properties of matter elements compounds and bonding
TRANSCRIPT
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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 (-)
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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)
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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
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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.
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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.
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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
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Covalent Bonding
Equal Sharing of electrons
Each atom fills it’s outermost energy level
Smallest particle of a compound is a molecule
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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
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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
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Polar Covalent
The unequal sharing between two atoms (usually one much larger than the other)
Creates slight charge on either side of the molecule.
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Hydrogen bond
Between hydrogen and another atom such as nitrogen or oxygen
Weak attractive force that forms temporary, easily broken bonds
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Waterimportance for living things
Water has an unusual chemical structure
We are over 70% water
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Properties of water
1. less dense as a solid
Found in all three states (solid, liquid and gass) on the earth
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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
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Why?
The bonds are covalent, but the sharing is unequal
The water molecule carries a slight charge
It is polar
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Hydrogen Bonds
The slight charge attracts other water molecules
This forms weak temporary hydrogen bonds
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As water changes state it adds or breaks apart hydrogen bonds. This slows changes in temperature
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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 -
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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)
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