# Atomic Theory

Topics: Atom, Electron, Neutron Pages: 8 (1717 words) Published: January 1, 2013
Assignment: Atomic Theory

1. Write the complete symbol and determine the no. of electrons, protons and neutrons of the following
e-p+n
a.) Oxygen-88
b.) Cesium-5555
c.) Argon-1818
d.) Uranium-9292
e.) Copper-2929

2. Calculate the atomic mass of sulfur from its natural isotope. f.) Sulfur-36
g.) Sulfur-32
h.) Sulfur-33
i.) Sulfur-34

3. Complete this table.
Symbol of Elements| Atomic Number| Atomic Mass| # of protons| # of Electrons| # of Neutrons| Sc| 21| | 21| 21| 24|
Zn| 30| | 30| 30| 34|
Br| 35| | 35| 35| 44|
Ba| 56| | 56| 56| 82|

4. Fill in the gaps in the following table.
Symbol| 102Ru3+| Se| Os| I| Ce|
p+| 44| 34| 76| 53| 58|
no| 58| | | | |
e-| 41| | | | |
Net charge| positive| | | | |

5. How does Dalton’s atomic theory account for the fact that when 1.000 g of water is decomposed into its elements, 0.111 g of hydrogen and 0.889 g of oxygen are obtained regardless of the source of the water?

*Using Dalton's theory, it is said that he atoms of elements combine in constant ratios to form compounds. Regardless of the water source, when the water was decomposed to its elements, there is really a constant ratio between the two elements composing the water.

6. Summarize the evidence used by J.J Thomson to argue that cathode rays consist of negatively charged particles?
* After observing that the beam of light in the cathode ray tube is attracted to a positive charge and repelled by a negative charge, it is concluded that the rays consist of a stream of small, electrically negatively charged particles.

*The cathode rays were deflected from their straight line path by both electric and magnetic fields. The direction of deflection also shows that they are negatively charged particles.

7. a.) What is the purpose of the X-ray source in the Millikan oil-drop experiment.
* He used X-ray to ionize gas molecules in the chamber. Electrons from this ionization process adhered to the oil process. The oil droplets now carry a negative charge.

b.) What do you think would be the effect on the rate of oil drops descending if the charges on the plates were reversed (negative above positive)?
*The oil will not drop. They would stay up with the negative plate.

8. a.) What are the main subatomic particles that make up the atom?
*The main subatomic particles that make up an atom are protons, neutrons and electrons.

b.) What is the charge, in units of the electronic charge, of each of the particles?
* Electron : A negative particle. It has a unit negative charge (-1).
*Protons : These are positive particles. They have a unit positive charge (+1).
* Neutrons : These are neutral particles. Neutrons with protons provide mass to an atom.

c.) Which of the particles is the most massive? Which is the least massive?
*The neutrons are the most massive. Electrons are the least massive.

9. How many protons, neutrons, and electrons are in the following atoms:
e-p+n
a.) Si – 28 1414 14
b.) Ni-6028 28 32
c.) Rb-85 37 37 48
d.) Xe-128 54 5474
e.) Pt-195 78 78 117
f.) U-238 92 92 146

10. a.) The gamma rays are not deflected by an electric field. What can we conclude about gamma radiation from this observation?
* Gamma rays are photons of light and therefore do not have a charge. A magnetic field will only defect objects that have a charge and are moving or are magnetic.

b.) Why are alpha and beta rays deflected in opposite directions by an electric field?
*Alpha rays consist of positively charged helium nuclei. Beta rays consist of negatively charged electrons. A magnetic field will apply a force to a moving charged particle. Positively charged particles are accelerated in one direction and negative charged particles are accelerated in...