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

• Atom– 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 nucleusIn energy levels

negative e-

ProtonInside the nucleus positive p+

NeutronInside the nucleus neutral n0

Energy Levels• First energy level

– 2 electrons• Second energy level

– 8 electrons• Third energy level

– 18 electronsRules 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

SolutionsSolution – 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 & BasesThe Homeostasis of living things depends on the

degree of acidity (acid) and alkalinity (base) in certain areas

Acids & BasesAcids= 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-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