Answer is:
4-ethyl-1-heptene.Structure of this alkene is in Word document attached.
<span>First find main chain with longest number of carbon atoms, that is chain with seven carbon atoms and it start on the right and going up the three-carbon attachment.
Main chain has double bond between first and second carbon (</span><span>the lowest number)</span><span>, so it is 1-heptene (alkene).
</span>Substituent is on fourth carbon atom, it is alkyl group with two carbon atoms (ethyl).
12gHe/1 × 1molHe/4.0026g × 6.02x10^23atomHe/1mol = 1.8 atoms
To work this out you do 400÷20=20
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