Covalent Bonding and Simple Molecular SubstancesAQA GCSE Chemistry: Flashcards

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What is covalent bonding?

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What is covalent bonding?: The sharing of pairs of electrons between atoms.
Name the three types of strong chemical bond.: Ionic, covalent and metallic.
Give three examples of simple molecular substances.: Any three of: hydrogen (H2), chlorine (Cl2), water (H2O), carbon dioxide (CO2), methane (CH4).
Why do simple molecular substances have low melting and boiling points?: Only weak intermolecular forces act between molecules, and these are easily overcome — the strong covalent bonds within molecules stay intact.
What happens to melting and boiling points as molecule size increases?: They increase, because larger molecules have stronger intermolecular forces.
Why don't simple molecular substances conduct electricity?: The molecules have no overall charge, and there are no free ions or electrons to carry a current.
What is an intermolecular force?: A weak force of attraction acting between molecules, not within them.
How can a single covalent bond be represented in a diagram?: As a line joining the two bonded atoms, e.g. H–H.
What does a dot and cross diagram show?: The electrons around bonded atoms, using dots for one atom's electrons and crosses for the other's, to show shared pairs.
How many electrons does each hydrogen atom share in H2?: One electron each, forming a shared pair so both atoms have a full outer shell of two.
Is it the covalent bonds or the intermolecular forces that break when water boils?: The intermolecular forces between water molecules break; the covalent O–H bonds within each molecule stay intact.