An element with a valence of 8 are most likely noble gases (He, Ne, Ar, etc) which means they're already stable so they dont need to undergo chemical bonds with another atom because they already have a full valence shell.
Answer:
Explanation:
Given
Airplane is flying with horizontally with a constant momentum during time interval 
Impulse is given by change in momentum, so there is no net impulse on the Plane because momentum is constant
(b) As there is no change in momentum therefore impulse of thrust and air drag is balanced i.e. both are equal in magnitude but act in opposite direction
Answer:
1. bending of light in gravitational fields.
2. effect of gravitational redshift.
3. perihelion precission of mecury.
Explanation:
1 bending of light in gravitational fields, we can think of it like this:
by noting the change in position s of stars as they pass near the sun on the celetial sphere, so since the sun creates a gravitational field even the star thats not in our line of side(behind the sun) can be seen because its light is bent.
2. effects of gravitational redshift:
this says that if you are in the gravitational field, your clock moves slower when it is seen by a distant observer.
3. perihelion precission of mecury:
according to Newtonian physics a two body system consisting of a lone orbiting the spherical mass would trace out an ellipse with the center of mass of the system as the focus but mercury deviates from that precission. then according to Einstein, the change in orientation of the orbital ellipsewithin its orbital plane is the effect of gravitation being mediated by the curvature of space-time.
The continental crust
Hope it helps!!