Notes Chapter 4: The Structure of the Atom
Name: ____________________________ Period: __________ Date: ________
Notes Chapter 4: The Structure of the Atom
4.1 Early Theories of Matter
A. The Philosophers - believed matter was made of earth, water, air, and fire.
1. Democritus (460-370 BC) was the first to propose that matter was made up of tiny _________________ he called atomos, which could not be further ______________________.
a. Without being able to experiment, he could not __________ his ideas, and they were ______________.
B. John Dalton (1766-1844) – began the development of the modern ________________ theory.
1. Dalton’s Atomic Theory- 1803
a. All matter is made up of _________________.
b. Atoms of ______________ element are______________________ and are different from those of other elements.
c. Atoms cannot be ________________, divided, or _______________.
d. Different atoms __________________ in certain ratios to form ______________________.
e. In chemical reactions atoms are ___________________, combined, or __________________.
2. Dalton was able to perform _______________________, observe many _________________ reactions, and determine the mass _____________ of elements to verify his theories.
C. Defining the Atom
1. Atom- the smallest particle of an ____________________ that retains the __________________of the element.
2. How big is an atom? consider this:
world population in 2000: 6,000,000,000
# of atoms in a single copper penny:
29,000,000,000,000,000,000,000 or ______ x __________
3. Nanotechnology – molecular manufacturing which is the atom-by-atom building of ___________________ the size of _____________________.
4.2 Subatomic Particles and the Nuclear Atom subatomic particles make up ______________.
A. Discovering the Electron
1. Cathode Ray Tube - Glass ___________________ tube from which ________ was removed. a. metal electrodes at each end - _________________ is the negative end, anode is the _____________________ end
2. Cathode Ray - a ray of __________________ that originates from the cathode and travels to the ______________ of a cathode ray tube
a. led to the invention of ____________________ and computer monitor images – formed as radiation from the cathode strikes ______________-producing chemicals that coat the backside of the __________________.
3. By end of the 1800s scientists concluded that
a. No matter what the ___________ was in the tube or what the electrodes were _________ of, the cathode ray was _________________ which meant that these __________________ particles were in ________ matter.
b. since the particles were attracted to the positive anode, they must be ___________________.
c. The ray deflected toward a _________________ which means it was made of _____________________ and not just a stream of light.
4. Electrons – _________________________ charged particles.
5. J.J. Thomson (1856-1940) – discovered the first subatomic particle, the _________________ by determining the mass-to-charge ratio of the particle.
a. Determined that the _________ of the charged particle was _______ than that of smallest element, ________________________________.
b. Meant that atoms were made of _________________ particles, disproving part of Dalton’s theory.
c. ___________________ Plum-pudding / Chocolate-chip cookie dough model of the atom – proposed that negatively charged ___________________ (chips) were distributed through a “dough” of ______________________________ charge.
7. Robert Millikan (1868-1953) – 1909 determined that an electron has a ____________________ charge. - 1 (e-)
B. The Nuclear Atom
1. Ernest Rutherford (1871-1937) – discovered existence of ___________.
a. used a gold foil experiment to see if positive alpha particles would be __________________ by the ________________ in the atom.
b. Since the ___________________ charge was thought to be ___________________ out, he thought it would not alter the path of the alpha particles.
c. Amazingly some were deflected at ______________ angles which meant there must be a concentrated __________________ area.
2. Nuclear Model – An atom was mostly _______________ space through which the electrons move with a tiny ____________ region called the ______________________ in the center.
3. Nucleus- dense region in ___________________ of atom which is positively charged and contains virtually all of its ____________.
4. Neils Bohr (1885 – 1962 ) Electrons ___________ the nucleus.
a. orbits have a set _______ and energy.
b. Lowest energy is the ___________ orbit.
c. n = _____________ number or energy level.
d. Radiation (energy) is ______________ or absorbed when an ____________ moves from one orbit to another.
e. We see the emitted ______________ as light or photons.
f. the photons travel at different ____________________ which we see as different __________
5. BUT there was still more ___________ than could be explained by the protons.
C. Completing the Atom- The Discovery of Protons and Neutrons
1. Rutherford refined the concept of the nucleus to include _________________ and __________________.
2. Proton- subatomic particle carrying a _______________ charge +1 (p+)
3. James Chadwick (1932) – showed that the nucleaus also contained another subatomic particle.
4. Neutron- has a mass nearly ____________to a proton, but carries _______ charge (neutral) (n0)
4. Atoms are electrically _____________ meaning
the number of ____________ = the number of ___________________.
4.3 How Atoms Differ
~ Each Element is made of ________ type of atom. There are 92 natural elements, so there are 92 different kinds of ______________.
~ The atoms _____________ in the number of electrons, protons, and neutrons.
A. Atomic Number - the number of ____________________ in an atom.
1. The periodic table is organized left to right and top to bottom by _______________________ atomic number
2.Atoms are neutral and that the number of protons = the number of electrons. So the atomic number will give you the number of ___________________ AND ________________________!!
Atomic number = # protons = # electrons
B. Isotopes and Mass Number
1. While the number of protons must ______________ the number of electrons, the number of __________________ may differ.
2. Isotope - atoms with ______________number of protons but different numbers of _________________________.
EX: Potassium (K) has 3 isotopes. All three have ______ protons and electrons, but one has _______ neutrons, one has _____ neutrons, and one has _________ neutrons.
3.Mass Number – is the sum of the number of _________________ and ______________________ in the nucleus.
Mass Number = # protons + # neutrons
Mass Number – # protons = #neutrons
4. Isotope Identification - the _____________ number is added after an element’s ___________________ to identify the isotope.
EX: Neon-22, Chlorine-35, Uranium-238
5. Symbolic Notation - Shortened type of notation for an element using the chemical ______________, atomic number, and the __________ number.
The 3 naturally occurring potassium isotopes
|Isotopes ( |Potassium-39 |Potassium-40 |Potassium-41 |
|Protons | |19 |19 |
|Electrons |19 | |19 |
|Neutrons |39-19 = 20 |40-19 = 21 |41-19 = _______ |
|Symbolic notation | | |K-41 |
C. Mass of Individual Atoms
1. Atoms have extremely ________________ masses which are hard to work with, so scientists use a _____________________ for comparison
2. Standard used is a ___________________________ atom
3. Carbon-12 atom has mass of _________ atomic mass units
4. atomic mass unit – one (amu) is nearly ______________ to the mass of 1 proton or 1 neutron.
5. Atomic mass - is the ____________________ average atomic mass of ALL the _______________________ of that element.
D. Calculating Atomic Mass
1. Isotopes of elements exist in nature in _____________________ amounts.
2. Atomic Mass = % _______________________ x atomic mass for each isotope
Then _______ all the atomic masses to get the weighted average atomic mass
Ex: Chlorine:
Isotopes
Chlorine-35 exists at 75% so 35 x .75 = _________ amu
Chlorine-37 exists at 25% so 37 x .25 = ________ amu
Weighted Atomic mass is 26.4 + 8.9 = ________ amu
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