Chapter 6: Chemistry in Biology

Section 1: Atoms, Elements, and Compounds

Journal: This is Biology class, why are we studying chemistry?!

Atom- the smallest unit of matter that cannot be broken down by chemical means ALL matter consists of atoms What 3 subatomic particles make up atoms? Particle Charge Location Electron __ Electron cloud Proton + Core of nucleus Neutron o

Atom

# Protons = # of Electrons So, atoms are electrically neutral

Element Pure substance that cannot be broken down into other substances by physical or chemical means More than 100 known elements; 92 occur naturally Each element has a unique name and symbol.

Label the groups and periods! Chemistry in Biology The Periodic Table of Elements Horizontal rows are called periods. Vertical columns are called groups.

What are the 6 most common elements of biological organisms?

Hydrogen

Oxygen

Carbon

Nitrogen

Phosphorus

Sulfur

1. What are the symbols for the following elements. Oxygen. Lead 1. What are the symbols for the following elements? Oxygen Lead Calcium 2. How many protons are in the following elements? Hydrogen Neon Sodium 3. How many electrons are in the following elements? Carbon Chlorine Iron

Answers 1. What are the symbols for the following elements? Oxygen Lead Calcium O Pb Ca 2. How many protons are in the following elements? Hydrogen Neon Sodium 1 10 11 3. How many electrons are in the following elements? Carbon Chlorine Iron 6 17 26

Chemistry in Biology Isotopes Atoms of the same element that have the same number of protons and electrons but have a different number of neutrons

Chemistry in Biology Radioactive Isotopes When a nucleus breaks apart, it gives off radiation that can be detected and used for many applications.

Chemistry in Biology Compounds A pure substance formed when two or more different elements combine Compounds are always formed from a specific combination of elements in a fixed ratio. Compounds cannot be broken down into simpler compounds or elements by physical means.

Valence Electron Type of electron available to form chemical bonds

Covalent bonds Chemical bond that forms when electrons are shared Chemistry in Biology Covalent bonds Chemical bond that forms when electrons are shared A molecule is a compound in which the atoms are held together by covalent bonds.

Chemistry in Biology Ionic Bonds Electrical attraction between two oppositely charged atoms or groups of atoms

Chemistry in Biology

The elements identified as metals tend to donate electrons. Chemistry in Biology Some atoms tend to donate or accept electrons more easily than other atoms. The elements identified as metals tend to donate electrons. The elements identified as nonmetals tend to accept electrons.

Bonding Analogies Try to come up with analogies to explain the behavior of electrons in both ionic and covalent bonds.

Chemistry in Biology van der Waals Forces When molecules come close together, the attractive forces between slightly positive and negative regions pull on the molecules and hold them together. The strength of the attraction depends on the size of the molecule, its shape, and its ability to attract electrons.

van der Waals Forces Not as strong as ionic or covalent bonds, but play a key role in biological processes!

Opposites Attract

Demo Element or Compound?

Let’s look at an example Let’s look at an example. The element sodium is a silver-colored metal that reacts so violently with water that flames are produced when sodium gets wet. The element chlorine is a greenish-colored gas that is so poisonous that it was used as a weapon in World War I. When chemically bonded together, these two dangerous substances form the compound sodium chloride, a compound so safe that we eat it every day. What is the compound? Common Table Salt!! Sodium metal, Na + Chlorine gas, Cl = Table Salt, NaCl

A Real Bonding Experience… As a group, you will be assigned various elements. Determine the atomic number, atomic mass, protons, neutrons, electrons for each element. Construct Bohr Diagrams and Lewis Structures for your element. Form the Lewis structure, using your group members as electrons. Determine which other elements in the class you are likely to bond with, and decide whether it will be an ionic or covalent bond. Act out the formation of the bond.