Review for chapter 5 test

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The five Statements of Dalton’s Atomic Theory

 

 

  1. *(An element is composed of tiny, indivisible, indestructible particles called atoms.)*
  2.   *(All atoms of an element are identical and have the same properties.)*
  3. Atoms of different elements combine to form compounds.
  4.  Compounds contain atoms in small whole number ratios.
  5.   Atoms can combine in more than one ratio to form different compounds.

 

*(proven not to be true)*

Thomson’s Contribution to Atomic Theory

 


Thomson visualizes electrons in homogeneous spheres of positive charge in a way that was analogous to raisins in English plum pudding. Thus, the Thomson proposal became popularly known as the plum pudding model or raisin pudding model of the atom.

Understanding Rutherford’s Experiment

 


In 1906, Rutherford found that alpha rays contained particles identical to those of helium atoms stripped of electrons. He experimented with alpha rays by firing them at thin gold foils. As expected, the particles passed straight through the foil or, on occasion, deflected slightly. 

Table 5.1 Subatomic Particles

Subatomic

Particle

 

Symbol

 

Location

 

Relative Charge

 

Relative Mass

electron

e-

Outside nucleus

 -1

1/1836

Proton

p+

Inside nucleus

+1

1

neutron

n^o

Inside nucleus

  0

1

Isotopes: Atoms of the same element that have a different number of neutrons in the nucleus are isotopes. 


Atomic

Notation

Atomic

Number

Mass

Number

Number

Of Protons

Number of

Neutrons

Number of

Electrons

 

  5

11

5

6

5

 

7

15

7

8

7

 

20

40

20

20

20

 

80

200

80

120

Calculation of Atomic Mass

Example exercise 5.3

Light travels at a constant speed in a vacuum. The velocity of light is constant, as all wavelengths and frequencies travel at 3.00 x 10^8 m/s.

 Frequency: refers to the number of wave cycles completed in each second.


Wavelength: refer to the distance the light travels to complete one cycle.


The term light usually refers to radiant energy that is visible.What we orinarily observe as white light is actually several colors of light mixed together. When white light passes through a glass prism, it separates into all the colors of the rainbow, that is, red, orange, yellow, green, blue, and violet.  

Figure 5.9

Bohr Model of the Hydrogen Atom: The electron is a specific distance from the nucleus and occupies an orbit of discrete energy. According to the Bohr model, the electron is found only in a given energy level.

 

Hydrogen Emission Spectrum: An emission line spectrum is produced when hydrogen gas is excited by an electrical voltage. After the emitted light is passed through a prism, three discrete vivid lines are odserved.

 

Spectral Lines and Energy Levels in Hydrogen: When an eletron drops from energy level 5 to 2, a violet photon is released. When an electron drops from level 4 to 2, a blue-green photon is released; from level 3 to 2, a red photon is released. A visible spectral line corresponds to a large number of identical photons. 

Figure 5.13

A cross section of an Atom: The first energy level has one sublevel (1s). the second energy level has two sublevels (2s and 2p). the third energy level has three sublevels(3s, 3p, and 3d). Although the diagram suggests electrons travel in circular orbits, this is a simplification and is not actually the case.

 

Table 5.3

Energy             Energy             Maximum e-                Maximum e- IN

Level               Sublevel            Sublevel                      energy Level

 

1                      1s                     2e-                               2e-

2                      2s                     2e-                              

                        2p                    6e-                               8e-

3                      3s                     2e-                              

                        3d                    10e-                             18e-

4                      4s                     2e-

                        4p                    6e-                              

                        4d                    10e-                            

                        4f                     14e-                             32e-

To find the maximum number of electrons in a main energy level: we add up the electrons in each sublevel. The first energy level has one s sublewvel; it can contain only 2e-. The second major energy level has two sublevels, 2s and 2p. the 2s can hold 2e- and the 2p can hold 6e-. Thus, the second energy level can hold a maximum of 8e-. 

Figure 5.16


                              7s^2  7p^6

 

                              6s^2  6p^6 6d^10

                              5s^s  5p^6  5d^10  5f^14

                              4s^2  4p^6  4d^10  4f^14

                              3s^2  3p^6  3d^10

                              2s^2  2p^6

                              1s^2

Eletron Configuration: Use the atomic number of the element combine with the distribution of electrons by energy level to write the configuration of an electron. 
Figure 5.17, 5.18

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