Download Protons neutrons electrons Charge Positive neutral negative Mass

Protons neutrons electrons
Charge Positive
neutral
negative
Mass 1amu
1amu
0 amu
Volume
0
0
all
Location Nucleus
Nucleus
Cloud
Symbol
p+
n0
e-
Democritus
• Atomos = uncuttable/indivisible
• Smallest part of matter
• No real evidence
Dalton
• Gathered evidence supporting Democritus' hypothesis
• Small tiny sphere = atom
• Atoms of the same element are all alike
• Atoms of different elements are different from each other
• Atoms of different elements can combine to form compounds
• Billiard ball model
Thomson
• UPDATE: not a solid sphere, there are parts that are negatively charged electrons. Subatomic particles.
• Plum pudding model - negative electrons embedded in positive sphere
Rutherford
• UPDATE: electrons aren't embedded in positive mass. Atoms' masses exist
within the nucleus of the atom - densely packed positively charged center of
atoms. Electrons orbit outside nucleus, taking up space
• Gold foil experiment
• Planetary model; nuclear atom
Now, atoms can be seen and manipulated using inventions such as the scanning
electron microscope.
Atomic number = number of protons
• Identifies one element from another
• Also gives number of electrons on a neutral atom
Mass number = total mass of the atom (amu)
• Protons + neutrons
Isotopes - different # neutrons but same protons
Isotope symbol:
Upper left - mass #
Lower left - atomic # (smaller #, only protons)
Name. Symbol. Atomic #. Mass #. Protons. Neutrons. Electrons. Isotope
Symbol
Carbon.
Hg.
37.
W.
54.
14
200
86
138.
183
131
56
Atomic mass = weighted average of the naturally occurring isotopes
• Atomic mass IS NOT THE SAME AS mass number!!!
• Mass numbers are whole numbers, sum of protons and neutrons
• Atomic numbers are averages so can be decimals and are found on the
periodic table underneath element symbol
• Atomic mass is usually closest to the most abundant natural isotope
Atomic mass calculation:
Atomic mass = (% natural abundance of A)(mass number of A) + (% natural
abundance B)(mass number of B) + (% natural abundance C)(mass number of C)
+ ...