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GCSE Chemical Bonding
You can mix two substances together without either substance changing,
as seen when mixing salt and sand
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In chemical reactions, however, the outcome is very
different as when the atoms of two or more elements react they make a
compound
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When atoms react, they take part in changes which give them a stable
arrangement of electrons
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Ionically bonded atoms lose or gain electrons to form charged particles
called ions
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Sodium (2,8,1) loses an electron if left
with a stable structure like neon (2,8)
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The proton is
positively charged, so the sodium atom has now become a positive ion
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Negative ions are made when non-metals react with metals
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Chlorine has the electronic structure 2,8,7 but by gaining an electron, it
gets the stable structure of argon (2,8,8)
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Therefore, this
chlorine atom becomes a negatively charged ion, otherwise known as
𝐶𝑙 − with an electronic structure of 2,8,8
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They pick a deal which suits them both and both
atoms become stable ions
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This rule applies to the bonding between
Group 1 and Group 7 elements
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This force is called
electrostatic force and it act in all directions
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Sometimes the reacting atoms need to gain or lose two electrons to gain
a noble gas structure
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MgO is made up of
magnesium ions with a double positive charge (𝑀𝑔2+ ) and the oxide
ions with a double negative charge (𝑂2− )
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Another ionic compound is calcium chloride
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Therefore, two chlorine atoms react with every one
calcium atom to form calcium chloride (𝐶𝑎𝐶𝑙2 )
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Charges on the ions in ionic bonds always cancel each other out and the
formula of an ionic compound shows the ratio of ions present in the
compound
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For
example, when non-metals react with non-metals, their atoms share
pairs of electrons to form molecules
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Generally, atoms belonging to non-metals need to gain electrons to
achieve outer energy levels which are stable
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Many covalently bonded substances consist of small molecules like 𝐻2 𝑂
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These are often referred to as macromolecules
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Silicon dioxide is similar in structure
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Often seen as a lattice
of positively charged ions
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Strong electrostatic attraction between the negatively charged
electrons and positively charged ions bond the metal ions to each other
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