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1. a group is a vertical column of elements

2. consists of 18 groups of elements

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1. a period is a horizontal row of elements

2. consists of 7 periods of elements, numbered 1 to 7

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electronic configuration across a period

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electronic configuration across a period

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the number of electron shells an element has is the same as its period number

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elements in the same group have the same number of valence electrons

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decrease in metallic properties and an increase in non-metallic properties across a period

this is because across the period, the atom becomes less likely to lose electrons

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1. soft and can be cut easily

2. low melting and boiling points

3. low densities

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1. alkali metal

2. reactivity increases down the group

3. stored in oil to prevent them from reacting with air and water

order of reactivity:

lithium<sodium<potassium<rubidium<caesium<francium

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Group 1 - The Alkali Metals | The Periodic Table | Properties of Matter | Chemistry | FuseSchool

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High melting and boiling point

Most transition metals (except mercury) have very high melting and boiling points because of strong metallic bonding.

High densities

They are denser than group 1 metals (alkali metals) due to their tightly packed atomic structures.

Form colored compounds

When light passes through a compound, some wavelengths are absorbed as electrons in the d-orbitals get excited from a lower energy level to a higher one.

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Variable oxidation state in their compounds

Act as catalysts in a number of industrial processes

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STEMBridge | O Level & IGCSE Made Simple

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Transition Metals – Class 9th Chemistry | Chapter Explained | STEMBridge

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Halogens have low melting and boiling points.

Halogens are coloured

Diatomic molecules

Colour becomes darker down the group

Size of atom increases down the group

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Reactivity decreases down the group

A more reactive halogen displaces a less reactive halogen from its halide solution

displacement reaction: reaction in which one element takes the place of another element in the compound

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Group 7 - The Halogens | Properties of Matter | Chemistry | FuseSchool

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monoatomic non-metals

colourless gases in room temp

low melting & boiling temp

insoluble in water

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unreactive (have full valence shell)

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Noble Gases - The Gases In Group 18 | Properties of Matter | Chemistry | FuseSchool

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increase in metallic properties and a decrease in non-metallic properties

this is due to the size of the atom increases going down a group, so the outermost electrons of the element will be further away from the attractive force of the nucleus