molecule with two shared pairs of electrons between oxygen and hydrogen
MoleculeFormulaBonds
hydrogen, H2H21
water, H2OH2O2
methane, CH4CH44
carbon dioxide, CO2CO24
Simple molecules and the number of shared pairs (bonds) in each

Key ideas

  • Covalent bonding: atoms share pairs of electrons.
  • Simple molecules have weak forces between molecules, so low melting points.
  • Simple molecules do not conduct electricity, as they have no free charges.
  • The formula shows the atoms in a molecule, for example H2O.
Worked example 6.4.1
How many covalent bonds are in one water molecule, H2O? Write the number.

Method. Count the shared pairs.

  1. Count. The oxygen shares one pair with each hydrogen.
    one pair with each
  2. Total. So there are 2 shared pairs, which is 2 bonds.
    2
  3. Write the answer.
    2

Check. Two hydrogens, two bonds. ✓

Worked example 6.4.2
Write the formula of a methane molecule, which has one carbon atom and four hydrogen atoms. Write the formula.

Method. Count the atoms of each element.

  1. Count. One carbon and four hydrogen atoms.
    one C and four H
  2. Write. So the formula is CH4.
    CH4
  3. Write the answer.
    CH4

Check. Methane has four bonds. ✓

Worked example 6.4.3
Why does water have a low melting point? Write the words.

Method. Think about what breaks on melting.

  1. Think. Melting breaks the weak forces between molecules, not the covalent bonds.
    weak forces between molecules
  2. Conclude. Weak forces need little energy, so the melting point is low.
    little energy
  3. Write the answer.
    weak forces between molecules

Check. The covalent bonds inside the molecules stay intact. ✓

Watch out

Watch out: melting a simple molecular substance breaks the weak forces between molecules, not the covalent bonds inside them.

Exam tip

Exam tip. Write the formula by counting each atom, not each bond. Subscripts show how many of each atom.

Try it (with your teacher, or a grown-up at home). With your teacher, use drawing and modelling kits or paper: draw dots for the electrons in a hydrogen molecule (H2) and water (H2O). Show each shared pair with a line, and count the bonds.

Exercise 6D  Covalent bonding and simple molecules

1
FIn covalent bonding, what do atoms share? Write the word.
2
FHow many shared pairs are in a hydrogen molecule, H2? Write the number.
3
FHow many covalent bonds does a water molecule, H2O, have? Write the number.
4
FWhat is the formula of methane, which has one carbon and four hydrogen atoms? Write the formula.
5
FWhat is the formula of carbon dioxide? Write the formula.
6
FDo simple molecules conduct electricity? Write yes or no.
7
FIs the melting point of a simple molecular substance usually high or low? Write the word.
8
PSHow many hydrogen atoms are in one molecule of water? Write the number.
9
PSHow many atoms are in one molecule of carbon dioxide, CO2? Write the number.
10
PSA molecule of methane has how many shared pairs? Write the number.
11
RExplain why water has a low melting point even though its bonds are strong. Write one sentence. Accept any sentence saying melting breaks the weak forces between molecules, not the strong covalent bonds.
12
RChallenge: explain why a simple molecule like oxygen (O2) does not conduct electricity. Accept any sentence saying it has no free charged particles that can carry the current.
6.5

Giant structures and metallic bonding

Year 9
9C2: giant structures (diamond, graphite) and metallic bonding (basic); how bonding explains melting point and electrical conductivity
Video lesson: Giant structures and metallic bondingComing soon
Story. A jeweller and an engineer both use carbon. Diamond in a ring is very hard and does not carry electricity; graphite in a pencil is soft and does carry a current. Both are made of carbon, so the difference must come from how the atoms are bonded.

A giant covalent structure has millions of atoms joined by covalent bonds. In diamond, each carbon bonds to four others in a rigid lattice, so it is very hard with a very high melting point. In graphite, each carbon bonds to three others in flat layers. Each carbon has one electron that is free to move, so graphite conducts electricity.

In metallic bonding, metal atoms lose their outer electrons, which move freely through the metal. The positive metal ions are held together by these shared electrons. This explains why metals conduct electricity and can be bent without breaking.

SubstanceType of bondingMelting point and stateElectrical conduction
sodium chlorideionichigh, solidconducts when molten or dissolved
watercovalent (simple molecule)low, liquiddoes not conduct
diamondgiant covalentvery high, soliddoes not conduct
coppermetallichigh, solidconducts when solid
Four substances, their bonding, melting point and conduction

Key ideas

  • Diamond: each carbon bonds to four others; very hard, very high melting point, does not conduct.
  • Graphite: layers of carbon; each carbon has one free electron, so it conducts.
  • Metals: positive ions in a sea of free electrons; they conduct and can be bent.
  • Ionic compounds conduct only when molten or dissolved, when the ions can move.
Worked example 6.5.1
Diamond is a giant covalent structure. Name the number of other carbon atoms that each carbon is bonded to. Write the number.

Method. Recall the structure.

  1. Recall. Each carbon in diamond is covalently bonded to four others.
    four others
  2. Name it. So the number is 4.
    4
  3. Write the answer.
    4

Check. Four bonds make a rigid lattice. ✓

Worked example 6.5.2
Does graphite conduct electricity? Write yes or no.

Method. Recall the free electrons.

  1. Recall. Each carbon in graphite has one free electron, which can carry a current.
    free electron
  2. Decide. So graphite conducts electricity, and the answer is yes.
    yes
  3. Write the answer.
    yes

Check. Diamond does not, because all its electrons are fixed in bonds. ✓

Worked example 6.5.3
What is the name of the free electrons in a metal? Write the words.

Method. Recall the name.

  1. Recall. The outer electrons in a metal move freely through the metal.
    move freely
  2. Name it. These are called delocalised electrons.
    delocalised electrons
  3. Write the answer.
    delocalised electrons

Check. They carry electricity through the metal. ✓

Watch out

Watch out: diamond and graphite are both pure carbon, but their structures differ, so their properties differ.

Exam tip

Exam tip. Explain conduction with the word free or delocalised electrons, and explain a high melting point with strong bonds that need much energy to break.

Try it (with your teacher, or a grown-up at home). With your teacher, test a pencil lead (graphite) and a metal paper clip in a simple circuit with a low-voltage cell and a bulb. Do not use mains electricity. Say which one lets the current through, and why.

Exercise 6E  Giant structures and metallic bonding

1
FWhat is the name of a structure with millions of atoms joined by covalent bonds? Write the words.
2
FHow many other carbon atoms is each carbon in diamond bonded to? Write the number.
3
FHow many other carbon atoms is each carbon in graphite bonded to? Write the number.
4
FIs diamond hard or soft? Write the word.
5
FDo metals conduct electricity? Write yes or no.
6
FIn metallic bonding, what do the outer electrons become? Write the words.
7
PSDoes graphite conduct electricity? Write yes or no.
8
PSDoes diamond conduct electricity? Write yes or no.
9
PSWhich substance has the higher melting point: diamond or water? Write the word.
10
RWhy can a metal be bent without breaking? Write one sentence. Accept any sentence saying the layers of positive ions can slide over each other while the electrons keep them held together.
11
RChallenge: explain why graphite is soft, but diamond is very hard, even though both are carbon. Accept any sentence saying graphite’s layers slide over each other, while diamond’s rigid lattice of bonds does not.

Chapter summary

SkillMethod
Periodic tableMendeleev ordered by atomic mass and left gaps; groups share properties; periods are rows; noble gases are group 0.
Electron arrangementShell 1 holds 2; shells 2 and 3 hold up to 8; outer electrons give the group.
Ionic bondingElectrons are transferred from a metal to a non-metal, forming ions with opposite charges; formulae balance the charges.
Covalent bondingAtoms share pairs of electrons; simple molecules have low melting points and do not conduct.
Giant structuresDiamond: four bonds per carbon, very hard; graphite: layers, one free electron per carbon, conducts.
Metallic bondingPositive ions in a sea of delocalised electrons; metals conduct and can be bent.

Can you…?

  • I can describe Mendeleev’s table, groups and periods, and metals and non-metals
  • I can draw electron arrangements for the first 20 elements and link them to a group
  • I can explain ionic bonding by transfer, and write the formula of an ionic compound
  • I can explain covalent bonding, and write the formula of a simple molecule
  • I can explain melting point and conduction using giant structures and metallic bonding

Key terms

group
a vertical column in the periodic table, with elements of similar properties
period
a horizontal row in the periodic table
noble gas
an unreactive element in group 0, with a full outer shell
transition metal
a metal in the middle block of the periodic table
shell
a layer of electrons around the nucleus of an atom
ion
an atom or group of atoms with an electrical charge
ionic bond
the attraction between oppositely charged ions
covalent bond
the bond formed when atoms share a pair of electrons
molecule
a group of atoms held together by covalent bonds
giant structure
a structure with millions of atoms held together by bonds
lattice
a regular arrangement of particles in a solid
delocalised electron
an electron in a metal that is free to move through it

Exercise 6Z  Check-up

1
What is the name of the vertical columns in the periodic table? Write the word.
2
Write the electron arrangement of sodium. Write the numbers, separated by commas.
3
Which group is chlorine in? Write the number.
4
What is the charge on a sodium ion? Write the sign and the number.
5
Write the formula of magnesium oxide. Write the formula.
6
What is the formula of carbon dioxide? Write the formula.
7
How many covalent bonds does a methane molecule have? Write the number.
8
Are the free electrons in a metal delocalised? Write yes or no.
9
Does diamond conduct electricity? Write yes or no.
10
Explain why a simple molecule has a low melting point. Write one sentence. Accept any sentence saying the weak forces between molecules are broken on melting, which needs little energy.

Total 18 marks. Allow about 18 minutes.

Exercise 6X  Practice test questions

1
FName the group of the periodic table that contains the noble gases. Write the number.[1 mark]
2
FWrite the electron arrangement of chlorine. Write the numbers, separated by commas.[1 mark]
3
FWhat is the formula of sodium chloride? Write the formula.[1 mark]
4
FName the type of bonding in which electrons are shared between atoms. Write the words.[1 mark]
5
PSWrite the formula of calcium chloride. Write the formula.[2 marks]
6
RExplain why sodium chloride conducts electricity when it is molten, but not when it is solid. Write one sentence. Accept any sentence saying the ions are free to move when molten, but are fixed in the solid.[2 marks]
7
FDescribe the difference between a period and a group in the periodic table. Write one sentence. Accept any sentence saying a period is a row and a group is a column.[2 marks]
8
RExplain why diamond has a very high melting point. Write one sentence. Accept any sentence saying each carbon is joined to four others by strong covalent bonds, which need much energy to break.[2 marks]
9
PSGive the number of shared pairs in a molecule of water. Write the number, and explain in one sentence why oxygen forms this number. Accept any answer giving 2, with oxygen needing two more electrons to complete its outer shell.[3 marks]
10
RExplain how metallic bonding allows metals to conduct electricity. Write two sentences. Accept any answer saying the outer electrons are delocalised and move freely, carrying a current through the metal.[3 marks]
← Chapter 5: The solar system, gravity, day and yearChapter 7: Reactivity, displacement and electrolysis →

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