The Periodic Table

Select a course.

arrow_back

infoWhy this? The periodic table organises elements so that similarities, differences, and trends in their physical and chemical properties become visible and predictable. Its history also demonstrates how scientific models improve through evidence, while group patterns connect electron structure to reactions and reactivity.

scheduleWhy now? This unit builds on Atomic Structure, where atomic number, electron arrangements, and ions were introduced, and Chemical Changes, where reactivity and displacement were explored. We can now use electron structure to explain the behaviour of Group 1, Group 17, and Group 18 elements and recognise broader periodic patterns.

The periodic table is an arrangement of elements in order of increasing atomic number.
Early attempts to classify elements included Döbereiner's triads and Newlands' Law of Octaves.
Dmitri Mendeleev developed the first widely accepted periodic table in 1869, arranging elements by atomic mass and leaving gaps for undiscovered elements.
Mendeleev left gaps in his table to maintain the correct grouping of elements with similar properties, predicting the existence and properties of elements yet to be discovered.
Henry Moseley's work established atomic number as the correct basis for ordering the periodic table, and the atomic number of an element is the number of protons in the nucleus of each atom.
The noble gases were established as a group through discoveries made after Mendeleev's 1869 table and during his lifetime; they were difficult to identify because they are unreactive, and most are scarce.
Francium was discovered in 1939 and was difficult to discover principally because it is extremely scarce and radioactive.
Groups are vertical columns in the periodic table; periods are horizontal rows.
Group 1 elements are called alkali metals; Group 2 elements are alkaline earth metals; Groups 3–12 are transition metals; Group 17 elements are halogens; and Group 18 elements are noble gases.
Metals are found on the left and centre of the periodic table; non-metals are on the right.
Group 1 elements have one outer-shell electron, Group 2 elements have two, Group 17 elements have seven, and Group 18 elements have a full outer shell of eight, except helium, which has two.
Metals have a small number of electrons in their outer shell and tend to lose electrons; non-metals have more electrons in their outer shell and tend to gain or share electrons.
Group 1 alkali metals are soft, have low melting and boiling points, and are highly reactive, especially with water.
The reactivity of Group 1 metals increases down the group.
Group 1 metals react with water to form a metal hydroxide and hydrogen gas; for example, sodium reacts with water to form sodium hydroxide and hydrogen.
Group 1 metals react with chlorine to form metal chlorides; for example, potassium reacts with chlorine to form potassium chloride.
Group 1 metals react with oxygen to form metal oxides; for example, lithium reacts with oxygen to form lithium oxide.
The boiling points of Group 1 metals decrease as you go down the group.
Halogens in Group 17 are non-metals with coloured vapours; their melting and boiling points increase down the group.
The reactivity of halogens decreases down the group.
Halogens react with metals to form salts; for example, sodium reacts with chlorine to form sodium chloride.
A displacement reaction occurs when a more reactive halogen displaces a less reactive halogen from a compound.
The names of the noble gases are helium, neon, argon, krypton, xenon, and radon.
Noble gases are colourless, odourless, monatomic gases at room temperature, with very low chemical reactivity.
Noble gases are unreactive because they have a full outer shell of electrons.

rocket_launchYou must be able to

Sequence the key historical developments in the creation of the periodic table, including the contributions of Döbereiner, Newlands, Mendeleev, and Moseley.
Use connectives such as 'however', 'whereas', 'in contrast', 'as a result', and 'therefore' to compare different stages in the development of the periodic table.
Label groups, alkali metals, transition metals, noble gases, halogens, metals, and non-metals on a blank periodic table.
Identify and colour-code groups and types of elements, including Group 1, Group 2, transition metals, Group 17 halogens, Group 18 noble gases, metals, and non-metals, on a periodic table.
Deduce the number of outer-shell electrons for elements in Groups 1, 2, 17, and 18, including the exception that helium has two outer-shell electrons.
Explain, using atomic structure, why metals are found on the left and non-metals on the right of the periodic table.
Write word and symbol equations for the reactions of Group 1 metals with water, chlorine, and oxygen.
Describe and explain the trend in reactivity and boiling points of Group 1 metals using data and graphs.
Write word and symbol equations for the reactions of halogens with metals and in displacement reactions.
Describe and explain the trends in physical and chemical properties of halogens down the group.
Explain, with reference to electron structure, why noble gases are unreactive.
Describe the physical and chemical properties of noble gases and relate these to their electron configuration.

Curriculum Portal