It’s All Elementary: Chemistry Basics

8/29/2016 A biologist is studying the relationship between dissolved oxygen levels at various depths in a lake and the number and type of fish species found at each depth. To begin her study, the biologist has recorded dissolved oxygen readings for water samples taken from 1, 5, 10, 15, 20, 25, and 30 meters. Because of a mistake, one of the water samples was incorrectly labeled. Which sample in the table is MOST likely to be incorrect or invalid data?

The teeny, tiny stuff: Atom: Smallest particle of an element that retains the characteristics of that element. Element: The pure chemical substance containing only one type of atom Compound: A combination of elements, chemically bonded

Essential Elements An element is a pure substance that contains only one type of atom. Examples: H – hydrogen C – carbon O – oxygen Elements are usually found combined with other elements as compounds. Compound – a substance formed when two or more elements are chemically bonded. Example – C6H12O6

Structure of an atom: The basic unit of matter is the atom. Atoms have three basic parts: Protons (+ charge) Neutrons (no charge) Electrons (- charge) These are the tiniest and weigh practically nothing.

The Bohr Atom Model The Bohr model is used to visually depict the structure of an atom. Protons and neutrons are located in the nucleus. Electrons are in constant motion in the space around the nucleus.

Periodic Table Crash Course A table of elements, arranged by atomic number Metals are left of the zigzag, Nonmetals to the right (except H) Elements are uncharged, which means the number of protons MUST EQUAL the number of electrons Column numbers tell you valence shell electron number and how they might bond Valence shell electrons: The outermost electrons on an atom. Hydrogen: 1 valence e- Oxygen: 6 valence e- Carbon: 4 valence e-

Bonding – it doesn’t always require glue. There are three basic types of chemical bonds: 1) Ionic – formed when electrons are transferred from one atom to another. This type of bond creates ions. http://www.accessexcellence.org/RC/VL/GG/ecb/ecb_images/02_06_stable_arrangement.jpg

Bonding…… 2) Covalent – formed when electrons are shared between atoms. This type of bond creates molecules. 3) Van der Waals Forces – a slight attraction between oppositely charged molecules. http://www.accessexcellence.org/RC/VL/GG/ecb/ecb_images/02_06_stable_arrangement.jpg

Demo of covalent bonding http://www.teachersdomain.org/asset/lsps07_int_covalentbond/ http://openlearn.open.ac.uk/file.php/1605/SK183_1_002i.jpg

Writing chemical bonds: Molecules can be illustrated in 3 different ways: 1) Chemical formulas – subscripts are used to indicate the number of each type of atom H2O, CH4, CO2 2) Structural formulas - lines are drawn between element symbols to indicate bonds

3) Molecular model – 3D model of what the molecule looks like http://openlearn.open.ac.uk/file.php/1605/SK183_1_002i.jpg

Compounds are NOT Mixtures Mixture: A combination of substances where both keep their original properties. Physically mixed, not chemically mixed. Solution: One or more substances (solutes) are distributed evenly in another substance (solvent) The more solute in a solvent, the higher the concentration. Suspensions: Mixtures of water and non dissolved particles Example: Blood