1. DI Biology Jennifer Naples
Chemistry
DI Biology
Jennifer Naples

2. Elements
An element is a substance that can not be broken down into smaller substances
There are 90 naturally occurring elements in nature
All elements are listed in the periodic table

3. Periodic Table of Elements
The periodic table of elements

4. Elements There are 25 elements needed for all living things
96% of the mass of human beings is:
Carbon
Hydrogen
Oxygen
Nitrogen

5. Atoms An atom is the smallest part of an element
There are 4 parts in the arrangement of an atom
Nucleus - the center of an atom
Proton - (+)charged particle found inside of the nucleus
Electron-(-)charged particle found outside the nucleus
Neutron – Particle found inside the nucleus with NO charge

6. Energy Levels Regions where electrons travel around the nucleus
Each energy level can hold a certain number of electrons
1st energy level can hold 2 electrons
2nd level can hold 8 electrons
3rd energy level can hold 18 electrons
All energy levels must be used in order for an element to be stable

7. Example
If an element has 8 total electrons, two will be in the first energy level and the remaining 6 will be in the second level.
Is this element stable?
NO! The second shell is not full
How many electrons would this element need in the second energy level to be stable? 8

8. Electron Configuration
Draw the electron configuration for an atom that has 9 electrons. Is it stable?
Draw the electron configuration for am atom that has 16 electrons. Is it stable?

9. Atomic Number The number found above an element on the periodic table
Is equal to the total protons in the nucleus
Also indicates the number of electrons since protons and electrons always equal one another

10. Determining the Number of p+, n and e-
Protons are always equal to the atomic number
Carbon’s atomic number is 6=6 protons
Electrons are also equal to the atomic number
Unless it is an ion(+ or – charge)
Neutrons=atomic mass - atomic number
Carbon = 12 atomic mass, 6 atomic number =
6 neutrons

11. Practice Problem
Find the number of protons, neutrons and electrons for helium:
2 protons, 2 neutrons, 2 electrons

12. How Elements Combine
Compound – a substance that is made from two or more different elements bound together
Example: Salt(NaCl) or water (H2O)
Molecule – a group of atoms held together by covalent bonds
Example: oxygen (O2)

13. Ions Sometimes atoms have a charge
The charge can be either positive or negative
An ion is created when an atom gains or loses an electron
This charge changes the # of subatomic particles in the element
Example:
Na+2

14. Ions Figuring out the number of P,E and N in an ion:
First figure out the structure for the atom
Change the # of electrons according to the charge listed near the element
K+2
K has 19 electrons
K+2 has a +2 positive charge
Take AWAY 2 electrons
K+2 has 17 electrons

15. Ions Try it yourself: Find the number of electrons for N-1
What is the number of electrons for N? 7
What is the number of electrons for N-1

16. Compounds and Bonding
Compound – a substance composed of elements that are chemically combined
What does it mean to be chemically combined
Chemical vs. Physical change

17. Compounds and Bonding Why do elements combine?
Electrons surround the nucleus in energy levels
In order to be stable the outer valance shell must be filled
The pull on an atom on another electron is known as electronegativity
More electronegativity=more pull on electrons

18. Covalent Bonds When two atoms share electrons Example: water
Strong bonds
Most living things are made
Up of covalent bonds

19. Ionic Bonds When two elements of opposite charge combine.
An ion is an atom that has acquired a positive or negative charge
Example: Na+Cl = NaCl
Weak bonds

20. Chemical Reactions When they occur: Bonds are formed Bonds are broken
Substances are changed or altered into different substances

21. Metaboliosm
Refers to the chemical reactions that take place within an organism

22. Chemical Equations Reactants – substances that undergo the reaction
Products – substances which are formed from a reaction
Subscripts – The number of atoms of each element in a molecule
Coefficient – The number before each chemical formula(number of molecules of that substance)

23. Examples of Chemical Equations
Water

24. pH
pH – refers to the hydrogen ion (H+) versus hydroxide ion (OH-) concentration in a solution
Acid – a substance that has more H+ ions and has a pH BELOW 7
Base – a substance that has more OH- ions and has a pH ABOVE 7

25. pH Scale

26. pH Examples
Pure water has a pH of 7.0 which means it has a equal amount of H+ and OH- ions
Hair remover(Nair) has a pH of 13.0
Soda has a pH of 3.0

27. Ionization When a nonionic compound is converted into ions
Water can go through this process. Water can be converted into H+(Hydronium ions) and OH-(Hydroxide ions)

28. Atomic Mass The number found below an element on the periodic table.
Is equal to the total protons and neutrons in a nucleus