CHEMISTRY!!!!
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Transcript of CHEMISTRY!!!!
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Subatomic particles
ElectronProton
Neutron
Name
Symbol
Charge
Relative mass
Actual mass (g)
e-
p+n0
-1+10
1/1840
1
1
9.11 x 10-
28
1.67 x 10-
241.67 x 10-
24
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Counting the Pieces Atomic Number = number of
protons in the nucleus # of protons determines kind
of atom The same as the number of
electrons in the neutral atom. Mass Number = the number of
protons + neutrons. These account for most of
mass
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Counting the Pieces
Protons: equal to atomic number
Neutrons: Mass Number – Atomic Number
Electrons: In a neutral atom equal to atomic number
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Symbols
Contain the symbol of the element, the mass number and the atomic number.
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Symbols Contain the symbol of the
element, the mass number and the atomic number.
X Massnumber
Atomicnumber
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Symbols Find the
number of protons
number of neutrons
number of electrons
Atomic number Mass Number
F19 9
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SymbolsSymbols Find the Find the
–number of protonsnumber of protons
–number of neutronsnumber of neutrons
–number of electronsnumber of electrons
–Atomic numberAtomic number
–Mass NumberMass Number
Br80 35
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SymbolsSymbols if an element has an atomic if an element has an atomic
number of 34 and a mass number number of 34 and a mass number of 78 what is the of 78 what is the
–number of protonsnumber of protons
–number of neutronsnumber of neutrons
–number of electronsnumber of electrons
–Complete symbolComplete symbol
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SymbolsSymbols if an element has 91 protons and if an element has 91 protons and
140 neutrons what is the 140 neutrons what is the
–Atomic numberAtomic number
–Mass numberMass number
–number of electronsnumber of electrons
–Complete symbolComplete symbol
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What if Atoms Aren’t Neutral Ions: charged atoms resulting
from the loss or gain of electrons
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What if Atoms Aren’t Neutral Anion: negatively charged ion;
result from gaining electrons Take the number of electrons in a
neutral atom and add the absolute value of the charge
81
35
Br1- Identify:
Number of ProtonsNumber of NeutronsNumber of Electrons
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What if Atoms Aren’t Neutral Cation: positively charged ion;
result from the loss of electrons Take the number of electrons in a
neutral atom and subtract the value of the charge
27
13 Al 3+
Identify:Number of ProtonsNumber of NeutronsNumber of Electrons
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Isotopes
Atoms of the same element can have different numbers of neutrons
Different mass numbers Called isotopes
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Naming Isotopes
We can also put the mass number after the name of the element.
carbon- 12 carbon -14 uranium-235
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Atomic Mass How heavy is an atom of oxygen?
There are different kinds of oxygen atoms
We are more concerned with average atomic mass
Average atomic mass is based on abundance of each element in nature.
We don’t use grams because the numbers would be too small
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Measuring Atomic Mass
Unit is the Atomic Mass Unit (amu)
It is one twelfth the mass of a carbon-12 atom
Each isotope has its own atomic mass, thus we determine the average from percent abundance
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Atomic Mass
Is not a whole number because it is an average.
are the decimal numbers on the periodic table.
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Modern Periodic Table
The modern periodic table consists of Rows and Columns
Rows - Horizontal Also known as Periods Numbered 1-7
Columns - Vertical Also known as Groups and Families Numbered 1-18
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Metals
The most common class of elements is Metals
Metals become cations What is a cation? How are they formed?
Positively charged atom - Lose electrons
Metals are generally solid (except Hg), conductive of heat and electricity, malleable, ductile, and shiny
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Alkali Metals
Group 1 elements are known as Alkali Metals
Alkali metals include Li, Na, K, Rb, Cs, Fr
Alkali metals are generally dull, soft, and reactive – rarely found as free elements
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Alkaline Earth Metals
Group 2 elements are known as Alkaline Earth Metals
Alkaline earth metals include Be, Mg, Ca, Sr, Ba, and Ra
Alkaline earth metals are harder, denser, and stronger than alkali metals
Less reactive than alkali metals, but still rarely found as free elements
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Transition Metals
Elements in groups 3-12 (3B-2B) are known as Transition Metals
Transition metals include Mn, Fe, Ag, Au, Mo, etc.
Lanthanide and Actinide Series elements fill in the f orbitals – known as inner transition elements
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Metalloids
Elements that border the staircase on the periodic table are known as Metalloids
Metalloids include: B, Si, Ge, As, Sb, Te, Po, At
Metalloids have properties of both metals and nonmetals
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Nonmetals
Nonmetals are found to the right of the staircase on the periodic table
Nonmetals generally become anions What is an Anion? How are they formed?
Negatively charged atom - Gain electrons
Nonmetals are often gases or dull, brittle solids
Nonmetals generally show poor conductivity, ductility, and malleability
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Halogens
Group 17 elements are known as Halogens
Halogens include F, Cl, Br, and I
Halogens are the most reactive nonmetals – often found in compounds
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Noble Gases
Elements in group 18 are known as Noble Gases
Noble Gases include He, Ne, Ar, Kr, Xe, Rn
Noble gases are extremely unreactive
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Legend
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C lass ifica tion o f M a tte r
E lem ents C om pounds
Pure Substances
H om ogeneous(SO LU TIO N S)
C o llo ids S uspens ions
H eterogeneous
Mixtures
Matter
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Pure Substances Cannot be physically
separated Every sample has the same
characteristics and they can be used to identify a substance
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Elements Are made up of ONE type of atom
Atoms are the smallest unit of an element that maintains the chemical identity of that element
They can be found on the Periodic Table
Examples: Carbon, Nitrogen, Calcium
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Compounds
Can be broken down into simple stable substances
Are made up of two or more types of atoms that are chemically bonded
Examples: Water (H2O), sugar (C12H22O11)
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Mixtures
A blend of two or more kinds of matter, each which retains its own identity and properties
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Homogeneous Mixtures Have uniform
composition Also known as
SOLUTIONS
Examples: salt water, tea
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Solutions ALLOYS are solid solutions that
contain at least 1 metal They are blended together so that
they have more desirable properties Some alloys you may know are:
Stainless Steel: iron, chromium, and zinc Brass: zinc and copper Bronze: tin and copper Sterling Silver: copper and silver
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Heterogeneous Mixtures
Do not have uniform composition You can see the particles in them
Examples: Sand on the beach (contains sand,
shells, rocks, bugs, etc) Soil (contains dirt, rocks, worms, etc) Chicken Soup (contains water, chicken,
veggies etc)
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Suspensions A heterogeneous mixture where the
solid particles eventually settle out of solution
Examples: Muddy water Mixtures of two solids Paint
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Properties of Matter
All pure substances have characteristic properties
Properties are used to distinguish between substances
Properties are also used to separate substances
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Physical Properties
A Physical Property is a characteristic that can be observed or measured without changing the composition of the substance
Physical properties describe the substance itself
Examples Physical State Color Mass, shape, length Magnetic properties
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Chemical Properties A Chemical Property
indicates how a substance will react with another
Chemical properties cannot be determined without changing the identity of the substance
Examples: Iron Rusting Silver Tarnishing
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Physical Changes
A Physical Change is a change in a substance that does not alter the substance’s identity Examples:
Grinding Cutting Melting Boiling
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Chemical Changes A change in which one or more
substances are converted into different substances is called a Chemical Change
Signs of a Chemical Change: Color Change Gas is Released Temperature Change Precipitate – Solid falls out of solution Substance Disappears
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Electrons
Electrons fill in an atom in energy levels
Electrons occupy the LOWEST available energy level
Energy Levels hold limited amounts of electrons 1st Level – 2 electrons 2nd Level – 8 electrons 3rd Level – 18 electrons 4th Level – 32 electrons
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Chlorine (Cl)
P = 17N = 18E = 17
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Nitrogen (N)
P = 7N = 7E = 7
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Aluminum (Al)
P = 13N = 14E = 13
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Valence Electrons
Electrons in outermost shell that determine chemical behavior
Maximum of 8 valence electrons Atoms with same valence electrons
will act similarly Group 1 elements?
1 valence electron Group 17 elements?
7 valence electrons
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How Atoms Combine
Two or more atoms that are chemically combined make up a compound
The combination results in a chemical bond, a force which holds elements together in a compound
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Covalent Bonds
Covalent Bonds are formed when atoms in a compound share electrons
Molecule – two or more atoms held together by a covalent bond
Usually occurs between nonmetals
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Covalent Bonding in Water
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Ions
An atom that has gained or lost an electron is called an ion.
Multiple atoms can combine to form an ion – called a Polyatomic Ion
Silicate (SiO44-) and Carbonate (CO3
2-) are important in forming materials at Earth’s Surface
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Ionic Bonding
Positive and negative ions attract each other
Ionic Bonds occur when oppositely charged ions form a compound
Usually consist of 1 metal and 1 nonmetal
Positive ion written first in chemical formula (NaCl)
Ionic compounds have a neutral charge
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Ionic Bonding in NaCl
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Metallic Bonds
Metals share valence electrons between all atoms
Like a group of positive ions in a sea of electrons
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Acids and Bases
An Acid is a substance that produces Hydrogen Ions in water (H+)
Acids: Sting to the touch Taste Sour React with metals
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Acids and Bases
A Base is a substance that produces hydroxide ions (OH-) in water
Bases Are slippery to
the touch Taste Bitter Do not react with
metals
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pH Scale
Measures the amount of hydrogen ions in a solution 0 - 6 Acidic 7 = Neutral 8 - 14 Basic
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Indicators• Indicators are substances
that turn colors at different pH levels
• Examples:• Litmus• Phenolphthalein
• Base indicator• Universal Indicator: • ACID NEUTRAL BASE• Cabbage Juice• ACID NEUTRAL BASE