Structure of Matter
Chemistry deals with the composition of substances and how they change. A knowledge of chemistry is necessary for the understanding of physiology because of the importance of chemical processes in the body.
Elements and Atoms
- Matter is anything that takes up space.
- All matter is composed of elements, 92 of which occur naturally.
- Living organisms require about 20 elements, of which oxygen, carbon, hydrogen, and nitrogen are most abundant.
- Elements are composed of atoms; atoms of different elements vary in size and in how they interact.
Atomic Structure
1. An atom consists of a nucleus containing protons and neutrons, with electrons in orbit around the nucleus.
2. Protons, with a positive charge, are about equal in size to neutrons, which have no charge.
3. Electrons are much smaller and bear a negative charge. (Travel in Cloud).
4. An electrically neutral atom has equal numbers of protons and electrons. 5. The number of protons denotes the atomic number of an element; the number of protons plus the number of neutrons equals the atomic weight.
Bonding of Atoms
1. Atoms form bonds by gaining, losing, or sharing electrons.
2. Electrons are found in shells around the nucleus.
The first energy shell holds two electrons; the other energy shells each hold eight electrons when on the outside.
Draw an atom with 4 protons, 4 neutrons, and 4 electrons.
3. Atoms with incompletely filled outer shells tend to be reactive to form stable outer shells of 8. – (Atoms want 8 or 0.)
4. When atoms gain or lose electrons, they become ions with a charge. Whether they gain or lose will depend on how many they have in the outer shell to start with.
What does your atom above want to do with its electrons?____________________________________
5. Oppositely-charged ions attract each other and form an ionic bond.
6. Covalent bonds are formed when atoms share electrons to become stable with filled outer shells.
a. Two pairs of electrons shared between atoms form a double covalent bond.
Which bond is stronger? _______________________________
Which bond easily dissociates in water NA-CL? __________________
Why are covalent bonds stronger than ionic? ____________________
Molecules and Compounds
1. A molecule is formed when two or more atoms combine.
If atoms of different elements combine, the molecule can also be called a compound.
Compounds always have a definite kind and number of atoms.
Formulas
- A molecular formula represents the numbers and types of atoms in a molecule.
- Various representations, called structural formulas, can be used to illustrate molecules. (Stick Figure Drawings)
Please write the molecular formula for carbon dioxide?_______________
Please draw the structural formula:
Chemical Reactions
1. A chemical reaction occurs as bonds are formed or broken between atoms, ions, or molecules.
2. Those changed by the reaction are the reactants; those formed are the products.
3. Two or more atoms or molecules can be joined during synthesis.- Join to create new
4. Larger molecules can be broken into smaller ones in decomposition reactions. – Breakdown
5. Exchange reactions occur as parts of molecules trade places. – Switching dance partners
6. Reversible reactions are symbolized by using two arrows. – Go Backwards or Forward
7. Catalysts influence the rates of chemical reactions.- Make things happen faster and easier
Give your own definitions for
Synthesis:
Decomposition:
Exchange:
Reversible
Catalysts