Atoms and Their Interactions 6.1

Elements Elements A substance that can not be broken down into simpler chemical substances The Periodic Table lists all known elements

Atoms: The Building Blocks of Elements Smallest particle of an element that has the characteristics of that element Structure of an Atom Nucleus Protons (Positive) Neutrons (Neutral) Energy levels (outside of the nucleus) Electrons (Negative)

How come atoms do NOT have a charge? In an atom, the number of electrons equals the number of protons. So the number of positive and negative charges balance out, giving the atom a charge of 0.

Fill in the following chart: Particle Location Charge Symbol Electron outside of nucleus In energy levels negative e- Proton Inside the nucleus positive p+ Neutron neutral n0

Energy Levels First energy level Second energy level 2 electrons Second energy level 8 electrons Third energy level 18 electrons Rules for filling in energy levels! The first energy level has to be FULL before electrons can go into the 2nd energy level The 1st and the 2nd energy level has to be FULL before electrons can go into the 3rd energy level

Compounds Compounds are substances made of 2 or more elements that form a molecule (2 or more atoms together). Examples of common compounds: Table Salt - NaCl Oxygen gas – O2 Water – H2O

Properties of Compounds Compounds have BONDS between the atoms It is difficult to separate the parts of a compound Compounds have chemical formulas to tell you what elements are found in the compound and how many atoms of each element are present. The chemical formula for water is H2O. There are two atoms of hydrogen and one of oxygen.

Ionic Vs. Covalent Bonds Ionic Bonds Form when electrons are exchanged between atoms. Covalent Bonds Form when electrons are shared between atoms. Both types of bonds result in all atoms having a full outer energy level.

Chemical Reactions Chemical reactions happen when bonds are formed or broken and recombine to form new compounds All chemical reactions that occur within an organism are referred to as that organism’s metabolism.

Mixtures Mixtures are combinations of 2 or more pure substances or compounds Some common mixtures: Iced Tea Dirt Paint

Properties of Mixtures There are NO BONDS holding mixtures together Mixtures can often be separated Mixtures can occur in any proportions and DO NOT HAVE A SET FORMULA and can use different components

Solutions Solution – mixture of one or more substances uniformly distributed in another substance. Can be solid, liquid, gas ex. Plasma (liquid) brass (solid) copper and zinc soda (liquid/gas) water and CO2

Acids & Bases The Homeostasis of living things depends on the degree of acidity (acid) and alkalinity (base) in certain areas

Acids & Bases Acids= any substance that forms hydrogen (H+) in water. Alkalinity (a/k/a basic solution)= any substance that forms hydroxide ions (OH-) in water

Acids - pH < 7 Sour taste Corrosive on metals Burns skin Ex. Orange juice, vinegar, sulfuric acid *Homeostasis relevance - your stomach must have a certain acidity to function properly

Bases Tastes bitter Slippery Irritate the skin Ex. NaOH -pH > 7 Tastes bitter Slippery Irritate the skin Ex. NaOH Homeostasis relevance- your small intestine needs a certain alkalinity (basic) to function properly

pH Scale Tells you how acidic or basic something is Ranges 0-14 7 = neutral above 7 = base below 7 = acid Ten fold system Measure pH with litmus paper