A primary learning objective for Biologists The Chemistry of Life A primary learning objective for Biologists

The Periodic Table of elements

Key Features of Arrangement: Groups - vertical Periods - horizontal Atomic Number – increases from left to right down the periodic table Number of Electrons – increases from left to right down the periodic table Valence Electrons – outer shell

The Nature of Matter Atoms The basic unit of matter Composed of subatomic particles: Protons = positively (+) charged Neutrons = neutral (0) charge Together, Protons and Neutrons make the “NUCLEUS” Electrons = negatively (-) charged In constant motion around the nucleus; attracted to the positively charged nucleus Same number of electrons as protons, so atoms have an overall neutral charge.

The Nature of Matter Elements and Isotopes Element – a pure substance containing one type of atom Each kind of element has the same # of Protons Have a 1 or 2 letter symbol on the Periodic Table Isotopes – atoms of the same element that contain different numbers of neutrons Isotopes of an element have the same number of electrons, so their chemical properties are the same

The Nature of Matter Elements and Isotopes (continued) Radioactive Isotopes – nuclei are unstable and break down over time Uses: Dating Rocks Treat Cancer Kill bacteria “Tracers” of substances in an organism

The Nature of Matter Compounds A substance formed by the chemical combination of two or more elements in definite proportions Written as a chemical formula: examples = H2O (water), NaCl (salt) Properties are very different from the elements that form them

The Nature of Matter Bonds – the transfer or sharing of valence electrons Ionic – bond formed when one or more electrons are transferred from one atom to another Atoms become “ions”  negative charge if an electron is gained (anion), positive charge if an electron is lost (cation) Covalent – bond formed when electrons are shared between atoms Single – 2 electrons, Double – 4 electrons, Triple – 6 electrons Molecule = the smallest unit of most compounds

Bond Jokes:

The Nature of Matter Bonds (continued) Van der Waals = a slight attraction between oppositely charged regions of nearby molecules due to the unequal distribution of electrons in a molecule Hydrogen bonds = attraction between hydrogen and a more electronegative element of a nearby molecule Important in properties of water and DNA