Answer:
Elements that are made from only one type of atom
Explanation:
When is at the end of the runway the velocity of the plane is given by the equation

where s=1800 m is the runway length. Thus
At half runway the velocity of the plane is

Therefore at midpoint of runway the percentage of takeoff velocity is
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The molecular geometry of both F2 and HF is linear.There are only two atoms which are covalently bonded and thus, the bonding scheme with the atoms looks like this;
F --- F
H---F
So, both are linear.