Group 1 The Alkali Metals of the Periodic Table

Chemistry notes on the physical properties of lithium, sodium, potassium, rubidium, caesium (cesium) and francium, The chemical properties, chemical reactions with water, oxygen and chlorine - word equations & balanced equations and uses of the elements and compounds of the Group 1 Alkali Metals of the Periodic Table e.g. lithium, sodium & potassium etc. Also covered are explaining the group I alkali metal reactivity trend, uses of the alkali metals and alkali metal compounds.

Keywords-Links for this page: boiling points * chlorides * data on elements * density * electron arrangements * explaining reactivity trend * hydroxides * melting points * oxides * reaction with oxygen/chlorine * reaction with water * trends * typical properties * untypical properties  * uses

PLEASE NOTE A Level Students GCE Notes on s-block Gp 1 Alkali Metals & Gp2 Alkaline Earth Metals

Where are the Group 1 Alkali Metals in the Periodic Table?

The Group I Alkali Metals are the first vertical column on the left of the Periodic Table where you find most of the metallic elements. Therefore the Alkali Metal is the first element on the period from period 2 onwards.

Only the top portion of the periodic table is shown and remember metals tend to be on the left and also in the first vertical column, the Group 1 Alkali Metals there are also the elements caesium/cesium (Cs) and radioactive francium (Fr) below rubidium, but not shown.

Note: Using 0 to denote the Group number of Noble Gases is very historic now, since, compounds of xenon are known exhibiting a valency of 8. Because of the horizontal series of elements e.g. like the Sc to Zn block (10 elements), Groups 3 to 0 can also be numbered as Groups 13 to 18 to fit in with the actual number of vertical columns of elements. This can make things confusing, but there it is, classification is still in progress!

Introduction to the Group 1 Alkali Metals  (see also data table below)

The Alkali Metals form Group 1 of The Periodic Table, and called so because they form oxides and hydroxides that dissolve in water to give alkaline solutions.

They form the first element of a period, with one outer electron, in any period from period 2 onwards. This outer electron similarity makes them behave in a chemically similar way. Some of their physical properties are typical of metals and some are not so typical of metals. Although they all have one outer electron and so similar physical and chemical properties, a characteristic of a periodic table group, BUT always watch out for trends down a group too. Overview of Periodic Table

Why are the group 1 alkali metals like lithium, sodium and potassium store under oil? They are so reactive that they must be stored under oil in a well sealed glass container to minimise reaction with the oxygen or water vapour in air.

Note: Oil is a water repellent and a physical barrier towards air and moisture BUT the alkali metals still gradually corrode as traces of oxygen and water diffuse through the oil to reach the very reactive lumps of alkali metal!

In what ways are the group 1 alkali metals like lithium, sodium and potassium typical metals? Typical metallic properties: good conductors of heat and electricity, high boiling points, silvery grey surface (but rapidly tarnished by air oxidation).

When an alkali metal atoms reacts, it loses an electron (oxidation) to form a singly positively charged ion eg Na ==> Na⁺ + e^-. In terms of electrons 2.8.1 ==> 2.8 and so forming a stable ion with a noble gas electron arrangement.

They tend to readily react with most non-metals to form ionic compounds which are usually soluble white solids.

In what ways are the group 1 alkali metals like lithium, sodium and potassium not typical metals? Untypical metallic properties: low melting points, low density (first three float on water), very soft (easily squashed or cut with a knife, extremely malleable) and so they have little material strength.

Important trends down Group 1 with increase in atomic number (proton number), for the Alkali Metals ...

What are the group trends in melting point, boiling point, reactivity, size of atom (atomic radius), density and physical strength as you go down the group 1 alkali metals as the atomic/proton number increases?

the melting point and boiling point generally decrease down Group 1 (see data table below)

the element gets more reactive down Group 1 with increase in atomic number (explanation)

the atoms get bigger down Group 1 (as more electron shells are added, see data table below)

generally the density increases down Group 1 (see data table below), although the atom gets bigger, there is a greater proportional increase in the atomic mass (see data table).

generally the hardness decreases down Group 1

* For advanced AS level:  The bonding in metals involves the attraction between free negative electrons moving between positively ionised metal atoms (M⁺ ions). As the atomic radius increases the charges (positive nucleus and delocalised electrons) are further apart and the electrical attractive force is reduced. This weaker bonding results in a weaker-softer structure with a lower melting/boiling point.

A Level Chemistry AS-A2 Notes on s-block Gp 1 Alkali Metals & Gp2 Alkaline Earth Metals

There are element/compound identification details on the Chemical Tests page (use the alphabetical list at the top).

When heated strongly in a flame, the metals or their compounds give bright colours. Lithium - red/crimson, sodium - yellow, potassium - lilac/purple, rubidium red, caesium - blue and they can be used as a simple identification test - Flame Tests for Alkali Metals

Chemical symbol, name

(1nm = 10^-9m, 1pm = 10^-12m, nm x 1000 = pm or nm = pm/1000)

The Reaction of Alkali Metals with cold water

What is formed when group 1 alkali metals like lithium, sodium or potassium react with water? What do you see when the reaction takes place? Observations!

The Group 1 Alkali Metals are very reactive towards cold water.

The reaction with water is very exothermic, fast and violent.

If a lump of lithium, sodium or potassium is placed in cold water, the metal floats, it may melt and move around the surface of the water with 'fizzing'. Note that these alkali metals float on water because of their low density.

If universal indicator is added, it changes from green (pH 7)  to purple (pH 13-14), showing an alkaline metal hydroxide was formed.

The formation of an alkali with water is why they are called Alkali Metals.

The colourless gas hydrogen is also given off  and pops with lit splint - but this is not the best of experiments to collect it from!

The more reactive the metal, the more vigorous the reaction.

Lithium and sodium do not normally cause a flame but the potassium reaction is exothermic enough to ignite the hydrogen.

hydrogen + oxygen ==> water   (word equation)

2H₂ + O₂ =>  2H₂O

2H₂(g) + O₂(g) =>  2H₂O(l)   (symbol equation with state symbols)

The hydrogen flame turns lilac due to hot potassium atoms in it.

Note 1: In flame tests hot lithium atoms give a  crimson colour and sodium a yellow colour (more details).

Note 2: State symbols in equations: (g) = gas, (l) = liquid, (s) = solid, (aq) = aqueous solution in water

Rubidium, caesium and francium are very explosive with water.

Down the group the reaction gets faster and more violent as the metal gets more reactive

i.e. Li < Na < K < Rb < Cs < Fr or francium > caesium > rubidium > potassium > sodium > lithium

The reaction equation for sodium is in words and symbols ...

sodium + water ==> sodium hydroxide + hydrogen    (word equation)

2Na + 2H₂O ==> 2NaOH + H₂

2Na(s) + 2H₂O(l) ==> 2NaOH(aq) + H₂(g)   (symbol equation with state symbols)

and the equations are similar for any of the other Alkali Metals since they are in the same group of the Periodic Table, they behave chemically in the same way i.e. just substitute Li (lithium), K (potassium), Rb (rubidium), Cs (rubidium) or Fr (francium) for Na. Its handy to know the 'pattern' of both the word equations and symbol equations and it fits in with the idea, an important concept, that elements in the same group of vertical column in the periodic table, all tend to behave chemically in the same way - this is what the Periodic Table is all about!.

e.g.

potassium + water ==> potassium hydroxide + hydrogen    (word equation)

2K + 2H₂O ==> 2KOH + H₂

2K(s) + 2H₂O(l) ==> 2KOH(aq) + H₂(g)   (symbol equation with state symbols)

and

lithium + water ==> lithium hydroxide + hydrogen   (word equation)

2Li + 2H₂O ==> 2LiOH + H₂

2Li(s) + 2H₂O(l) ==> 2LiOH(aq) + H₂(g)   (symbol equation with state symbols)

You can write similar word or symbol equations for rubidium and caesium

Theoretically Francium is the most reactive and therefore the most explosive metal when in contact with water, however, it is also very radioactive and so the experiment is highly unlikely to be performed!

See also the GCSE/IGCSE Reactivity of Metals Notes for the reactivity of other metals compared to these Group 1 Alkali Metals.

sodium Na

Used as a heat transfer coolant in certain nuclear reactors because of its excellent heat conduction properties. The energized vapour is an orange-yellow and used in street lamps.

sodium Na⁺ salts

Common salt from sea water or underground deposits is sodium chloride, NaCl, and is the raw material for making sodium, hydrogen, chlorine and sodium chloride by electrolysis (see Group 7 Halogens notes).

'Soluble Aspirin' is the sodium salt of an organic acid. Salts of solid organic acids are usually more soluble than the acid itself. 

Sodium hydrogen carbonate  NaHCO₃

Sodium hydrogencarbonate's old name is sodium bicarbonate, often referred to as 'bicarb', is used in baking soda, pharmaceutical products like indigestion tablets and fire extinguishers. 

Sodium hydroxide NaOH

An industrially important alkali used in the manufacture of soaps, detergents, salts of acids (see Aspirin above), paper and ceramics.

For more on uses of metals see Transition Metals and Extra Industrial Chemistry

WHERE-WHAT NEXT?

• GCSE/IGCSE Multi-word fill exercise on Alkali Metals
• Flame Tests for Alkali Metals
• GCSE/IGCSE Summary of the Periodic Table
• GCSE/IGCSE Transition Metals Notes
• Alkali Metals GCSE/IGCSE multiple choice question Quiz - easier Foundation tier
• Alkali Metals GCSE/IGCSE multiple choice question Quiz - harder Higher tier

PLEASE NOTE A Level Students GCE Notes on s-block Gp 1 Alkali Metals & Gp2 Alkaline Earth Metals

equation keywords: 2Na(s) + 2H2O(l) ==> 2NaOH(aq) + H2(g) 4Na(s) + O2(g) ==> 2Na2O(s) Na2O(s) + H2O(l) ==> 2NaOH(aq) 2Na(s) + Cl2(g) ==> 2NaCl(s) NaOH (aq) + HCl(aq) ==> NaCl(aq) + H2O(l) NaOH(aq) + HNO3(aq) ==> NaNO3(aq) + H2O(l) 2NaOH(aq) + H2SO4(aq) ==> Na2SO4(aq) + 2H2O(l) 2NaOH(aq) + CO2(g) ==> Na2CO3(aq) + H2O(l) Na2CO3 + 2HCl(aq) ==> 2NaCl(aq) + H2O(l) + CO2(g) 2K(s) + 2H2O(l) ==> 2KOH(aq) + H2(g) 2Li(s) + 2H2O(l) ==> 2LiOH(aq) + H2(g) 2NaNO3(s) ==> 2NaNO2(s) + O2(g) 2KNO3(s) ==> 2KNO2(s) + O2(g) ) ==> 2NaCl(aq) + H2O(l) + CO2(g)   2K(s) + 2H2O(l) ==> 2KOH(aq) + H2(g) 2Li(s) + 2H2O(l) ==> 2LiOH(aq) + H2(g)

Revision KS4 Science GCSE/IGCSE/O level Chemistry Information Study Notes for revising for AQA GCSE Science, Edexcel GCSE Science IGCSE Chemistry & OCR 21st Century Science, OCR Gateway Science  WJEC gcse science chemistry CCEA/CEA gcse science chemistry (revise courses equal to US grade 8, grade 9 grade 10) for revising science chemistry courses revision guides

Alphabetical Index for Science Pages Content A B C D E F G H I J K L M N O P Q R S T U V W X Y Z