September 18th
Chapter 3: Sections 2, 3, and 4
Chapter 3: Sections 2, 3, and 4
Problem sets?
Rutherford's experiments: nuclear theory of the atom
Atoms made up of three types of particles: protons, neutrons, and electrons.
Protons and neutrons in the nucleus, electrons outside it.
Protons
Protons are packed into the nucleus (along with neutrons)
The mass of one proton is about one amu (atomic mass number)
Number of protons in an atom determines that atom's element.
Number of protons = the atomic number (Z)
Charge on a proton = +1
Number of protons = Total positive charge on an atom
Chemical symbol: shorthand way of designating an element: "H" for
hydrogen, say, or "O" for oxygen.
The Rules: chemical symbols are always:
"Si" is silicon, "SI" is sulfur and iodine.
ALWAYS look at the name of the element before deciding that a symbol is
the correct one for that element. The symbol for sodium is not "S", it is "Na".
Electrons
VERY tiny compared to proton: mass is about 0.00055 amu. Takes about
1800 electrons to equal the mass of one proton.
Zipping through the vast empty space outside the nucleus.
Determines the charge on an atom.
Charge on an electron is -1.
Neutral atom: # protons = # electrons
Positive ion*: # protons > # electrons
Negative ion*: #protons < # electrons
* Ion = atom with a charge
Ions have their charge written as a superscript
following the element symbol: Na+, O2-.
Rutherford's experiments: nuclear theory of the atom
Atoms made up of three types of particles: protons, neutrons, and electrons.
Protons and neutrons in the nucleus, electrons outside it.
Protons
Protons are packed into the nucleus (along with neutrons)
The mass of one proton is about one amu (atomic mass number)
Number of protons in an atom determines that atom's element.
Number of protons = the atomic number (Z)
Charge on a proton = +1
Number of protons = Total positive charge on an atom
Chemical symbol: shorthand way of designating an element: "H" for
hydrogen, say, or "O" for oxygen.
The Rules: chemical symbols are always:
- one uppercase letter OR
- one uppercase letter followed by one lowercase letter
"Si" is silicon, "SI" is sulfur and iodine.
ALWAYS look at the name of the element before deciding that a symbol is
the correct one for that element. The symbol for sodium is not "S", it is "Na".
Electrons
VERY tiny compared to proton: mass is about 0.00055 amu. Takes about
1800 electrons to equal the mass of one proton.
Zipping through the vast empty space outside the nucleus.
Determines the charge on an atom.
Charge on an electron is -1.
Neutral atom: # protons = # electrons
Positive ion*: # protons > # electrons
Negative ion*: #protons < # electrons
* Ion = atom with a charge
Ions have their charge written as a superscript
following the element symbol: Na+, O2-.
Neutrons
Packed into the nucleus along with the protons.
About the same mass as protons.
No charge
The number of neutrons determines the isotope of an element.
Relative mass (amu, approx.) |
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Charge | |||
Location | outside the nucleus |
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Change the number of particles and what else changes? |