Chapter 1: The Chemistry of Life

1.1 Atoms, Molecules, & Compounds Matter Anything that has mass & occupies space (pretty much everything you see & even the stuff you can’t see – air)

1.1 Atoms, Molecules, & Compounds Fundamental Units of Chemistry Molecules: particles of a substance that are made up of more than 1 atom All molecules of a substance have the properties of that substance Ex: Water = made of water molecules (H2O) 2 hydrogens & 1 oxygen

1.1 Atoms, Molecules, & Compounds Fundamental Units of Chemistry 2. Elements – Substances that can’t be broken down into anything simpler Examples: Oxygen, Gold, Helium, etc.

1.1 Atoms, Molecules, & Compounds Fundamental Units of Chemistry 3. Atoms – Smallest individual units of elements that retain the properties of that element; simplest form (building block) of matter

1.1 Atoms, Molecules, & Compounds Fundamental Units of Chemistry 4. Compounds – when two or more different types of atoms make up a molecule Compounds are always made up of molecules but a molecule is NOT always a compound. Example: H2O is a compound; H2 is NOT (both are molecules)

1.1 Atoms, Molecules, & Compounds The Elements of Life 97% of compounds in living things are made of a combination of 6 elements: C, H, O, N, P, S These are essential to all life. There are other essential elements, too, but in smaller amounts.

1.1 Atoms, Molecules, & Compounds Chemical Formulas The number of atoms of each element in a molecule can be expressed in a chemical formula Example: CO2 = Carbon dioxide; It has 1 carbon atom & 2 oxygen atoms

1.2 The Structure of Atoms Atoms have 3 smaller components called subatomic particles: Protons – positive charge Neutrons – neutral charge Electrons – negative charge

1.2 The Structure of Atoms Organization of Atoms & Subatomic Particles - Protons & Neutrons make up the nucleus while the electrons orbit around the nucleus

1.2 The Structure of Atoms Electron Shells “Clouds” where electrons are found orbiting the nucleus The shells are distinguished by the # of electrons they can hold: 1st shell: 2 electrons 2nd shell: 8 electrons 3rd shell: 8 electrons - Any valence shell that’s not filled will cause the atom to be reactive. Filled outer shells mean the atom is stable.

1.2 The Structure of Atoms Particle Number of Elements - All atoms have equal numbers of protons & electrons (overall neutral charge).

1.2 The Structure of Atoms Figuring out particle numbers with the Periodic Table of Elements: - Mass number (rounded to whole #) of element = protons + neutrons - Atomic Number of element = # of protons (which equals # of electrons)

1.2 The Structure of Atoms So, the # of neutrons can be calculated by: Electrons, protons = atomic number Neutrons = atomic mass – atomic number Atomic # = 8 Atomic Mass = 16 How many protons, electrons, & neutrons? Review drawing Bohr diagrams/Lewis dot structures

1.2 The Structure of Atoms Isotopes Atoms of the same elements that have different numbers of neutrons  so they have different atomic masses (ex: carbon-12 & carbon-13) Radioactive isotopes can be useful in biological research because we know how long they take to decay so we can determine the age of objects. (Carbon dating)

1.3 Chemical Reactions Chemical bonds – result from the sharing or transferring of valence electrons between/from one atom to another Chemical reactions – take place when chemical bonds are formed or broken

1.3 Chemical Reactions Chemical reactions & living things: Reactions occur in the cells of all living things; Important for 2 reasons: 1. Reactions are the only way to form new molecules the cell needs 2. Reactions cause changes in energy. This energy can be stored or used to do work.

1.3 Chemical Reactions Chemical equations – A representation of a chemical reaction. Example: Decomposition of water 2 H2O  2 H2 + 1 O2

1.4 Chemical Bonds Ions – particles that have positive or negative charge Formed by gaining or losing electrons What happens for an atom to become positive? negative?

1.4 Chemical Bonds Ionic Bonds - an attraction between two oppositely charged ions; relatively strong

1.4 Chemical Bonds Covalent bonds – Results from the sharing of electrons between atoms. These are relatively weak bonds.

1.4 Chemical Bonds Polar Covalent vs. Non-polar Covalent Bonds - Polar bonds = covalent bonds in which the electrons are NOT shared equally (so there are areas with small charges). Why is polarity important? It gives molecules the ability to dissolve in water. Cells are composed of a lot of water and therefore certain molecules can dissolve and be available for movement or reactions.

1.4 Chemical Bonds Example of a polar covalent compound: Water

1.4 Chemical Bonds Non-polar Covalent Bonds - Occur when electrons are equally shared between the atoms.

1.4 Chemical Bonds Hydrogen bonds - weak attractions between the hydrogen (+) of one polar molecule and an N, O, or F (-) of another molecule