1. Chemistry

2. The emergence of biological function starts at the chemical level
ATOMS AND MOLECULES
The emergence of biological function starts at the chemical level
Everything an organism is and does depends on chemistry
Chemistry is in turn dependent on the arrangement of atoms in molecules

3. Biological Hierarchy
Each level in the hierarchy builds on the one below it.
Atoms and ecosystems are at opposite ends of the hierarchy

4. Biological Hierarchy

5. Life requires about 25 chemical elements
A chemical element is a substance that cannot be broken down to other substances by ordinary chemical means
25 chemical elements are essential to life
4 MAIN ELEMENTS:

6. Carbon, hydrogen, oxygen, and nitrogen make up the bulk of living matter, but there are other elements necessary for life

7. Elements can combine to form COMPOUNDS
H2O
NaCl

8. The smallest part of an element is an atom Atoms consist of protons, neutrons and electrons
Protons positively charged 2
Protons
Nucleus
Neutrons electrically neutral 2
Neutrons
Electrons negatively charged 2
Electrons

9. Elements consist of ONE type of atom
Atomic Number = # of Protons AND also # of Electrons
Meet the Elements
8 protons
8 electrons
1 proton
1 electron

10. Isotopes
Nonradioactive carbon-12
Nonradioactive carbon-13
Radioactive carbon-14
6 electrons
6 protons
6 neutrons
6 electrons
6 protons
7 neutrons
6 electrons
6 protons
8 neutrons
Isotopes are atoms of the same element that differ in number of neutrons

11. Electrons arrangement determines the chemical properties of an atom
Electrons are arranged in energy levels
The outermost level determines the chemical properties of an atom

12. Atoms are like onions…

13. Octet Rule Level One: 2 electrons Level Two: 8 Electrons
Level Three: 18 Electrons
HOWEVER
Level 3 can hold a maximum of 18, but needs at least 8 electrons to be STABLE

14. Valence Electrons
Valence electrons are the electrons AVAILABLE for bonding
Valence electrons = electrons on outermost level
Worksheet C 6 H 1 O 8 Ar 18

15. Number of Electrons needed for stability
Element
Symbol
Atomic Number
Mass Number
Number of Protons
Number of Neutrons
Number of Electrons
Valence Electrons
Number of Electrons needed for stability
Hydrogen 1
Oxygen 8
Nitrogen 7
Carbon 12
Phosphorus 31
Chlorine 18

16. Atoms whose outermost energy levels are not full tend to interact with other atoms and gain, lose or share electrons
Outermost energy level (can hold 8 electrons)
Electron
First energy level (can hold 2 electrons)
HYDROGEN (H)
Atomic number = 1
CARBON (C)
Atomic number = 6
NITROGEN (N)
Atomic number = 7
OXYGEN (O)
Atomic number = 8

17. Ionic Bonding Protons +11 Protons +17 Electrons -11 Electrons -17
Charge
Protons +17
Electrons -17
Charge

18. Ionic Bonding = Transfer of Electrons
When atoms gain or lose electrons, charged atoms called ions are created
An electrical attraction between ions with opposite charges results in an ionic bond
Protons +17
Electrons -18
Charge
Protons +11
Electrons -10
Charge
Na+
Sodium ion Na
Sodium atom Cl
Chlorine atom
Cl–
Chloride ion
Sodium chloride (NaCl)

20. Sodium and chloride ions bond to form sodium chloride, table salt
Na+
IONIC BONDING =
IONIC COMPOUNDS
Cl–

21. What about these atoms?!
Covalent Bond

22. Covalent Bonding
Some atoms share outer energy level electrons with other atoms, forming a covalent bond
Atoms joined together by covalent bonds = molecules
Practice NH3, CO2

23. **Lewis Dot Structure: include only valence electrons

24. Covalent vs. Ionic Bonding

25. Molecules can be represented in many different ways
Lewis Dot Structure

26. Let’s Practice
BEST SONG EVER