Properties of Matter, Elements,

Compounds, and Bonding.

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Chemical Properties.

A chemical change pemanantly changes the conpound into another.

Basic unit of matter is an atom

Subatomic particles- protons (+), neutrons, and electrons (-)

Atoms

Protons neutrons in the nucleus

Electrons travel around the nucleus in orbits or clouds or levels of energy.

Atom is neither positive or negative in charge - it is neutral.

ION- An atom that has lost or gained an electron(s)

Identifying Elements

Atomic number- number of protons

The number of protons (atomic number) determines the identity of an element

An element- only one type of atom

Represented by a chemical symbol such as O for oxygen or Na for sodium

CHNOPS- Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorous, Sodium main elements of human body

Isotopes

Atoms of the same element that have a different number of neutrons

Many (not all) are unstable and break down, emitting energy – radioactive isotopes

Used for determining the age of fossils, treatment of diseases, and even to sterilize food.

Chemical Compounds

Compounds- Chemical combination of

two or more elements

Represented by a chemical formula that

indicated the elements in the compound

and their proportions.

Chemical Bonding

In order to become stable, an atom will either gain, lose, or share electrons. Each level can hold only a certain number of electrons. (2,8,8)

Ionic, covalent, and polar covalent bond

Covalent Bonding

Equal Sharing of electrons

Each atom fills it’s outermost energy level

Smallest particle of a compound is a molecule

Ionic Bonding

An ionic bond forms when one atom gains electrons and the other loses electrons

Ions are held together by their opposite charges

Involves atoms of very different sizes

Chemical reactions

The making or breaking of bonds is called a chemical reaction

Reactants (chemicals that enter a reaction) & products (compounds that are produced)

A chemical reaction is indicated by a chemical equation.

Na (+) + Cl (-) ---> NaCl

O2 + 2H2 2H2O

Polar Covalent

The unequal sharing between two atoms (usually one much larger than the other)

Creates slight charge on either side of the molecule.

Hydrogen bond

Between hydrogen and another atom such as nitrogen or oxygen

Weak attractive force that forms temporary, easily broken bonds

Waterimportance for living things

Water has an unusual chemical structure

We are over 70% water

Properties of water

1. less dense as a solid

Found in all three states (solid, liquid and gass) on the earth

2. Water is a good solvent. Many compounds dissolve in water.

3. Water is slow to heat and slow to cool.

4. water is cohesive – water molecules will attract other molecules

5. water is adhesive- water adheres to other molecules

Why?

The bonds are covalent, but the sharing is unequal

The water molecule carries a slight charge

It is polar

Hydrogen Bonds

The slight charge attracts other water molecules

This forms weak temporary hydrogen bonds

As water changes state it adds or breaks apart hydrogen bonds. This slows changes in temperature

solvent

Some hydogen bonds will pull strongly enough to break off a hydrogen ion

H2O H(+) + OH (-)

This will ionize a small portion of the water creating equal numbers of hydrogen and hydroxide ions

solution (solute and solvent)

NaCl Na+ Cl -

PHIn a liter of water only 0.0000001 m/l of water has ionized. (That’s 1x10 ^-7) (PH=7)

PH stands for the percent of hydrogen ions in solution in relation to hydroxide ions

More hydrogen ions are added the ph will go down (example hcl)

If more hydroxide ions (OH) are added then the PH wil go up (example. NaOH)