11. patterns in the periodic table v1.0

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• The atomic model has changed throughout the centuries, starting in 400 BC, when it looked like a billiard ball →


Who are these men?

In this lesson, we’ll learn about the men whose quests for knowledge about the fundamental nature of the universe helped define our views.


Democritus

• This is the Greek philosopher Democritus who began the search for a description of matter more than 2400 years ago.

He asked: Could matter be divided into smaller and smaller pieces forever, or was there a limit to the number of times a piece of matter could be divided?

400 BC


Atomos• His theory: Matter could not be

divided into smaller and smaller pieces forever, eventually the smallest possible piece would be obtained.

• This piece would be indivisible.

• He named the smallest piece of matter “atomos,” meaning “not to be cut.”


Atomos To Democritus, atoms

were small, hard particles that were all made of the same material but were different shapes and sizes.

Atoms were infinite in number, always moving and capable of joining together.


This theory was ignored and forgotten for more than 2000 years!


Why?

• The eminent philosophers of the time, Aristotle and Plato, had a more respected, (and ultimately wrong) theory.

Aristotle and Plato favored the earth, fire, air and water approach to the nature of matter. Their ideas held sway because of their eminence as philosophers. The atomos idea was buried for approximately 2000 years.


Dalton’s Model

• In the early 1800s, the English Chemist John Dalton performed a number of experiments that eventually led to the acceptance of the idea of atoms.


Dalton’s Theory

• He deduced that all elements are composed of atoms. Atoms are indivisible and indestructible particles.

• Atoms of the same element are exactly alike.

• Atoms of different elements are different.

• Compounds are formed by the joining of atoms of two or more elements.


.

• This theory became one of the foundations of modern chemistry.


Thomson’s Plum Pudding Model

• In 1897, the English scientist J.J. Thomson provided the first hint that an atom is made of even smaller particles.


Thomson Model• He proposed a model of the

atom that is sometimes called the “Plum Pudding” model.

• Atoms were made from a positively charged substance with negatively charged electrons scattered about, like raisins in a pudding.


Thomson Model

• Thomson studied the passage of an electric current through a gas.

• As the current passed through the gas, it gave off rays of negatively charged particles.


Thomson Model

• This surprised Thomson, because the atoms of the gas were uncharged. Where had the negative charges come from?

Where did they come from?


Thomson concluded that the negative charges came from within the atom.

A particle smaller than an atom had to exist.

The atom was divisible!Thomson called the negatively charged “corpuscles,” today known as electrons.

Since the gas was known to be neutral, having no charge, he reasoned that there must be positively charged particles in the atom.

But he could never find them.


Rutherford’s Gold Foil Experiment

• In 1908, the English physicist Ernest Rutherford was hard at work on an experiment that seemed to have little to do with unraveling the mysteries of the atomic structure.


• Rutherford’s experiment Involved firing a stream of tiny positively charged particles at a thin sheet of gold foil (2000 atoms thick)


Most of the positively charged “bullets” passed right through the gold atoms in the sheet of gold foil without changing course at all.Some of the positively charged “bullets,” however, did bounce away from the gold sheet as if they had hit something solid. He knew that positive charges repel positive charges.


• This could only mean that the gold atoms in the sheet were mostly open space. Atoms were not a pudding filled with a positively charged material.

• Rutherford concluded that an atom had a small, dense, positively charged center that repelled his positively charged “bullets.”

• He called the center of the atom the “nucleus”

• The nucleus is tiny compared to the atom as a whole.


Rutherford

• Rutherford reasoned that all of an atom’s positively charged particles were contained in the nucleus. The negatively charged particles were scattered outside the nucleus around the atom’s edge.


Bohr Model

• In 1913, the Danish scientist Niels Bohr proposed an improvement. In his model, he placed each electron in a specific energy level.


Bohr Model

• According to Bohr’s atomic model, electrons move in definite orbits around the nucleus, much like planets circle the sun. These orbits, or energy levels, are located at certain distances from the nucleus.


Wave Model


The Wave Model

• Today’s atomic model is based on the principles of wave mechanics.

• According to the theory of wave mechanics, electrons do not move about an atom in a definite path, like the planets around the sun.


The Wave Model

• In fact, it is impossible to determine the exact location of an electron. The probable location of an electron is based on how much energy the electron has.

• According to the modern atomic model, at atom has a small positively charged nucleus surrounded by a large region in which there are enough electrons to make an atom neutral.


Electron Cloud:

• A space in which electrons are likely to be found.

• Electrons whirl about the nucleus billions of times in one second

• They are not moving around in random patterns.

• Location of electrons depends upon how much energy the electron has.


Electron Cloud:

• Depending on their energy they are locked into a certain area in the cloud.

• Electrons with the lowest energy are found in the energy level closest to the nucleus

• Electrons with the highest energy are found in the outermost energy levels, farther from the nucleus.


IndivisibleIndivisible ElectronElectron NucleusNucleus OrbitOrbit Electron Electron CloudCloud

GreekGreek XX

DaltonDalton XX

ThomsonThomson XX

RutherfordRutherford XX XX

BohrBohr XX XX XX

WaveWave XX XX XX


What is the periodic table?

Mendeleev created the first modern periodic table. What does it show and why is it always in the same order?


What is an element?


Where were the elements made?

There are 92 naturally-occurring elements and about 15 artificially-produced elements.

Elements were originally made in stars. In the early stages of a star’s life, light elements, such as hydrogen and helium, are formed. These fused together to make heavier elements such as carbon. Some of the even heavier elements were produced deep within stars and were sent out into the Universe when the stars exploded.Most of the artificially-produced elements have only been made in nuclear reactors or particle accelerators.


What is the atomic number?

Every element has a unique atomic number. This is the number of protons in the nucleus of each atom.

What is the atomic number of this helium atom?

A neutral atom must have equal numbers of protons and electrons, so the atomic number of an element also gives the number of electrons.

Helium has 2 protons, so its atomic number is 2.

Atoms are neutrally charged, so what links atomic number and the number of electrons?

electron

proton

neutron


What are the properties of elements?

A property is any characteristic feature of a substance.

Properties of sodium include:

The chemical properties of an element are determined by its atomic number.

Are there any patterns in the properties of the elements?

highly reactive

solid but melts easily

feels light (low density).

Can you name any properties of the element sodium?

A property is any characteristic feature of a substance.


How was the periodic table developed?


How are the elements arranged?


The periodic table

Arranging all the elements by their atomic number and their properties led to the creation of…

…the periodic table

Fr Ra Ac Rf Db Sg Bh Hs Mt Ds Rg ? ? ? ? ? ? ?

Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn

Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe

K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr

Na Mg Al Si P S Cl Ar

Li Be B C N O F Ne

H He


Missing elements!In this periodic table the symbols are replaced by atomic numbers. Some of the numbers are missing – where?

87 88 89 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118

55 56 57 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86

37 38 39 40 41 42 43 44 45 46 47 38 49 50 51 52 53 54

19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

11 12 13 14 15 16 17 18

3 4 5 6 7 8 9 10

1 2Two more rows of elements fit here.

They are called the lanthanides and actinides.


The elements in the periodic table


Columns of elements

What are columns of elements called?groups1 2 43 5 6 07


Rows of elements

periodsWhat are rows of elements called?

1

2

3

4

5

6

7


Patterns: metals and non-metals

on the right (except hydrogen)

Where are these different types of elements grouped together in the periodic table?

metals

non-metals

between metals and non-metalssemi-metals

on the left and centre

Can you name a semi-metal element?

Semi-metals have some properties similar to metals and other properties similar to non-metals.


Metals to non-metals, solids to gases


Patterns: reactivity of metals

Fr Ra Ac Rf Db Sg Bh Hs Mt Ds Rg

Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po

Rb Sr Y Zr NbMo Tc Ru Rh Pd Ag Cd In Sn

K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga

Na Mg Al

Li Be

What happens to the reactivity of metals down a group?Which is the most reactive metal?

increase in reactivity

incr

ease

in re

activ

ityWhat happens to the reactivity of metals along a period?


Which metal is more reactive?


Patterns: reactivity of non-metals

increase in reactivity

Group 0 elements are the most unreactive of all elements.

For the remaining non-metals and semi-metals, reactivity increases up a group and along a period from left to right.

Which is the most reactive non-metal/semi-metal?

At Rn

Sb Te I Xe

Ge As Se Br Kr

Si P S Cl Ar

B C N O F Ne

He

incr

ease

in re

activ

ity

unreactive


Which non-metal is more reactive?


Patterns, atomic number and electrons

What links atomic number and the properties of elements?

The periodic table shows that patterns in the properties of elements are linked to atomic number.

atomic number = number of protons

atomic number = number of electrons

number of protons = number of electrons

Electrons!

As atomic number increases by one, the number of electrons also increases by one.

This means that the elements in the periodic table are also arranged in order of the number of electrons.


How are electrons arranged?

Electrons are arranged in shells around an atom’s nucleus. (The shells can also be called energy levels).

This electron arrangement is written as 2,8,8.

1st shell holdsa maximum of

2 electrons

2nd shell holdsa maximum of

8 electrons

3rd shell holdsa maximum of

8 electrons

Each shell has a maximum number of electrons that it can hold. Electrons will fill the shells nearest the nucleus first.


Electron trends in the periodic table

Trends down a group:

The point at which a new period starts is the point at which electrons begin to fill a new shell.

The number of a group is the same as the number of electrons in the outer shell of elements in that group,except for group 0.

the number of outer shell electrons is the same; the number of complete electron shells increases by one.

the number of outer shell electrons increases by one;Trends across a period:

the number of complete electron shells stays the same.


Periodic table and electron structure


Electrons and groups


Groups and periods


What’s the electron arrangement?


Names of groups in the periodic table


Trends in group 1 (Alkali metals)

Element Atomic number

Mass number Melting point / C⁰

Boiling point / C ⁰

Li 3 7 180 1360

Na 11 23 93 900

K 19 39 63 777

- The elements in group 1 are called the alkali metals. They belong to the left-hand column in the periodic table.

-They are very reactive and must be stored in oil to avoid contact with air or water.

-The alkali metals all have low melting points and boiling points compared to other metals. The melting points and boiling points decrease as you go down the group.


Trends in group 7 (THE HALOGENS)

The halogens have low melting points and low boiling points. This is a typical property of non-metals. Fluorine has the lowest melting and boiling points. The melting and boiling points then increase as you go down the group.


Trends in group 0 (noble gases)

Element Atomic number

Electronic structure

Mass number

Melting point / C⁰

Boiling point / C ⁰

He 2 2 4 -270 - 269

Ne 10 2, 8 20 -249 - 246

Ar 18 2, 8, 8 40 -189 - 186

- Includes the elements helium, neon and argon.

- They are all gases and most are inert (unreactive) and do not form compounds. They are called noble gases.


Metals and their reaction with oxygen

Metals react with oxygen in the air to produce metal oxides.

For example, magnesium reacts with oxygen to produce magnesium oxide when it is heated in air:

Magnesium + oxygen → Magnesium oxide


Reaction of group 1 metals with oxygen• When pieces of Lithium, Sodium or potassium are take out of

their containers they are dull.

• When they are cut, the surface is shiny.

• They shiny surface soon becomes dull because the metal reacts with the oxygen in the air (without heating)

• The surface is now covered with the metal oxide.

• Metal + oxygen → Metal oxide


Reaction of metals with water• All the alkali metals react vigorously with cold water.

• In each reaction, hydrogen gas is given off and the metal hydroxide is produced.

• The speed and violence of the reaction increases as you go down the group. This shows that the reactivity of the alkali metals increases as you go down Group 1.

• Metal + water → Metal hydroxide + hydrogen

• Group 1 metals react vigorously with water.


• Other metals like calcium and magnesium react much slower.

• The gas (hydrogen) produced can be collected by displacement of water (apparatus shown below).

• The gas can then be tested to prove it is hydrogen with a lit splint (a pop sound is heard)


• Magnesium will react faster with steam than water (heated)

• Magnesium oxide and hydrogen are formed.


Reaction of metals with dilute acid• Magnesium will react with dilute hydrochloric acid to give a

salt and hydrogen

• Magnesium + Hydrochloric acid → Magnesium chloride+ hydrogen

• In your copybook• Write the word equation for the reaction of the following:(a)Magnesium and sulphuric acid(b)Zinc and nitric acid(c)Calcium and hydrochloric acid


The reactivity series• In a reactivity series, the most reactive element is placed

at the top and the least reactive element at the bottom.

• More reactive metals have a greater tendency to lose electrons.


Mnemonic to help you remember the reactivity series:

"Please Sam send Caught Monkeys And Zebras In Lead Cage with Security Guards."

1. Potassium - K2. Sodium - Na3. Calcium - Ca4. Magnesium - Mg5. Aluminium - Al6. Zinc - Zn7. Iron - Fe8. Lead - Pb9. Copper - Cu10. Silver - Ag11. Gold - Au


Metal Reaction with oxygen Reaction with water Reaction with acid

Potassium Burns brightly when heated to form an oxide.

Very vigorous reaction in cold water. The hydroxide is formed.

Violent reaction and very dangerous.

Sodium

Calcium Burns brightly in air when heated to form an oxide.

Slow reaction in cold water to form the hydroxide.

Magnesium Reaction, which becomes less vigorous as you go down the list.

AluminiumSlow reaction when heated to form an oxide.

Reacts with steam but not water to form an oxide.

Zinc

Iron

Lead No reaction with steam or water.

Copper No reaction.

Silver No reaction.

Gold


Displacement reactions• A more reactive metal will displace a less reactive metal

from a compound.

• More reactive metals have a greater tendency to lose electrons.

• A more reactive metal will displace a less reactive metal from a solution of one of its salts. For example:

magnesium + copper sulfate → copper + magnesium sulfate


Using Displacement reactionsThermite Welding

•A mixture of Aluminium and Iron oxide reacts to produce molten iron that is used to join railway rails together.

•Aluminium + Iron oxide → Aluminium oxide + Iron

•Aluminium replaces (displaces Iron) in Iron oxide to form Aluminium oxide.


Extraction of metals

Most metals are found as compounds. These compounds in the mining industry are called ores.

Ores are usually oxides, carbonates or sulphides of the metal, mixed with sandy impurities.

Some metals can be extracted from their ores by displacement reactions.

For example, iron can be extracted from its ore, haematite, (iron oxide) by heating with carbon at high temperatures. An industrial scale of extraction of iron is done in a giant blast furnace.

Iron oxide + carbon → iron + carbon dioxide


1. Potassium - K2. Sodium - Na3. Calcium - Ca4. Magnesium - Mg5. Aluminium - Al6. Zinc - Zn7. Iron - Fe8. Lead - Pb9. Copper - Cu10. Silver - Ag11. Gold - Au

Carbon can displace elements below Aluminium

Hydrogen can displace elements below Lead

Please Stop Calling Me A Cute Zebra I Like Her Call Smart Goat


What is a salt?


• Many methods for making salts start with acids.

• The table below gives the formulae of the three common acids that we can find in the laboratory.

Acids and salts

Name of acid Salts formed from the acidHydrochloric acid Chloride

Sulphuric acid Sulphate

Nitric acid Nitrate

Carbonic acid (CO₂ +H₂O) Carbonate

Citric acid (citrus fruits) Citrate


• Reaction of metals with dilute acids produces a salt.

Metal + acid → Salt + Hydrogen

• Example:

Zinc + hydrochloric acid → Zinc chloride + hydrogen

• In your copybook write the word equations for:(a)Magnesium with Nitric acid(b)Zinc with Nitric acid(c)Zinc with sulphuric acid(d)Aluminium with Hydrochloric acid

Preparing salts using Acids and metal


• Some metals do not react with metals (copper, gold and silver). They cannot displace hydrogen in the acid.

• So we use their metal oxides instead.

Metal oxide + acid → Salt + Water• Example:

Copper oxide + hydrochloric acid → Copper chloride + water

• In your copybook write the word equations for:(a)Silver with Nitric acid(b)Copper with Nitric acid(c)Copper with sulphuric acid(d)Silver with sulphuric acid

Preparing salts using Acids and metal oxide


• Some metals react with carbonic acid• So we use their metal oxides instead.

carbonate + acid → Salt + Water + Carbon dioxide• Example:

Calcium carbonate + hydrochloric acid →Calcium chloride + water + carbon dioxide

• In your copybook write the word equations for:(a)Calcium carbonate with Nitric acid(b)Calcium carbonate with sulphuric acid(c)Copper carbonate with Hydrochloric acid

Preparing salts using Acids and metal carbonates


• Some metals react with carbonic acid• So we use their metal oxides instead.

carbonate + acid → Salt + Water + Carbon dioxide• Example:

Calcium carbonate + hydrochloric acid →Calcium chloride + water + carbon dioxide

• In your copybook write the word equations for:(a)Calcium carbonate with Nitric acid(b)Calcium carbonate with sulphuric acid(c)Copper carbonate with Hydrochloric acid(d)Copper carbonate with Nitric acid

Preparing salts using Acids and metal carbonates


• When an acid is neutralized by an alkali, a salt is produced.Acid + Alkali → Salt + water

• Example:

Sodium hydroxide + hydrochloric acid → Sodium chloride + water

• In your copybook write the word equations for:(a)Calcium Hydroxide with Nitric acid(b)Lead Hydroxide with sulphuric acid(c)Magnesium Hydroxide with Hydrochloric acid(d)Iron Hydroxide with Nitric acid

Forming salts by neutralisation


• When soluble metal oxides dissolve in water.

• Example:

Sodium oxide + water→ Sodium hydroxide

• Sodium oxide is a base. Sodium hydroxide is an alkali.

Alkalis and bases

11. patterns in the periodic table v1.0

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