subatomic particles electron proto n neutro n nam e symbolcharge relative mass actual mass (g) e-e-...
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Subatomic particles
ElectronProtonNeutron
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
Counting the Pieces Atomic Number = number of
protons in the nucleus # of protons determines kind of
atom (since all protons are alike!)
the same as the number of electrons in the neutral atom.
Mass Number = the number of protons + neutrons.
These account for most of mass
Counting the Pieces
Protons: equal to atomic number
Neutrons: Mass Number – Atomic Number
Electrons: In a neutral atom equal to atomic number
Symbols
Contain the symbol of the element, the mass number and the atomic number.
Symbols Contain the symbol of the
element, the mass number and the atomic number.
X Massnumber
Atomicnumber
Symbols Find the
number of protons
number of neutrons
number of electrons
Atomic number Mass Number
F19 9
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
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
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
SymbolsSymbols if an element has 78 electrons and if an element has 78 electrons and
117 neutrons what is the 117 neutrons what is the
–Atomic numberAtomic number
–Mass numberMass number
–Number of protonsNumber of protons
–Complete symbolComplete symbol
What if Atoms Aren’t Neutral Ions: charged atoms resulting
from the loss or gain of electrons
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
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
Isotopes
Atoms of the same element can have different numbers of neutrons
Different mass numbers Called isotopes
Naming Isotopes
We can also put the mass number after the name of the element.
carbon- 12 carbon -14 uranium-235
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
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
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
Pure Substances Cannot be physically
separated Every sample has the same
characteristics and they can be used to identify a substance
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
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)
Mixtures
A blend of two or more kinds of matter, each which retains its own identity and properties
Homogeneous Mixtures Have uniform
composition Also known as
SOLUTIONS
Examples: salt water, tea
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
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)
Suspensions A heterogeneous mixture where the
solid particles eventually settle out of solution
Examples: Muddy water Mixtures of two solids Paint
Properties of Matter
All pure substances have characteristic properties
Properties are used to distinguish between substances
Properties are also used to separate substances
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
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
Physical Changes
A Physical Change is a change in a substance that does not alter the substance’s identity Examples:
Grinding Cutting Melting Boiling
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
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
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
Covalent Bonding in Water
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
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
Ionic Bonding in NaCl
Metallic Bonds
Metals share valence electrons between all atoms
Like a group of positive ions in a sea of electrons
Atomic Theory and Structure
Democritus
Democritus added: Matter is composed of atoms
which move through empty space Atoms are solid, homogeneous,
indestructible, and indivisible Different atoms have different
shapes and sizes The size, shape, and movement
of atoms determine their properties
Leading to the modern theory Late 1700’s - John Dalton- England. Teacher- summarized results of his
experiments and those of others. Dalton’s Atomic Theory Combined ideas of elements with
that of atoms. Saw atoms as small solid spheres.
Billiard Ball Model.
Dalton’s Atomic Theory All matter is made of tiny indivisible
particles called atoms. Atoms of the same element are
identical, those of atoms of different elements are different.
Atoms of different elements combine in whole number ratios to form compounds.
Chemical reactions involve the rearrangement of atoms. No new atoms are created or destroyed.
Law of Conservation of Mass The law of conservation of mass
states that matter is neither created nor destroyed in chemical reactions
Discovery of the Electron J. J. Thomson - English
physicist. 1897 Made a piece of equipment
called a cathode ray tube. It is a vacuum tube - all the air
has been pumped out.
Thomson’s Experiment
Voltage source
+-
Vacuum tube
Metal Disks
Thomson’s Experiment
Voltage source
+-
Thomson’s Experiment
Voltage source
+-
Thomson’s ExperimentThomson’s Experiment
Voltage source
+-
Passing an electric current Passing an electric current makes a beam appear to move makes a beam appear to move from the negative to the from the negative to the positive endpositive end
Thomson’s ExperimentThomson’s Experiment
Voltage source
+-
Passing an electric current Passing an electric current makes a beam appear to move makes a beam appear to move from the negative to the from the negative to the positive endpositive end
Thomson’s ExperimentThomson’s Experiment
Voltage source
+-
Passing an electric current Passing an electric current makes a beam appear to move makes a beam appear to move from the negative to the from the negative to the positive endpositive end
Thomson’s ExperimentThomson’s Experiment
Voltage source
+-
Passing an electric current Passing an electric current makes a beam appear to move makes a beam appear to move from the negative to the from the negative to the positive endpositive end
Thomson’s ExperimentThomson’s Experiment
Voltage source
+-
Voltage source
Thomson’s Experiment
By adding an electric field
Voltage source
Thomson’s ExperimentThomson’s Experiment
By adding an electric fieldBy adding an electric field
+
-
Voltage source
Thomson’s ExperimentThomson’s Experiment
By adding an electric fieldBy adding an electric field
+
-
Voltage source
Thomson’s ExperimentThomson’s Experiment
By adding an electric fieldBy adding an electric field
+
-
Voltage source
Thomson’s ExperimentThomson’s Experiment
By adding an electric fieldBy adding an electric field
+
-
Voltage source
Thomson’s ExperimentThomson’s Experiment
By adding an electric fieldBy adding an electric field
+
-
Voltage source
Thomson’s ExperimentThomson’s Experiment
By adding an electric field he By adding an electric field he found that the moving pieces found that the moving pieces were negativewere negative
+
-
Plum Pudding Model
Proposed by JJ Thomson
Said the atom had a uniform positive charge in which the negatively charged electrons resided
Lead block
Uranium
Gold Foil
Fluorescent Screen
He Expected
The alpha particles to pass through without changing direction very much.
Because…? …the positive charges were
thought to be spread out evenly. Alone they were not enough to stop the alpha particles.
What he expected
Because
He thought the mass was evenly distributed in the atom
Since he thought the mass was evenly distributed in the atom
What he got
How he explained it
+
Atom is mostly empty. Small dense,
positive piece at center. Alpha particles
are deflected by it if they get close enough.
+
The Bohr Ring Atom
n = 3n = 4
n = 2n = 1
Electron Cloud Theory
What are acids and bases?
ACIDS BASES
TASTE SOUR BITTER
FEEL STINGS SLIPPERY
REACTIONS YES / METAL NO / METALS
CONDUCTS ELECTROLYTE ELECTROLYTE
RELEASES H+ OH-
HOW DO WE MEASURE ACIDS AND BASES?
INDICATORSA SUBSTANCE THAT TURNS ONE
COLOR IN AN ACIDIC SOLUTION AND ANOTHER COLOR IN A
BASIC SOLUTIONSOME INDICATORS ARE:
LITMUS: DYE THAT COMES FROM A LICHEN
PHENOLPHTHALEIN: INDICATES ONLY BASES
UNIVERSAL INDICATOR: ACID, NEUTRALS, BASES CABBAGE JUICE: ACIDS, NEUTRAL, BASE