1. The Chemistry of Life
Biology – Unit 3

2. The Complexity of Life
Put the following words in order from smallest to largest:
Cell, atom, organelle, subatomic particle, molecule, tissues, organism, organ, macromolecule, organ system

3. Atoms Basic unit of matter Atoms are EXTREMELY small
If placed side by side, 100 million atoms would make a row only 1 cm long!
scale/
Atoms are made up of…

4. Subatomic particles The three subatomic particles: Protons Neutrons
Electrons

5. Protons and Neutrons Protons and neutrons have about the same mass.
Protons and neutrons are located in the nucleus of an atom
Protons:
Positively charged particles (p+)
Neutrons:
Particles that carry no charge
“neutral” (no)

6. Electrons Negatively charged particles (e-)
Much smaller than the mass of a proton
In constant motion in the space surrounding the nucleus
Atoms have equal numbers of electrons and protons (negative and positive charges balance out) and atoms are neutral

7. Elements
Where have you heard of the term “elements” before in science? Can you think of any examples?
Element: pure substance that consists entirely of one type of atom
Periodic Table of Elements

8. Periodic Table of Elements

9. Practice Problems How many protons does a sodium (Na) atom have?
How many neutrons does a flourine (F) atom have?
What is the atomic mass for oxygen (O)?
What is the atomic number for phosphorus (P)?

10. Representing Atoms

11. Practice Atomic model for Carbon
Record how many protons, electrons and neutrons are present in a carbon atom using periodic table
Draw the atomic model for carbon
Practice with atomic models and beads

12. Modeling Atoms Lab
Using your notes and a periodic table, work with a partner to model then sketch each atom in your lab notebook.
For each atom record:
Name of element AND symbol
# electrons
# protons
# neutrons
Build and draw the following atoms:
C, H, N, P, O, S

13. Questions
Look at the outer orbital of each atom that you made a model of. How do you think the number of electrons on the outer energy level (valence shell) relates to how stable the element is?
Answer:
Elements with full outer orbitals (valence shells) are more stable and less reactive
Elements with partially complete valence shells are more reactive

14. Questions
Based on what you know about certain elements and their Bohr model, find an element that would have a full valence shell (stable)

15. Questions Fill in each statement A change in the number of protons =
A change in the number of neutrons =
New element
A charged ion
An isotope

16. Isotopes Atoms of an element that have different numbers of neutrons.
Total number of protons and neutrons is the mass number (#protons + # neutrons = mass number)
Isotope
# protons
# electrons
# neutrons
Carbon – 12
Nonradioactive 6
Carbon – 13 7
Carbon – 14
Radioactive 8

17. Radioactive Isotopes Radioactive elements have unstable nuclei
When nuclei are unstable they break down at constant rate over time
Used in determining age of rocks and fossils
Used to detect and treat cancer
Used as a “tracer” to follow movement of substances within organisms.

18. Chemical Compounds Chemical compound- Examples:
Substance formed by the chemical combination of two or more elements in definite proportions.
Written in chemical formulas
Examples:
H2O: 2 hydrogens : 1 oxygen
NaCl 1 sodium : 1 chlorine
NaOH 1 sodium : 1 oxygen : 1 hydrogen
CO2 1 carbon : 2 oxygens

19. Chemical Compounds
H20 vs. H2O2 When the ratio of elements in a compound changes, the physical and chemical properties change as well.
What is the ratio between H’s and O’s in each?

20. Chemical Bonding Atoms are held together by chemical bonds
2 main types:
Ionic bonds
Covalent bonds

21. Lab Activity Model and draw a sodium (Na) and a chlorine (Cl) atom
How many valence electrons are in the outer shells of each atom?
Which atom could easily lose an electron? Explain
Which atom could easily gain an electron? Explain

22. Ionic Bonds
Formed when one or more electrons are transferred from one atom to another
Atoms lose or gain electrons
Lose electrons  becomes positively charged
(+)
Gain electrons  becomes negatively charged
(-)
Atoms that have gained or have lost electrons are ions

23. Ionic Bonds

24. Lab Activity Continued
Model and draw the ionic bond between the sodium and chlorine ions, then draw below.

25. Lab Activity Continued
Methane, CH4, is a molecule that is made up of one carbon atom and four hydrogen atoms.
What do you notice about the outer shell (valence shell) of each of these atoms?

26. Covalent Bonds Electrons are shared between atoms
The structure that is formed when two or more atoms are joined by covalent bonds is a molecule

27. Lab Activity Continued
In order to form the CH4 molecule, the atoms covalently bond to each other. Draw the CH4 molecule on your paper.

28. Questions How do the valence electrons influence molecular bonding?
Answer:
Number of open placed on the valence shell determines the number of bonds the atom can make

29. Lab Activity Continued
Carbon dioxide, CO2, is a molecule that is made up of one carbon atom and two oxygen atoms.
What do you notice about the outer shell (valence shell) of each of these atoms?

30. Lab Activity Continued
In order to form the CO2 molecule, the atoms covalently bond to each other. Draw the CO2 molecule on your paper.