Chemistry, Bonding and Water Notes Elements
is anything that takes up space and has mass.
There are 92 which cannot be broken down into other substances.
Two more elements combine together to make .
What four elements make up 96% of all living matter?
elements occur in very small quantities.
For example, 0.15 milligrams of iodine is required for normal activity of the human thyroid gland.

Atoms
Atomic #: # of in the nucleus.
Atomic mass: # of and in the nucleus.
Elements in the same vertical column on the periodic table have the same # of valence .
The nucleus of an atom contains (+) and neutrons (neutral).
are negatively charged and travel at high speeds around the nucleus.

Electron Shells
The first electron shell can hold only ___ electrons. The two electrons of Helium fill the first shell.
The second shell can hold up to __ electrons. Neon, with 10 electrons, has 2 in the first shell and 8 in the second, filling both shells.
The third shell can hold up to ___ electrons.

Chemical Bonds
Elements always want to be stable so they will often form with other elements.
Chemical bonds are formed when atoms share or transfer .
A covalent bond is formed when atoms their electrons.
If electrons are shared equally and there is no overall charge, it is covalent bond.
If electrons are NOT shared equally and partial charges result then it is considered to be a covalent bond.
The transfer of electrons from one atom to another forms an bond.
In a polar covalent molecule, are not shared equally.
Hydrogen often has charge in a polar covalent molecule (since electrons aren’t shared equally). It will often then be attracted to atoms that are charged.
bonds form between a partially positively charged Hydrogen atom and a partially negatively charged other atom (often O or N).
Hydrogen bonding is especially important between molecules.

5) Properties of Water
Water has very unique chemical and physical properties due to its .
This means the molecule is slightly on each end due to the unequal sharing of electrons between the 2 H’s and the O.
The slightly negative regions of one molecule are attracted to the slightly positive regions of nearby molecules forming bonds.
The ability of water to stick to itself is called (like to like). This is responsible for surface tension.
The ability of water to stick to other polar molecules . This allows water to cling to the cell walls of plants.
Water can move upward when adhesion is greater than cohesion. This is essential for the transport of water in plants.
Water has a high and resists changes in temperature. This stabilizes ocean temperatures, moderates air temperatures and helps keep our internal temperature stable.
When water evaporates it takes a lot of heat with it. This is known as a high heat of . Sweating cools us down by taking heat away from us when water evaporates.
The solid form of water is dense than the liquid form of water; therefore, ice floats on top of water. This allows aquatic animals to survive under ice when it’s cold.
One molecule of water can make __ Hydrogen bonds with its neighbors.
Water is the universal ; it will dissolve other polar molecules like itself (like dissolves like).
Water interacts with ionic compounds. The negatively chargedin water will interact with positive atoms and the positively charged in water will interact with negative atoms.