student information
Tuesday 7 May 2013
warning of fraud
hello people of Nigeria,it been true that some candidate are not seeing there result due to unverification of biometric data.And it is unfortunate that half of the candidate did not make up to 180,but please,on no account should you pay your money to any professor or whatever for upgrading,because,u might loose your money,and the admsion as well. NOTE: If you know that u put university of Uyo as your first choice,and second choice and you need information concerning the school,just call me on this number 08069135694, Wish you all the best.in your admision pursuits. GOODLUCK
Monday 11 February 2013
MENDELEEV PERIODIC TABLE
In 1869, just five years after
John Newlands put forward his
Law of Octaves, a Russian chemist called
Dmitri Mendeleev published
a periodic table. Mendeleev also arranged the elements known at the time
in order of relative atomic mass, but he did some other things that made
his table much more successful.
SUB ATOMIC PARTICLES
Introduction
The Bohr Model is out-dated but depicts the three basic subatomic particles in a comprehendible way.
Electron clouds (in the figure shown below) are better representations
of where electrons are found. The darker areas represent where the
electrons will have a higher probability of being located and the
lighter areas represent where they are less likely to be found.
Particle | Electric Charge (C) | Atomic Charge | Mass(g) | Atomic Mass (Au) | Spin |
Protons | +1.6022 x 10-19 | +1 | 1.6726 x 10-24 | 1.0073 | 1/2 |
Neutrons | 0 | 0 | 1.6740 x 10-24 | 1.0078 | 1/2 |
Electrons | -1.6022 x 10-19 | -1 | 9.1094 x 10-28 | 0.00054858 | 1/2 |
- Au is the SI symbol for atomic mass unit.
- As you can see the positive charge of protons cancels the negative charge of the electrons, and neutrons have no charge.
- In regards to mass, protons and neutrons are very similar, and have a much greater mass than electrons. In calculating mass, electrons are often insignificant.
- Spin is the rotation of a particle. Protons, neutrons, and electrons each have a total spin of 1/2.
Protons
Protons were discovered by Earnest
Rutherford in the year 1919, when he performed his gold foil experiment.
He projected alpha particles (aka Helium nuclei) at gold foil and the
positive alpha particles were deflected. He concluded that protons exist
in a nucleus and have a positive nuclear charge. The atomic number or
proton number is the number of protons present in an atom. The atomic
number determines an element (e.g., the element of atomic number 6 is
Carbon).
Electrons
Electrons were discovered
by Sir John Joseph Thomson in 1897. After many experiments of
cathode-rays, J.J. Thomson demonstrated the ratio of mass to electric
charge of cathode-rays. He confirmed that cathode-rays are fundamental
particles that have a negative charge. Cathode-rays became known as
electrons. Robert Millikan, through oil-drop experiments, found the
value of the electronic charge.
Electrons are located in
an electron cloud, which is the area surrounding the nucleus of the
atom. There is usually a higher probability of finding an electron
closer to to the nucleus of an atom. Electrons can abbreviated as e-.
Electrons have a negative charge that is equal in magnitude to the
positive charge of the protons. However, their mass is considerably less
then that of a proton or neutron (such that it is usually
insignificant). Unequal amounts of protons and electrons creates ions
that can either be positive cations or negative anions.
Neutrons
Neutrons were discovered
by James Chadwick in 1932, when he demonstrated that penetrating
radiation incorporated beams of neutral particles. Neutrons are located
in the nucleus with the protons. Along with protons, they make up almost
all of the mass of the atom. The number of neutrons is called the
neutron number and can be found by subtracting the proton number from
the atomic mass number. The neutrons in an element affect which isotope the atom is of, and often times, its stability. The number of neutrons does not have to equal that of the protons.
Identification
Both of the following are appropriate ways of representing the composition of a particular atom.Example |
Template:ExamplseEnd
Every element has a specific number of protons, so the proton number is not always written (eg. second method of writing).
- # Neutrons = Atomic Mass Number - Proton Number
- Atomic Mass Number is abbreviated as A.
- Proton Number(or Atomic Number) is abbreviated Z.
- # Protons = Proton Number or Atomic Number
- In Neutral Atoms, # Electrons = # Protons
- In Ions, # Electrons = # Protons - (Charge)
- Charge is written with the number before the positive or negative sign
- Example, 1+
Other Basic Atomic Particles
Many of these particles (explained in detail below) are emitted through radioactive decay. Click Here for More Information. Also note that many forms of radioactive decay emit gamma rays, which are not particles.
Alpha Particles
Alpha particles can be denoted by He2+,α2+, or just α.
They are helium nuclei which consist of two protons and two neutrons.
The net spin on alpha particles is zero. They result from large unstable
atoms through a process called alpha decay.
Alpha decay is the process when an atom emits an alpha particle and
loses two protons and two neutrons, therefore becoming a new element.
This only occurs in elements with largely radioactive nuclei elements.
The smallest noted element that emitted an alpha particle was element
52, Tellurium. Alpha particles are generally not harmful. They can be
easily stopped by a single sheet of paper or by one's skin. However,
they can cause considerable damage to the insides of one's body. Some
uses of alpha decay are as safe power sources for radioisotope
generators used in artificial heart pacemakers and space probes.
___________________________________Alpha Decay
Beta Particles
Beta particles (β) are
either free electrons or positrons with high energy and high speed, that
are emitted through a process called beta decay. Positrons have the
exact same mass as an electron but have a positive charge. There are two
forms of this: one that emits electrons and one that emits positrons.
Beta particles, which are 100 times more penetrating than alpha
particles, can be stopped by household items like wood or an aluminum
plate or sheet. Beta particles have the ability to penetrate living
matter and can sometimes alter the structure of molecules that are
struck. The alteration usually is considered as damage, and can be as
severe as cancer and death. In contrast to beta particle's harmful
effects, they can also be used in radiation to treat cancer.
Electron emission may
result when excess neutrons make the nucleus of an atom unstable. As a
result, one of the neutrons decays into a proton, electron, and anti-neutrino.
While the proton remains in the nucleus, the electron, and
anti-neutrino are emitted. The electron can be called a beta particle.
The equation is shown below.
10n -> 11p+ + e- + νe
- n = Neutron
- p+ = Proton
- e- = Electron (Beta Particle)
- νe = anti-neutrino
β- Decay
Beta+(β+) or Positron Emission
Position emission may occur when an excess of protons makes the atom unstable. In this process, a proton is converted into a neutron, positron, and neutrino. While the neutron remains in the nucleus, the positron and the neutrino are emitted. The positron can be called a beta particle. The equation is shown below.
11p+ -> 10n + e+ + νe
- n = Neutron
- p+ = Proton
- e+ = Positron (Beta Particle)
- νe = Neutrino
β+ Decay
Outside Links
- Basic Sub-Atomic Particles: http://www.youtube.com/watch?v=lP57g...eature=related
- Alpha Particles: http://en.wikipedia.org/wiki/Alpha_decay
- Beta Particles: http://en.wikipedia.org/wiki/Beta_particle
- What are Sub-Atomic Particles?: http://www.youtube.com/watch?v=uXcOqjCQzh8
- Atomic Number and Mass Number: http://www.youtube.com/watch?v=lDo78hPTlgk
References
- Petrucci, Ralph, William Harwood, Geoffrey Herring, and Jeffry Madura.General Chemistry. 9th ed. Upper Saddle River, New Jersey: Pearson Prentince Hall, 2007.
- Haskin, Larry A. The Atomic Nucleus and Chemistry; D. C. Heath and Company: Lexington, MA, 1972; pp. 3-4, 43-53.
- Petrucci, Ralph, F. Geoffrey Herring, Jeffrey D. Madura, and Carey Bissonnette. General Chemistry. 10th ed. Upper Saddle River, New Jersey: Pearson Education, Inc., 2011.
Problems
1. Identify the number of protons, electrons, and neutrons in the following atom.
2. Identify the subatomic
particles(protons, electrons, neutrons, and positrons) present in the
following: (Periodic Table will be necessary)
- 146C
- α
- 35Cl-
β+
β-
- 24Mg2+
60Co
3H
- 40Ar
n
- Charge +1, 3 Protons, Mass Number 6.
- Charge -2, 7 Neutrons, Mass Number 17.
- 26 Protons, 20 Neutrons.
- 28 Protons, Mass Number 62.
- 5 Electrons, Mass Number 10.
- Charge -1, 18 Electrons, Mass Number 36.
4. Arrange the following Elements in order of increasing (a) number of protons; (b) number of neutrons; (c) mass.
27Co, when A=59; 56Fe, when Z=26;
11Na, when A=23; 80Br, when Z=35; 29Cu, when A=30; 55Mn, when Z=255. Fill in the rest of the table with your knowledge of the relationships between subatomic particles.
Atomic Number | Mass Number | Number of Protons | Number of Neutrons | Number of Electrons |
2 | 2 | |||
23 | 11 | |||
15 | 16 | |||
85 | 37 | |||
53 | 74 |
1. There are 4 Protons, 5 Neutrons, and 4 electrons. This is a neutral Beryllium atom.
2. Identify the subatomic particles present in the following:
- 146C
- 6 Protons, 8 Neutrons, 6 Electrons
- There are 6 protons in accordance to the bottom proton number. There are 6 Electrons because the atom is neutral. There are 8 Neutrons because 14-6=8. 14 is the atomic mass number which is the superscript above the C.
- 6 Protons, 8 Neutrons, 6 Electrons
- α
- 2 Protons, 2 Neutrons, 0 Electrons
- This is an alpha particle which can also be written as 4He2+. There are two protons because the element is helium. There are no electrons because 2-(2) = 0. There are 2 neutrons because 4-2=2.
- 2 Protons, 2 Neutrons, 0 Electrons
- 35Cl-
- 17 Protons, 18 Neutrons, 18 Electrons
- This
is a Chloride ion. According to the periodic table, there are 17
Protons because the element is Chlorine. There are 18 electrons because
of the negative charge. 17-(-1) = 18. There are 18 Neutrons because
35-17=18.
- This
is a Chloride ion. According to the periodic table, there are 17
Protons because the element is Chlorine. There are 18 electrons because
of the negative charge. 17-(-1) = 18. There are 18 Neutrons because
35-17=18.
- 17 Protons, 18 Neutrons, 18 Electrons
- β+
- 0 Protons, 0 Neutrons, 0 Electrons, 1 Positron
- This is a Beta+ particle. This can also be written as e+. "e" represents an electron, and when it has as postivie charge it is a positron. There is thus one positron
- 0 Protons, 0 Neutrons, 0 Electrons, 1 Positron
- β-
- 0 Protons, 0 Neutrons, 1 Electron
- This is a Beta- particle. This can also be written as e-. This is the standard electron. There is one electron.
- 0 Protons, 0 Neutrons, 1 Electron
- 24Mg2+
- 12 Protons, 12 Neutrons, 10 Electrons
- This is a Magnesium Ion. There are 12 protons from the Magnesium atom. There are 10 electrons because 12-(2) = 10. There are 12 neutrons because 24-12 = 12.
- 12 Protons, 12 Neutrons, 10 Electrons
- 60Co
- 27 Protons, 33 Neutrons, 27 Electrons
- The Cobalt atom has 27 protons as seen in the periodic table. There are also 27 electrons because the charge is 0. There are 33 neutrons because 60-27 = 33.
- 27 Protons, 33 Neutrons, 27 Electrons
- 3H
- 1 Protons, 2 Neutrons, 1 Electrons
- There is 1 Protons because of the Hydrogen element. There is 1 electron because the atom is neutral. There are 2 Neutrons because 3-1 = 2.
- 1 Protons, 2 Neutrons, 1 Electrons
- 40Ar
- 18 Protons, 22 Neutrons, 18 Electrons
- There are 18 Protons from the Argon element. There 18 electrons because it is neutral, and 22 Neutrons because 40 - 18 = 22.
- 18 Protons, 22 Neutrons, 18 Electrons
- n
- 0 Protons, 1 Neutrons, 0 Electrons
- This is a free neutron denoted by the lower case n. Therefore, it is a lone particle, and there is one neutron.
- 0 Protons, 1 Neutrons, 0 Electrons
- Charge +1, 3 Protons, Mass Number 6.
- 3 protons, 3 Neutrons, 2 Electrons
- Charge -2, 8 Neutrons, Mass Number 17.
- 9 Protons, 8 Neutrons, 7 Elecetrons
- 26 Protons, 20 Neutrons.
- 26 Protons, 20 Neutrons, 26 Electrons
- 28 Protons, Mass Number 62.
- 28 Protons, 34 Neutrons, 28 Electrons
- 5 Electrons, Mass Number 10.
- 5 Protons, 5 Neutrons, 5 Electrons
- Charge -1, 18 Electrons, Mass Number 36.
- 17 Protons, 19 Neutrons, 18 Electrons
a) Na, Mn, Fe, Co, Cu, Br
- Z=#protons;
- Na: z=11; Mn: Z=25, given; Fe: Z=26, given; Co: Z=27; Cu: Z=29; Br: Z=35, given
- A=#protons+#neutrons, so #n=A-#protons(Z);
- Na: #n=23-11=12; Cu: #n=59-29=30; Fe: #n=56-26=30; Mn: #n=55-25=30; Co: #n=59-27=32; Br: #n=80-35=45
c) Na, Mn, Fe, Co, Cu, Br
- Na: 22.9898 amu; Mn: 54.9380 amu; Fe: 55.845 amu; Co: 58.9332 amu; Cu: 63.546 amu; Br: 79.904
5. Fill in the rest of the table with your knowledge of the relationships between subatomic particles.
Atomic Number | Mass Number | Number of Protons | Number of Neutrons | Number of Electrons |
2 | 4 | 2 | 2 | 2 |
11 | 23 | 11 | 12 | 11 |
15 | 31 | 15 | 16 | 15 |
37 | 85 | 37 | 48 | 37 |
53 | 127 | 53 | 74 | 53 |
ATOMIC AND MOLECULAR PHYSICS
Subscribe to:
Posts (Atom)