Chapter 4 Structure of the Atom. Section 4.1. Democritus (460-370 BC) Matter is composed of empty space through which atoms move Atoms are solid, homogeneous, indestructible and indivisible Different kinds of atoms have different sizes and shapes
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Subatomic Particles nucleus of the atom. He used an experiment in which he passed alpha particles through a thin film of gold foil. He expected the alpha particles to pass through, but found instead that they were deflected at large angles. He determined that there was a dense positive core in the atom, which he called a nucleus.
The nucleus is the tiny positive core of the atom which contains most of the mass of the atom.
The proton (p+) is the positively (1+) charged particle found in the nucleus of the atom. It has a relative mass of one.
The neutron (no) is the particle with no charge (0) found in the nucleus of the atom. It has a relative mass of one.
The electron (e-) is the negatively (1-) charged particle found in the electron cloud outside of the nucleus. It has very little relative mass by comparison.
ACTUAL MASS (g) nucleus of the atom. He used an experiment in which he passed alpha particles through a thin film of gold foil. He expected the alpha particles to pass through, but found instead that they were deflected at large angles. He determined that there was a dense positive core in the atom, which he called a nucleus.
Obj. 5…Subatomic Particles
PROPERTIES OF SUBATOMIC PARTICLES
9.11 x 10-28
1.67 x 10-24
1.67 x 10-24
(change atomic # = change of element).
** (+) charge = less e- than p+
** (-) charge = more e- than p+
(a.k.a. mass #)
Potassium-39 Potassium-40 Potassium-41
Example: The atomic mass of Chlorine (Cl) is 35.453 amu. Chlorine exists naturally as 75% chlorine-35 and 25% chlorine–37.
.75770 x 34.969 amu = 26.496 amu
.24230 x 36.966 amu = 8.957 amu
Weighted average atomic mass of Cl =
(26.496 + 8.957) = 35.453 amu
avg. of allisotopes that exist in nature.
- abundance of isotope is just as important as mass!
Natural copper (Cu) consists of 2 isotopes ...
Copper - 63 (mass = 62 .930 g/mole)
Copper - 65 (mass = 64 .930 g/mole)
mass x abundance for each isotope
Step 1 :
add the two values from step 1 together
Step 2 :
62 .93 x .69 =
64 .93 x .31 =
+ the isotopes of that element.
MASS CHANGE the isotopes of that element.
ATOMIC # CHANGE