1. CHEMISTRY for BIOLOGY

2. Atoms
The simplest particle of an element that retains all the properties of that element
Consist of:
protons (+) and neutrons (o) inside the nucleus
Electrons (-) orbiting outside the nucleus

3. Periodic Table
Elements are arranged by their atomic number on the Periodic Table
The horizontal rows are called Periods & tell the number of energy levels
Vertical groups are called Families & tell the outermost number of electrons

5. Elements
Pure substances that cannot be broken down chemically into simpler kinds of matter
More than 100 elements (92 naturally occurring) 5

6. Elements Quiz: Know the element name & symbol for…
Hydrogen (H)
Carbon (C)
Nitrogen (N)
Oxygen (O)
Phosphorus (P)
Sulfur (S)
Potassium (K)
Sodium (Na)
Calcium (Ca)
Chlorine (Cl)
Magnesium (Mg)
Iron (Fe)
Most Common Elements in the Human Body: C H N O P S

7. Compounds Most elements do not exist by themselves
A compound is a pure substance made up of atoms of two or more elements
The proportion of atoms are always fixed
Chemical formula shows the kind and proportion of atoms of each element that occurs in a particular compound

8. Molecules are the simplest part of a substance that retains all of the properties of the substance and exists in a free state
Some molecules are large and complex

9. Chemical Formulas
Subscript after a symbol tell the number of atoms of each element
H20 has 2 atoms of hydrogen & 1 atom of oxygen
Coefficients before a formula tell the number of molecules
3O2 represents 3 molecules of oxygen or (3x2) or 6 atoms of oxygen

10. Most atoms are not stable in their natural state
Tend to react (combine) with other atoms in order to become more stable (undergo chemical reactions)
In chemical reactions bonds are broken; atoms rearranged and new chemical bonds are formed that store energy

12. Chemical Reactions Arrow means “yields” or “produces” Reactants
What goes in
What comes out
Reactants
Products
Bonds in the reactants are broken in order to get the products!
-Exothermic reaction: A reaction in which energy or heat is released
-Endothermic reaction: A reaction in which energy or heat is absorbed

13. Covalent Bonds
Formed when two atoms share one or more pairs of electrons

14. Ionic Bonds Some atoms become stable by losing or gaining electrons
Atoms that lose electrons are called positive ions

15. Atoms that gain electrons are called negative ions
Because positive and negative electrical charges attract each other ionic bonds form

16. Atomic Number Number that identifies an element
Determines its place on the periodic table and chemical properties
Atomic # = # of protons
Ex: Carbon has 6 protons
Atomic Number

17. Atomic Mass The mass of an atom
Equal to the number of protons and neutrons in an atom
Why is Atomic Mass shown as a decimal?
Isotopes- same element but atoms with different number of neutrons
Atomic Mass is an average of an element’s isotopes found in nature
Atomic Mass

18. Practice! * protons = electrons in a neutral atom
Element
Atomic #
Atomic mass
Protons
Neutrons
Electrons
Carbon 6
12  6   6 7 3
Phosphorus 31 35 45
Neon 10 30 26