Hydrogen and helium because they only have one electron shell and it only holds up to two electrons in it.
Answer:
Explanation:Elements form compound to form chemical bonds, chemical bonding occurs because atoms of an element become more stable by losing, gaining and sharing elections....
Answer: The black ball will have more mass than the white ball.
Explanation: Density of a substance is defined as the ratio of mass and volume occupied by the substance.
Mathematically,

We are given that the two balls are of same size, which means that the volume of both the balls are same. We are also given that the black ball is more dense than the white ball, which means that the black ball will have more mass.
As, 
Answer:
150 times 1000 is how many meters it is away from earth because kilo means 1000
Explanation:
easy metric conversions