Atoms

This link will take you to the Khan academy page that has all of the Chemistry of Life Videos. These are only optional but if you want a more in depth explanation of chemistry you can go through these videos.

All the Videos on The Chemistry of Life

Class discussion: (In Classroom)

Turn to a partner and discuss what the word Atom means to you. What is an atom? Is everything really made up of atoms or are there some things that are not made of atoms?

There are three subatomic particles

     -Neutron

     -Protron

     -Electron

-Protons have a positive (+) charge

-Neutrons have no charge

-Electrons have a negative (-) charge

The number of protons is what makes an element

     -Atomic Number - how many protons the element has

     -Atomic Mass - how many protons + neutrons the element has

     -If you subtract the atomic number from the atomic mass you will know how many neutrons the element has

The periodic table is organized by atomic number

You can change an element's number of electrons and number of neutrons but you cant change its number of protons. If you change the number of protons you change the element.

-Isotope - different number of neutrons than protons

-Ion - different number of electrons than protons

-Ions have a charge. If they have more electrons than protons then they are negatively (-) charged. If they have less electrons than protons then they are positively (+) charged.

Electron Shell

-The first shell holds 2 electrons

-The second shell holds 8 electrons

-All atoms want to have a full outer electron shell. The last shell of an atom is called the valence electron shell and all electrons in that shell are called valence electrons

-The amount of valence electrons an atom has determines its properties and how it reacts

-The noble gases all have full valence electron shells so they do not react with anything

-Some elements will try to take electrons or get rid of electrons to fill its shell

-If an atom has less than 4 valence electrons it is easier to just get rid of them and drop down to its other shell making it a positive (+) ion

-If an atom has more than 4 valence electrons it will try to take electrons to get to 8 to become a negative (-) ion

Molecules and Bonding

The valence electrons of atoms interact to form bonds.

Molecule - two or more atoms bonded together

-There are multiple types of bonds

Ionic bond - The electrical attraction between positively and negatively charged ions

-When ions are formed they either give up an electron becoming positive or they take an electron becoming negative. This charge causes them to be attracted to oppositely charged ions. If an ion is negatively charged by one it will be attracted to an ion that is positively charged by one.

-Ionic bonds are not very strong. The atoms are not sharing electrons, they are only attracted to each other and stick in a crystal like pattern.

Covalent Bond - When two or more atoms share valence electrons.

     -Sometimes atoms will share their outermost electrons in order to complete their last shell. When they do this they are forming a covalent bond. This type of bond is very strong because the electrons are orbiting both atoms.

Water has many amazing properties that allow life on this earth possible. If water did not have the structure it does we would not exist!

Polar molecule- A molecule having a positive end and a negative end

     -When water molecules stick to other water molecules it is called a hydrogen bond.

Hydrogen Bond - When the positive ends of hydrogen stick to the negative end of oxygen. Hydrogen bonds are very weak.

Cohesion - Water sticking to water because of the hydrogen bonds

     -Cohesion causes surface tension which is the waters surface resisting being broken

Adhesion - water sticking to other molecules other than water