2.1 Atoms, Ions, and Molecules KEY CONCEPT All living things are based on atoms and their interactions.

2.1 Atoms, Ions, and Molecules What is biochemistry? Biochemistry is the study of structure, composition (what things are made up of), and chemical reactions that occur in living things. Living things (biotic factors) depend on chemistry for life…so biology and chemistry are closely related!

2.1 Atoms, Ions, and Molecules Living things consist of atoms of different elements. An atom is the smallest basic unit of matter. An element is one type of atom. H O Hydrogen atom (H) Oxygen atom (O)

2.1 Atoms, Ions, and Molecules Elements Pure substances that cannot be broken down chemically into simpler kinds of matter. –Made of only 1 type of atom –A group of atoms of the “same” type. More than 100 elements (91 are naturally occurring)

2.1 Atoms, Ions, and Molecules Important Element Facts There are 25 elements found in living things Trace elements are present in very small amounts, but necessary for survival Four elements make up 96% of living things -COHN

2.1 Atoms, Ions, and Molecules Atomic Model Oxygen atom (O) Nucleus: 8 protons (+) 8 neutrons outermost energy level: 6 electrons (-) inner energy level: 2 electrons (-) An atom has a nucleus and electrons. –The nucleus or central core has protons (+ charge ) and neutrons (NO charge). –Electrons (- charge) are in energy levels outside nucleus.

2.1 Atoms, Ions, and Molecules Periodic Table Atomic Number - # of protons Atomic Symbol – Letters –1 st capital –2 nd lower case Atomic Mass - # of protons and neutrons

2.1 Atoms, Ions, and Molecules To find the number of neutrons, subtract the atomic mass from the atomic number For example : Atomic # = # of protons # of protons = # of electrons Atomic mass = # of protons and neutrons. To find neutrons subtract atomic # and atomic mass

2.1 Atoms, Ions, and Molecules Draw the atomic structure of the following atoms:

2.1 Atoms, Ions, and Molecules A compound is made of atoms of different elements bonded together. Smallest particle of a compound is a molecule Most elements exist as compounds –water (H 2 O) –carbon dioxide (CO 2 ) –many other carbon-based compounds in living things

2.1 Atoms, Ions, and Molecules Molecules Is two or more atoms held together by covalent bonds. 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.

2.1 Atoms, Ions, and Molecules Ions An ion is an atom that has gained or lost one or more electrons. Ionic bonds form because atoms are more stable if the outermost energy level is full –positive ions –negative ions Ionic bonds form between oppositely charged ions Sodium atom (Na)Chlorine atom (CI)Sodium ion (Na + )Chloride ion (CI - ) Na loses an electron to CI ionic bond gained electron

2.1 Atoms, Ions, and Molecules Covalent bonds. A covalent bond forms when atoms share a pair of electrons. Very Strong bond –multiple covalent bonds –diatomic molecules covalent bonds Oxygen atom (O)Carbon atom (C)Oxygen atom (O) Carbon dioxide (CO 2 )