CHEMISTRY. Atoms, Elements & the Periodic Table Describe the structure & parts of an atom.Describe...
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Transcript of CHEMISTRY. Atoms, Elements & the Periodic Table Describe the structure & parts of an atom.Describe...
CHEMISTRY
Atoms, Elements & the Periodic
Table
•Describe the structure & parts of an atom.
•Identify the properties of an atom.•Interpret information on a periodic table to understand how elements
are grouped.
What are the elements made
of?Element-the simplest pure substance.
Elements are made of atoms, and each element’s atoms are unique to that element
Atoms-the basic building blocks of all matter. They are the smallest particles into which an element can be divided and still be the same substance.
Atoms are made of 3 types of particles-protons, neutrons and electrons
The History of Atomic Theory
Democritus – 440 BCE
Greek Philosopher 2445 years ago.
Called particles that made up “stuff” ATOMS
Atomos (Greek word) “not able to be divided”(uncuttable)small hard particlesConstantly move
Dalton - 1803Atoms make up all substances (the elements)
Atoms can not be created, divided or destroyed.
Atoms combine to make other substances.
Conducted experiments
Dimitri MendeleevProposed the laws of the periodic table
1869-developed the first periodic table
Table was arranged according to increasing atomic weight
Left spaces for elements yet to be discovered
J.J. Thomson - 1897Discovered negatively charged particles in atoms called Electrons.
Conducted Cathode Ray Tube experimentLed to the Plum Pudding Model
Ernest Rutherford - 1909
Discovered the nucleus
Nucleus Small tiny very dense center of atoms
Where most the atoms mass is located
Atoms are mostly empty space where electrons are found
Conducted the Gold Foil experiment
Niels Bohr - 1913Electrons move around the nucleus of atoms in definite paths.
Electrons jump between levels from path to path.
Bohr’s model
Most Recent Atomic Theory
Schrodinger and Heisenberg
Electron paths cannot be predicted.
Electrons are likely to be found in regions around the nucleus called electron clouds.
Called the electron cloud model.
Recent Discoveries
Chadwick • 1932-Discovered that neutrons exist
in the nucleus of atoms• Neutrons have no charge and the
mass equal to protons and help to stabilize the atom
Gell-Mann • 1969-Subatomic particles are made of
smaller particles called quarks
PERIODIC TABLE =ORGANIZED ELEMENTS
Elements are:• PURE-Made of like atoms of that
element• Identified by it’s atomic number (#
of protons)• Arrangement of electrons
determines the elements properties (such as conductivity and reactivity).
Link to videohttp://www.privatehand.com/flash/elements7.swfSelect broadband player.
The Element Song
The Structure of an Atom
Protons – POSITIVE charged particles inside the nucleus (center).
Neutrons – neutral particles inside the nucleus that have NO CHARGE!
Electrons – NEGATIVE CHARGED particles in atoms found around the nucleus.
Atomic ParticlesLocation Charge Mass
Protons Nucleus + positive Heaviest particle
Neutrons Nucleus O Neutral -Similar to a proton but carry no charge
Electrons Orbiting outside the nucleus in electron clouds
- Negative •Lightest particle•Smallest part of an atom
Outside the nucleus
• Can be called a electron cloud, shell, energy level, orbit or ring
• Area outside the nucleus where electrons are found
• 1st cloud=2 electrons• 2nd cloud=8 electrons• 3rd cloud=18 electrons
Boron (B)Atomic #=5Atomic Mass=11
Protons=5Neutrons=6Electrons=5
Sodium-(Na)Atomic #=11Atomic Mass=23
Protons=11Neutrons=12Electrons=11
Energy Levels - Electron Clouds
Regions around the nucleus where electrons are arranged.
Electrons further away from the nucleus have more and more energy.
Each level or cloud can hold a specific # of electrons.
1st level - 2 electrons2nd level - up to 8 electrons3rd level-up to 18 electrons
Valence ElectronsThe electrons in the outermost energy level (electron cloud).
Very important because they determine how an element will react with other substances
What’s in the Box?
Atomic Number
Equals the number of protons inside the nucleus of the atom.
Atomic Number=Number of Protons=the number of electrons
Determines the element.
All atoms of an element have the same atomic number.
No two elements have the same atomic number.
5
B10.81Boron
SymbolAll elements have their own unique symbol
Symbols can be one or two letters
The first letter is always a capital letter
The second is always a lower case letter
Symbols don’t always match their English word bc most are from Latin or Greek roots.
Example: Fe=Iron (English) Ferrum (Latin)
5
B10.81Boron
Mass Number
The total number of protons and neutrons in an atoms nucleus.
Number under the element symbol
Protons + Neutrons = Mass Number
Practice: If an atom has 12 protons, 14 neutrons and 12 electrons, what is its mass number?
Practice online
5
B10.81Boron
Atomic Mass Unit - amu
Unit of measurement for the mass of subatomic particles.
1 amu = 1.7 X 10 -24 They are TEENY TINY!!!
.000000000000000000000017 grams
Proton = 1 amuNeutrons = 1 amuElectrons = almost zero (TINIEST particle with the least mass)Most of the mass is in the nucleus with protons and neutronsOtherwise atoms are mostly EMPTY SPACE
Atomic MassRefers to the weight of the atom.
Atomic Mass= Protons + Neutrons
Never negative
Mass
The Charge of an atom
To find the charge of an atom-
1. Find the number of protons (+)
2. Find the number of electrons (-)• Represent the electrons as a negative
number
3. Add the protons and electrons to find the charge
Ex: Calcium atom has 12 protons and 10 electrons. What is the charge of this atom?
Answer 12 proton + 10 electrons 12 + (-10)= +2This atom would be positive (+)
More practice with charge
What is the charge of a copper atom with 26
electrons?
29 protons (+) + 26 electrons (-)
29-26=+3
positive
What is the charge of a Sulfur atom with 18
electrons?
16 protons (+) + 18 electrons (-)
16-18=-2
negative
ReviewAtoms, which contain
Protons (+), neutrons (o)and electrons (-)
#protons
# neutrons
Mass #
Nucleus-contains protons and neutrons
Electron Cloud-electrons orbit the nucleus
Periodic Table Overview
How the Elements are Arranged
Groups/Families:
Similar properties
Periods/Rows:
Increasing atomic number/mass
Groups/FamiliesColumns of the periodic table that consist of elements that have the same number of valence electrons.
Groups 1 and 2 - same # as groupGroups 13-18 - 10 - the group #Groups 3-12 - no general rule.
PeriodsRows of the periodic table that consist of elements with the same number of electron clouds or energy levels.
Alkali MetalsGroup #1
All metals
1 Valence Electron
Very reactive
Alkaline-Earth Metals
Group #2
All Metals
2 Valence Electrons
Very reactive but less than group #1.
Transition MetalsGroups # 3-12
All metals
1-2 valence electrons
Less reactive than group #2
Also contain lanthanide and actinide series (radioactive/unstable).
Groups # 13-16Elements change from metals to nonmetals and include the metalloids.
Atoms have 10 fewer valence electrons than the group #.• Boron Group #13 - 3 valence
electrons• Carbon Group #14 - 4 valence
electrons• Nitrogen Group #15 - 5 valence
electrons• Oxygen Group #16 - 6 valence
electrons
HalogensGroup 17
All nonmetals
7 valence electrons
Very reactiveOnly need to gain 1 more electron.
Noble GasesGroup # 18
All nonmetals
8 valence electrons - except helium only has 2.
UnreactiveHave a full outer electron cloud (energy level).
Hydrogen stands alone
1 valence electron
Very reactive
Reacts violently with Oxygen under the right conditions.
Everyday Uses
IsotopesAtoms of elements that have the same number of protons (atomic number) but a different number of neutrons inside the nucleus.
IonsCharged particles that form during chemical changes.
Form when one or more valence electrons are transferred from one atom to another.
Ions are Charged! + or -
Atoms that lose electrons become positive ions.
Atoms that gain electrons become negative ions.
Cl gains an electron from Na to form NaCl -
Cl ion is negative - more electrons (-)
Na ion is positive - more protons (+).