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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