1. Chapter 1: The Chemistry of Life

2. 1.1 Atoms, Molecules, & Compounds
Chemistry= study of the composition, structure, properties, and reactions of a substance.
Matter= Anything that has mass & occupies space
(pretty much everything you see & even the stuff you can’t see – air)
Mass= The quantity of matter an object has

3. Atoms Basic unit of matter
Smallest individual units of elements that retain the properties of that element
Composed of
protons (+)- positive charge
neutrons (0)- neutral charge
electrons (-)- negative charge

4. Atoms
Protons and neutrons are located in a central area called the nucleus.
Electrons move about the nucleus.
All atoms have an equal # of electrons and protons. (They are neutral)

5. Structure of Atoms: Bohr Model
Electron Shells- “Clouds” where electrons are found orbiting the nucleus
Each shell (other than first) holds 8 electrons
1st shell: 2 electrons
2nd shell: 8 electrons
3rd shell: 8 electrons
ex: Hydrogen (1), Carbon (6), Oxygen (8), Chlorine (17)
Any unfilled outer shell will cause the atom to be reactive. Filled outer shells means the atom is stable.

6. Elements CARBON-C OXYGEN-O HYDROGEN-H NITROGEN-N
A pure substance that contains only one type of atom
About 96% of the mass of all kinds of living things is composed of a combination of just 4 elements…
CARBON-C
OXYGEN-O
HYDROGEN-H
NITROGEN-N

8. Isotopes
Atoms of the same element that have different number of neutrons
Mass number (Atomic mass) = number of protons plus neutrons in nucleus of atom
NOT the same as Atomic Weight (on Periodic Table)
Useful in biological research: we know how long they take to decay, so can be used to determine the age of objects.

9. Isotopes Examples: carbon-12, carbon-13, carbon-14 Carbon – 12
# protons
# neutrons

10. Periodic Table Developed as a way to organize elements
Elements are found in order of atomic number (# of protons)
Atomic weight (# of protons + # of neutrons) get bigger as you go across and down
Periods of elements = rows
As you go across a row, elements get smaller in size BUT greater in mass
Groups of elements = columns
Elements in the same group have similar properties and will bond in similar ways

12. Information on the Periodic Table2 He
Helium 4
Atomic Number
Chemical Symbol
Element Name
Atomic Mass
***Element Song***

13. Compounds
A substance formed by the bonding of two or more elements in definite proportions
Fundamental Units of Chemistry
Physical & Chemical properties of compound are DIFFERENT from each element alone

14. Compounds Chemical formula = composition of the compound
Shows the number of atoms of each element in a molecule
Examples: H2O, NaCl, CO2

15. Chemical Bonds
The forces that hold together the atoms that make up compounds
Result from the attraction, sharing, or transfer of valence shell electrons from one atom to another
Two types of chemical bonds:
Ionic Bonds
Covalent bonds

16. Ionic Bonds A TRANSFER of electrons takes place
ALWAYS between a metal and a nonmetal
Results in ions, or a charged “atom” (+ or -)
Ions of opposite charge attract strongly form an ionic bond

17. **Atoms want their outermost shell to be full**
Ionic Bonds
Example: NaCl
Remember
Rule=
2-8-8!
The number of electrons in outer energy shell determines the chemical properties of an atom.
**Atoms want their outermost shell to be full**

18. Ionic Bonds
When sodium chloride (NaCl) is formed, one electron from sodium is transferred to chlorine.

20. Ionic Bonding Examples: Calcium Fluoride Lithium Nitride
Magnesium Oxide

21. Covalent bonds involves SHARING of electrons
single covalent bond = share one electron
double covalent bond = share two electrons…etc.
result of covalent bond- a molecule, the smallest unit of a compound
Example: Methane (CH4)

23. Covalent bonds
In a double bond, 2 atoms share 2 pairs of electrons (4 electrons)

24. Covalent bonds
In a triple bond, 2 atoms share 3 pairs of electrons (6 e-)

25. Structure of the 4 elements that make up most of the mass of living things: