chapter 6 state standards: 3.a; 7.b 1contreras. the atom 2contreras
TRANSCRIPT
Chapter 6
State Standards:3.a; 7.b
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The Atom
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There have been many changes that have contributed to what the atomic theory is today
Over centuries many scientist have discovered and clarified information about the atom
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The atom is the smallest particle within an element
An element is made-up of MANY atoms that are exactly the same
Atoms cannot be seen with the naked eye
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It would take 106 million billion Au atoms to cover the surface of a dollar bill70 million He atoms could fit on
your pencil eraser Contreras
Nucleus – small, dense, positively charged center Protons – positively charged particles
in the nucleus Neutrons – particles in the nucleus with
no charge
Electrons – negatively charged particles found in electron clouds outside the nucleus. Determines size of atom.
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Electron Cloud
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Protons 1 amu Positively charged (+)
Neutron 1 amu No charge
The nucleus is the biggest part of the atom
1 amu = 0.0000000000000000000000017 g
Atomic Mass Unit (amu)
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If there was a nucleus the size of a grape, it would have a mass of 9 million metric tons (18 million pounds)!Contreras
Electrons Negatively charged (-) Found only in electron clouds Smallest mass particle of the atom 1/1800 size of proton and neutron
Electron Cloud Region outside the nucleus where
electrons are contained
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Atoms and Elements
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1. Gravitational Force – holds all the parts of the atom together
2. Electromagnetic Force – attracts electrons (-) around nucleus (+)
3. Strong Force – holds protons in nucleus together
4. Weak Force – holds nucleus together in radioactive atoms
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Nucleus has a positive charge (because of protons)
Electrons have negative charge
For an atom to have no charge, positive and negative charges need to be balanced (# of protons and electrons is equal)
An ion is an atom with a charge Positively charged ion = atom has lost 1+
electron(s) Negatively charged ion = atom has gained 1+
electron(s)11Contreras
Atomic number - # of protons in nucleus
Atomic number (# of protons) is the same for all atoms of a certain element
Atomic number tells you what element it is!
Atomic mass (mass number) = protons + neutrons Atomic mass needs to be rounded
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Atomic mass
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Electron Cloud
Maximum # of
Electrons
1 2
2 8
3 18
4 32
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An element’s atomic number tells where it is on the periodic table
Atomic number = # protons (+)
# protons (+) = # electrons (-) As long as the atom is not an ion
Atomic mass = protons + neutrons
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Isotopes
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Atoms of the same element that have different number of neutrons in their nucleus
Isotopes still have same: Atomic number # protons # electrons Different # neutrons
Named according to the mass number hydrogen-1 and hydrogen-2
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Hydrogen has an atomic number of 1
So Hydrogen has 1 proton
Hydrogen has 2 additional isotopes (H with different number of neutrons) Deuterium (1 proton & 1 neutron) Tritium (1 proton & 2 neutrons)
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To find the number of neutrons: Protons + neutrons = mass number Mass number – atomic number (#
proton) = neutrons
Mass numberof Carbon is 12
Mass number: 12Atomic number: - 6# Neutrons: ~6Contreras
An unstable atom where the nucleus will change and eventually fall apart over time
Will give off energy when they fall apart
Ex. Radon; Uranium Found in nature No stable isotope exists
19http://computershopper.com/shoptalk/Radioactive_Man_Number_One_v_1024.jpg
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Ions have a charge Positive charge if lost an electron ▪ K 1+ has lost an electron
Negative charge if gained an electron▪ Cl 2- has gained two electrons
Isotopes Have same number of protons &
electrons, different number of neutrons
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Name Location Charge
Nucleus Center of atom Positive
Proton Nucleus Positive
Neutron Nucleus None
Electron Electron cloud Negative
electron proton/neutron nucleus atom element
smallest mass biggest mass
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