Atoms, Elements and Compounds

1. Basic Chemistry

2. Why do we study chemistry in biology
class?
Because
everything is
made of
different kinds
of elements

3. 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)

5. Atom

6. Elements
An 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

7. 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.

8. 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

9. The Big 6

11. Bonding forms Compounds
1. 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 bonds
o Covalent bonds
1. All bonds involve the atom’s electrons (particularly
the outermost, valence, electrons)

12. 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 electrons
Ex. 1st level = 2 electrons
2nd level = 8 electrons

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

14. 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.

15. Ionic Bonding
Created 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 positive
The atom that gains the electron(s) becomes negative.
Atoms that have a positive or negative charge are called
Ions

16. Example of an Ionic Bond

17. 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?