Composition of Matter All matter is composed of Atoms Protons Found in the nucleus of atom positive...
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Transcript of Composition of Matter All matter is composed of Atoms Protons Found in the nucleus of atom positive...
Composition of MatterAll matter is composed of Atoms
Protons Found in the nucleus
of atom positive (+) charge Mass Value 1
Neutrons found in nucleus of
atom neutral (no) charge Mass value 1
Electrons found in clouds
orbiting around nucleus
negative (-) charge Mass value 0
Periodic Table of ElementsEach element is made up of same atoms
1
H
Hydrogen
1.0079
Atomic Number = Number of Protons (# P = # of electrons)
Symbol – 1st letter always CAPITAL 2nd letter always lower casedName
Atomic Mass = Number of Protons + Number of Neutrons
Number of Neutrons = Atomic Mass - Atomic Number
Number of electrons must equal the number protons
or the atom will be charged (+ or -) = Ion
Atomic Models
Most often represented as series of circles
Center circle represents
the nucleus - containing the
protons (P+)and neutrons (N)
Outer circles represent
the electron clouds where
electrons (e-) orbit
Bohr’s Model
6P
6N
e-
Each valence (orbit) has a specific number of electrons it can hold
1st holds up to 2 e- 2nd holds up to 8 e- 3rd holds up to 8 e- 4th holds up to 18 e-
e-
e- e-
e-
e-
Carbon atom
Must remember that:
Bohr’s Models are simple 2D models Atoms are actually 3D
Electrons actually move around nucleus in an electron cloud not a linear orbit
Atoms are active – drawings are stationary
Lewis Dot Model
Uses dots to show Valance electrons – outermost orbit
Valence Electrons are the ones that make the atom interactive
Arranged in pairs on 4 sides of symbol – Shows “empty seats”
N
Why do Atoms React?
They want to fill their “empty seats” on valence orbit Nitrogen has 3 “empty seats”
Can add or lose electrons IONic bond Can share electrons Covalent
N
X
X
X
Types of Bonds
Ionic BondsAtoms may gain or lose electrons to fill its valence shellThis creates an imbalance of + and – creating a charged atom or IONOpposites attractEx Na+Cl-
Covalent BondsAtoms may share electrons to fill valence shell ex. H2O
Hydrogen BondsOccur between H (only have 1 electron)
weak bondEx surface tension between H2O molecules
Why is Carbon so Important?
• Carbon has 6 protons; therefore has 6 electrons
• This leaves 4 empty seats for Carbon to fill
• Carbon will bond with LOTS of things BUT likes to bind with other C atoms.
• This creates the rings and chains of all the organic compounds
Molecules and CompoundsMOLECULE – 2 definitions
1) 2 or more atoms of the same element
joined together O2; H2; O3
2) Smallest unit of a compound that has the properties of that compound
COMPOUND2 or more different elements chemically
combined
H2O; CO2; C6H12O6
Polarity of Water
Water (H2O) is made up of 2 H and 1 O sharing their electrons (covalent bond)
There is a higher concentration of electrons on the Oxygen end making it slightly negative and the Hydrogen end slightly positive
Lipids are insoluble in water
Because they are•Not polar•Have no ionic bondsTherefore, they are NOT attracted to water
pH The concentration of H+ in a
solution measures the acidity or basicity of the solution H2O will break apart creating hydrogen ions
(H+ ) and hydronium ions (OH-) More H+ = acid (< 7) More OH- = basic (alkaline) (>7) Equal amounts H+ & OH- = Neutral (pH7)
States of Matter:Matter on Earth can be found in three states:
SOLIDS – molecules are barely moving; (ice cube)
Little energy Definite volumeDefinite Shape
States of Matter
LIQUIDS - molecules moving fairly freely (water)
More energy Definite volume No definite shape
States of Matter
GASES – molecules are moving rapidly (steam)
Lots of energyNo definite volumeNo definite shape
Physical Change
How do you know you saw a PHYSICAL CHANGE?
Change in:State, shape or size…
Change in STATE
Solid
Gas
Liquid
Change in SIZE
Change in SHAPE
Chemical Change
How can you tell there was a CHEMICAL REACTION!? Something
NEW is formed…
New solid formed
Precipitate
Unexpected color change
Clear + Clear PURPLE
Temperature change
Increase (endothermic) or
Decrease (exothermic)
New gasformed
Bubbles
Odor/smell
Steam
Quiz – Identify as Chemical or Physical Change
Slicing bread Physical
Rust on nail
Baking bread
Melting Ice cream
Chemical
Chemical
Physical