Tutor profile: Sara M.

Why doesn't water have a linear shape? If there are two hydrogen and one oxygen, should the shape be a straight line?

You are correct that there are two hydrogen and one oxygen and intuitively, it would make sense for it to make a linear shape, H-O-H. However, we do not see this in nature because of the electron properties in this molecule. Hydrogen has one valence electron so each of these hydrogen can pair up with one of the electrons on the Oxygen. However, Oxygen has 4 valence electrons, which means that even though it is not visible when written out, there is a lone pair of electrons on the oxygen, these electrons repel the positive charge on the hydrogens, giving a bent shape. O / \ H H

What is meant by ionization energy and why does it decrease as you move down the periodic table?

You can think of ionization energy as the energy it takes to pull an electron away from an atom. The energy needed to pull an electron away decreases at the atomic radii increases.

Why is it necessary to multiply all the numbers in parenthesis by the leading number outside the parenthesis? For example 5(6x+5) = 30x +25.

The reason it is important to multiply all number in parenthesis by the leading number in front of the parenthesis is because the numbers in parenthesis act as one unit, so if you want to multiply the 5 times the 6x, you also need to multiply the 5 times the 5.