group 1 - alkali metals -...

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Group 1 – Alkali Metals


Fr Ra Ac Rf Db Sg Bh Hs Mt Ds Rg Cn Uut Fl Uup Lv Uus Uuo

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

Columns of elements

4groups 3 5 6 072

In the periodic table, the elements are arranged by their

properties and the number of protons they contain.

The vertical columns in the table are called groups.

1


Where are the alkali metals?

Elements in the same group in the periodic table have very

similar properties.

This is because all elements in a single group have the

same number of electrons in their outer shell, causing them

to react in a similar manner.


The alkali metals are very reactive and are rarely found in

nature as pure elements. To keep them from reacting with

oxygen in the air, pure alkali metals are often stored in oil.

The alkali metals can react

with water to form alkaline

compounds. This is why they

are called alkali metals.

Alkali metals are soft enough

to be cut with a knife.

Introducing the alkali metals

Alkali metals have low density.

Lithium, sodium and potassium all float on water.


The alkali metals all have one electron in their outer shell.

They are found in group 1

of the periodic table.

They have similar

physical and chemical

properties.

This means that:

They can readily lose

the outer shell electron

to form positive ions

with a +1 charge.

Electron structure


Bonding in alkali metals

sea of electrons

metal ions

Like other metals, the particles in

alkali metals are held together by

metallic bonds.

The metal atoms lose their outer

shell electrons to become

positive ions.

These electrons are delocalised,

and are free to move through the

structure, creating a ‘sea of electrons’.

The positively charged metal ions

are attracted to the sea of electrons.

This strong attraction is known as metallic bonding.


Identifying alkali metals


What are the properties of alkali metals?

They are shiny. This is only seen

when alkali metals are freshly cut.

They are good conductors of

heat and electricity.

They are soft and can be cut by a knife. Softness increases

going down the group.

They have a low density.

They have low melting and boiling points compared to

other metals.

These properties make the alkali metals different to typical

metals. However, alkali metals do share some properties of

typical metals:

Properties of alkali metals


What are the trends in density?


What is the trend in density?

The alkali metals generally become more dense going down

the group. The trend is not perfect because potassium is less

dense than sodium.

Element Density (g/dm3)

lithium

potassium

sodium

rubidium

caesium

0.53

0.97

0.86

1.53

1.87

Water has a density of 1g/dm³. Using this information,

which metals in group 1 can float on water?


What are the trends in melting point?


What are the trends in boiling point?


The melting and boiling points of alkali metals decrease

down the group.

element melting point (°C)

lithium

potassium

sodium

rubidium

caesium

181

98

64

39

28

boiling point (°C)

As the atoms get larger, the attraction between the positive

metal ions and the delocalised sea of electrons gets weaker.

This means the metals become easier to melt and boil.

1342

883

760

686

671

Melting and boiling points


Properties of alkali metals quiz


The reactivity of alkali metals increases going down the group.

The atoms of each element get

larger going down the group.

This means that the outer shell

electron gets further away from

the nucleus.

The further an electron is from the

positive nucleus, the easier it can

be lost in reactions.

This is why the reactivity of the alkali

metals increases going down group 1.

How does electron structure affect reactivity?

Why is this?


What is the order of reactivity?


All alkali metals react with the

oxygen in air to form metal oxides.

This produces a layer of dull oxide

on the surface of the metal.

The speed at which alkali metals

react with oxygen increases going

down the group.

How do alkali metals react with oxygen?

The type of reaction is called an oxidation reaction. When

an oxidation reaction takes place in alkali metals, the atom’s outer electron is lost.


Write a balanced symbol equation to show the formation of

a sodium oxide through an oxidation reaction:

The word equation for the oxidation reaction between an

alkali metal and oxygen is:

Write a balanced symbol equation to show the formation of

a lithium oxide through an oxidation reaction:

Oxidation equation


Ionic equation

Write the ionic equation for the oxidation of a sodium atom.

What is happening in this equation?

The sodium atom loses one

electron (e-) to form a positive

ion with a charge of +1.

Because oxidation is the loss of electrons, we say the

sodium atom has been oxidised.


All of the alkali metals react vigorously with water.

The reaction produces a gas that

ignites a lighted splint with a

squeaky pop. What is this gas?

It is an exothermic reaction as it releases a lot of heat.

When green universal indicator

is added to the reaction mixture,

it turns purple.

The reaction becomes more vigorous as you go down

the group.

How do alkali metals react with water?

What does this tell you about

the products of this reaction?

lithium


This reaction creates hydroxide (OH–) ions. Hydroxide ions

are alkaline.

The general equation for the reaction between an alkali

metal reacting with water is:

This is another reason why the group 1 elements are called

the alkali metals.

Water reaction equation


How does lithium react with water?

Lithium is the least reactive

of the alkali metals.

When added to water, it

fizzes and moves around

slowly across the surface

of the water.

What is the equation for this reaction? lithium


How does sodium react with water?

Sodium is more reactive than lithium. When it is added to

water, sodium fizzes and moves quickly across the surface.

What is the equation for this reaction?

The hydrogen sometimes catches fire

because of the heat from the reaction.

The sodium melts as it reacts

and becomes spherical and

shiny, like a ball bearing. sodium


Potassium is even more reactive than sodium. When

added to water, it moves across the surface very quickly.

Like sodium, potassium melts with

the heat of the reaction.

The reaction produces so much

heat that the hydrogen catches fire.

What colour would the flame be?

How does potassium react with water?

What is the equation for this reaction?

potassium


How will rubidium and caesium react with water?

How do alkali metals react with water?


Reacting with water


Alkali metals and chlorine react to form colourless,

crystalline salts called metal chlorides.

What are the word and chemical equations for the reaction

that produces sodium chloride?

The word and chemical equations for the reaction between

lithium and chlorine are:

How do alkali metals react with chlorine?


True or false?


Products of alkali metal reactions


Comparing reactivity with water


Glossary


Multiple-choice quiz

group 1 - alkali metals -...

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