Basic Chemistry

Why do we study chemistry in biology class?

Because everything is made of different kinds of elements

What is Matter Made of?Answer; Atoms

Atoms are composed of;a. Nucleus• Center of the atom• Contains protons (positive) &

neutrons (neutral)b. Electron cloud • Surrounding the nucleus• Contains electrons (negative)

Atom

ElementsAn element is a pure substance that cannot be

broken down into other substances by physical or chemical means.

Made of only one type of atom

F.Y.I. 92 naturally occurring elements 26 found in living things Only 6 elements make up nearly the entire weight

of an organism! 20 trace elements occur in your bodies.

Big “6” (Actually Big “4”)What happens when you mess up driving?

People “HONC” at you!

- Hydrogen (H) 10% of an animal’s weight- Oxygen (O) 63% of an animal’s weight- Nitrogen (N) 4% of an animal’s weight

(Makes up genes and proteins)- Carbon (C ) 19% of an animal’s weight

The Big 6

Bonding forms Compounds1. Elements can combine to form more complex

substances. 2. Compounds are formed when two or more

substances combine in a chemical bond.3. There are two main types of bonds:

o Ionic bondso Covalent bonds

4. All bonds involve the atom’s electrons (particularly the outermost, valence, electrons)

5. Why do elements want to bond together?

Atoms want to have full energy levels, this makes them stable.

Energy Levels are where the electrons are found- each level can hold a specific number of electronsEx. 1st level = 2 electrons

2nd level = 8 electrons

Atoms become more stable by losing electrons or attracting electrons from other atoms - this results in a chemical bond.

Covalent Bonding Chemical bond formed when electrons are

shared. Hint: Covalent = Cooperate Example: The oxygen atoms below are

sharing their valence electrons in order to have a complete outer shell of electrons.

Ionic BondingCreated when atoms give up (donate) or

obtain (accept) electrons to empty or fill the outer energy level.The atom that loses the electron(s) becomes

positiveThe atom that gains the electron(s) becomes

negative. Atoms that have a positive or negative charge

are called Ions

Example of an Ionic Bond

Time for Questions!1. What are the four main elements that

make up living things? 2. When is an atom considered

chemically stable?3. What are the two main types of bonds

that atoms form?4. What is the main difference between

the two types of bonds you listed above?