1. CHAPTER 6 – THE CHEMISTRY OF LIFE
SECTION 6.1 – Atoms + their Interactions p

2. Atoms: The Building Blocks of Rocks - and You…
Both living and nonliving things are composed of the basic building blocks called ATOMS

3. Elements
Definition
A substance that can’t be broken down into simpler chemical substances
Examples:
Gold
Tungsten
Helium

4. Elements Only about 25 elements are essential to living things
Four make up 96% of a human body:
Carbon
Hydrogen
Oxygen
Nitrogen

5. Elements Elements are identified by a symbol Trace elements C – Carbon
Ca – Calcium
Trace elements
Elements present in small amounts in living things
Examples:
Iron
Copper
Zinc
Iodine

6. Atoms: The Building Blocks of Elements
Definition
The smallest particle of an element that has the characteristics of that element
Basic building block of all matter

7. Atom - Structure Nucleus Center of the atom Contains:
Protons
Positively charged particles (p+)
Neutrons
Particles with no charge (n0)
Nucleus has a positive charge

8. Atom - Structure Elements differ in the number of protons each has
Example:
Iron vs. Aluminum

9. Atom - Structure Electrons
Small, negatively charged particles that surround the nucleus (e-)
Held in place by its attraction to p+ in nucleus
Found in electron clouds
# electrons is energy levels
1st – 2
2nd – 8
3rd – 18

10. Electron energy levels

11. Isotopes
Definition
Atoms of the same element that have different numbers of neutrons
Examples:
C-12
C-13
C-14

12. Isotopes Uses of isotopes:
Some are radioactive and therefore can be used in radiation treatments
Can be used to estimate age of objects (radioactive dating)

13. Compounds + Bonding Compound
A substance composed of atoms of two or more different elements that is chemically combined
Example:
TABLE SALT - NaCl

14. Compounds + Bonding Most elements in nature are found in compounds
Atoms combine with other atoms to become stable
Outermost energy level is filled
Is this atom stable?

15. Types of Bonds Covalent When two or more atoms share electrons
Example:
Hydrogen, H2
Most compounds in organisms have covalent bonds
Sugars, fats, proteins, + water

16. Types of Bonds Molecule
A group of atoms held together by a covalent bond
Example:
WATER

17. Types of Bonds Ionic bond
The attractive force between two ions of opposite charge
Formed by combining ions – a charged particle made of atoms
Opposites attract – “+” like “-”
Example:
Table Salt

18. How an Ionic bond forms…

19. Chemical Reactions
Occurs when bonds are formed or broken, causing substances to recombine into different substances
Occurs within cells
Metabolism
All the chemical reactions that occur within an organism

21. Chemical Reactions
Chemical reactions are represented by writing CHEMICAL EQUATIONS
Example – the formation of water
2 H2 + 1O2 2 H2O
Reactants
Products
Coefficients
Indicates the # of molecules
Subscripts
Indicates the # of atoms
Equations must be BALANCED!!!

22. Mixtures + Solutions Mixture
A combination of substances in which the individual components retain their own properties
Example:
Sugar + Water
Trail Mix

23. Solutions
Definition
A mixture in which one or more substances are distributed evenly in another
Parts:
Solute
Substance that gets dissolved
Solvent
Substance doing the dissolving

24. Concentration Definition
Amount of solute dissolved in fixed amount of solvent
The more solute dissolved in the solvent, the greater the concentration of the solution

25. Acids + Bases
Chemical reactions can occur only when conditions are right
A reaction may depend upon:
Available energy
Temperature
Concentration of substance pH

26. Acids + Bases pH A measure of how acidic or basic a solution is
Scale ranges from 0 to 14

27. Acids + Bases Acid Substance that forms H+ ions in water
pH range – below 7
Typically sour to taste; can be corrosive
Examples:
Lemon
Tomato
Stomach acid

28. Acids + Bases Neutral Substance that has pH value = 7 Example:
Pure water

29. Acids + Bases Base Substance that forms hydroxide ions (OH-) in water
pH range – above 7
Typically bitter to taste; feels slippery
Examples:
Egg
Drain cleaner
Antacid