ATOM
a. Elementary particles: particles forming the atom consists of electrons, protons neutrons den.
1. Proton: atom forming particles that have mass equal to one sma (amu) and charged +1.
2. Neutron: particles forming a sma atomic mass (amu) and neutral.
3. Electron: atom forming particles that have no mass and charged -1.
b. The nucleus: a positively charged nucleus, consisting of protons neutrons den.
c. Notation elements: zA A to X: sign atoms (elements)
Z: atomic number = number of electrons (e)
= Number of protons (p)
A: mass number = number of protons + neutrons
In neutral atoms, applies: the number of electrons = number of protons.
d. No neutral atoms: electrically charged atoms due to excess or deficiency of electrons when compared with the neutral atom.
Positively charged atoms when the electron deficiency, called cations.
Negatively charged atoms when an excess of electrons, called anions.
example:
- Na +: cation with one electron deficiency
- Mg2-: cation with a shortage of 2 electrons
- Cl-: anion with an excess of one electron
- O2: anion with an excess of two electrons
e. Isotopes: elements of the same atomic number, but different mass numbers.
Example: oxygen isotopes: 816 O; 817 O; 818 O
f. Isobar: elements of the same mass number, but different atomic numbers.
Example: 2759 2859 CO with Ni
g. Isoton: elements with the same number of neutrons.
Example: 613 C to 714 N
h. Iso electron: atom / ion with the same number of electrons.
Example: Na + with Mg 2 +
K + with Ar
HISTORY AND DEVELOPMENT OF ATOMIC THEORY
From the times of the ancient Greeks to the present, the model and the atomic theory continues to evolve. Through the model and theory of the atom, we can determine the structure of an atom.1. Mr. Democritus and Aristotle
From the times of the ancient Greeks to the present, the model and the atomic theory continues to evolve. Through the model and theory of the atom, we can determine the structure of an atom.1. Mr. Democritus and AristotleThe above picture is the father of Greek genius of expression on the definition of atoms for the first time, the first, circa 460-370BC.Democritus father's opinion about the atomatoms are the elements that make up reality. However, these elements can not be divided lagi.Karena that these elements are named atom. Atom comes from the Greek atomos: a means and Tomos mean divided.
According to Aristotle a substance composed of fire, water, earth, and air. So who is more right? It must depend on the people who receive it at that time. Apparently the theory of Mr. Aristotle was more widely accepted and used as the basis for the next developmental theorizing by Dalton.2. ATOM THEORY OF DALTONFor a thousand years the term atom sink, like everyone is convinced that what Aristotle says is the truth that has been searched on "whether the material is composed of a substance? '. But apparently in 1803 there was a high school teacher in the UK who are still curious about the atom. By basing on the theory of Aristotle, on a sunny afternoon, Dalton had discovered evidence and the fundamental ideas of the theory. This theory is also able to explain the law of conservation of mass Law of Lavoisier and Proust fixed ratio.Here are 5 Atomic Theory Dalton:1. The elements consist of particles remarkable little that can not be subdivided (called atoms) and a massive round ball shape. In a chemical reaction, they can not be created, destroyed or converted into other types of elements.2. All atoms in the same element are similar and therefore have similar properties, such as mass and size.3. Atoms of different elements types have different properties as well.4. Compounds can be formed when more than one type of element combined.5. Atoms of two or more elements can be reacted in different ratios to produce more than one type of compound.But times were different then Democritus time to time, so many scientists are trying to find a way to the term "fault" of the theory of Dalton. Dalton was still confident. Before anyone finds evidence that his theory was wrong, he thought that his theory is that terbenar.Apparently there finally two scientists who disagree with the Atomic Theory Dalton. They are Sir Humphry Davy (1778-1892) and Michael Faraday (1791-1867). To prove that their opinion is more correct, they are doing experimental chemical change when an electric current passing through an electrolyte solution, or so-called electrolysis. So amazing, Faraday discovered that the amount of a substance produced in the electrolysis current electrodes is proportional to the amount of electrical current. In 1833, Faraday also discovered that the amount of electricity required to produce 1 mole of substance at the electrode is fixed (96.500 C). This relationship is known as Faraday's law of electrolysis. Based on his opinion of a chemist, so he concludes that there is a basic unit in the electrolysis, there are analogous to electricity. He also gave the name of the electrons in this hypothetical unit.Since then several statements Dalton's atomic theory was killed. Weakness Dalton's atomic theory. In Dalton's atomic theory is not explained the source of the charge for electricity according to Dalton when atoms are neutral particles. The surplus is Dalton chemistry provides the basis for what is an atom.3. ATOM THEORY THOMSON
The inventor of the electron, Mr. J.J. ThomsonAfter Dalton's atomic theory disqualified because there was a question no one has answered it, then Thomson was in about the 1890's trying to do an experiment to find a way out of the problem. The basis of theories of other scientists such as Humphry Davy, who proved that the gas becomes a better conductor of electricity at low pressure, Thomson also conducted experiments using a cathode ray tube. So this is a tube under vacuum tubes, and at each end of the tubes were
Cathode ray tube voltage electrical current is high enough, it turns on the low pressure and high temperature, the gas in the fluorescent tube will depend on the type of substances in the tube. If the gas pressure is reduced, the front area of the cathode will be dark. The area is growing dark when the gas pressure continues to be reduced. Finally, the entire tube to be dark, but the front of the cathode tube glow with a greenish tint. Through experiments, it can be proved that it was a greenish color particle radiation. Because it comes from the cathode, the beam called cathode rays.Further experiments proved that cathode rays are electrically charged particle radiation negatively hereinafter called electrons.1. Cathode rays propagate straight from the anode towards the cathode surface2. Cathode rays can rotate turbines3. Cathode rays are deflected towards the positive pole"Atom is a ball of solid positively charged and negatively charged electrons scattered didalamya" This is the conclusion of the Thomson theory.
illustration thomson atomic theoryExcessProving the existence of other negatively charged particles in atoms. Means the atom is not the smallest part of an element.WeaknessThomson's model can not explain the arrangement of positive and negative charges within the atomic sphere, can not explain the chemical reactions that occur between atoms
4. Rutherford Atomic Theory
Rutherford, the discoverer of the atomic nucleus in collaboration with Thomson
After Thomson proposed his theory in 1910 was no less Rutherford conducted experiments to reveal his version of the theory. With the assistance of two of his disciples, they experiment known as the scattering of alpha rays, which are positively charged particles, and moving forwards, great power that can penetrate through a thin sheet of paper.
The experiment is actually intended to test Thomson opinion of whether the atom is really a solid ball when it is positive that the alpha particles would be reflected or deflected. From their observations, obtained the fact that when alpha particles were fired at a very thin gold plates, then most of the alpha particles passed (no deviation angle less than 1 °), but from observations obtained Marsden fact that one in 20,000 alpha particles will turn angle of 90 ° even more, or there reflected. This is not in accordance with the theory pastialh Thomson which are atoms depicted dense homogeneous in all its parts.
Based on the experimental genius Rutherford suggested that his idea of the atomic nucleus. According to him, most of the mass of the atom and the positive charge is concentrated at the center of the atom, hereinafter referred to circulate around the core atom.Elektron at distances relatively far away. The distance between the nuclei of atoms until the skin is called the atomic radius.With such a model, the scattering of alpha rays thin gold plates can be explained as follows:1. Most of the particles because the alpha rays can penetrate through sterile areas2. Alpha particles are deflected by the nuclei approach mengalani repulsive core3. Alpha particles towards the nuclei is reflected by the positively charged nucleus and a very solid
"Atomic nuclei are composed of very small and positively charged, surrounded by negatively charged electrons. "So this is the conclusion of how atoms form meurut Rutherford.ExcessHypothesized that atoms are composed of atomic nuclei and electrons that surround the nucleusWeaknessCan not explain why the electrons do not fall into the nucleus. Based on the theory of physics, the motion of electrons around the nucleus is accompanied by transmitting energy so long - eventually the electron energy is reduced and the longer the trajectory will approach the core and falling into the nucleus Take a piece of string and tie one end of your piece of wood while you hold the other end. Rotate the rope over your head. What happened? Right. Eventually the rotation will slow and will hit your head because your rotation is weak and sore holding the rope. Since Rutherford was already introduced trajectory / position of electron later called skin
5. Niels Bohr theory of the atom
Niels Bohr introduced the theory of electron trajectories
Sure enough everything that exists in this world nothing is perfect. Any theory that scientists issued sure there besides the advantages, there are also drawbacks. In the experiments, tahin 1911, Niels Bohr Rutherford tried to improve the theory by conducting experiments hydrogen atom spectrum.
Then from these experiments Niehl Bohr theory of the atom are:
1. According to him, there are only a certain set of possible orbits for an electron in a hydrogen atom. Orbit is known as the stationary state of motion (settled) electron and a circular path around the core
2. As long as the electrons are in a stationary orbit, the electron energy anyway so there is no energy in the form of radiation emitted or absorbed.
3. Electrons can only move from one stationary orbit to another stationary trajectory. In this transition, a certain amount of energy involved, the amount in accordance with Planck equation, ΔE = hv.
4. Stationary trajectory is allowed to have the scale with certain properties, especially property called angular momentum. The magnitude of the angular momentum is a multiple of h/2Î or nh/2Î , where n is an integer and the Planck constant h
So according to Bohr, electrons surrounding the nucleus in certain paths called the electron shell or energy level of the lowest energi.tingkat shell electron is located at dalam.semakin out of her skin and the greater the number the higher the energy level.
excess
Bohr atom that the atom is made up of several skin for a transfer of electrons.
weakness
atomic model is not able to explain the Zeeman effect and the effect Strack6. ATOM THEORY QUANTUM MECHANICS MECHANICS OR WAVES
Schrodinger
After Niehl Bohr theory it also has weaknesses, subsequent scientists are working to improve Erwin Schrodinger. Based on further development saying that the electron trajectory is not round but like a wave around the nucleus. Therefore, the position can not be known with certainty. Atomic theory of quantum mechanics have in common with the theory of Niels Bohr energy levels or shells, but differ in terms of the trajectory or orbit.
Experiments done is experiment Chadwick
Conclusion The results of the experiment:
sketch of the theory of quantum mechanics
Shows the electron cloud around the nucleus where the probability of an electron. Orbital describes the energy levels of electrons. Orbitals with the same energy level or nearly the same to form sub shell. Some sub leather combine to make such kulit.Dengan skin consists of several sub-skin and consists of several orbital subshell. Although the skin is the same position but not necessarily the same orbital position.
Weakness Modern Atomic Model
Schrodinger wave equation can be applied only exact for particles in a box with a single electron and atom
QUANTUM NUMBERS
1. The principal quantum number (n), worth 1, 2, 3, 4, ... and so on. Quantum numbers are consistent with the electron shells in an atom as usual energy level expressed by the skin. The principal quantum number (n): 1 2 3 4 ... In accordance with the skin to: 1 2 3 4 ...
K L M N ... Thus the principal quantum number indicates the amount of electron trajectories.
2. Azimuthal quantum number (l), value 0, 1, 2, 3, ... (N - 1) quantum number shows in the subshell (sublintasan) where electrons move and also determines the shape of the orbital. subshell l = 0 is also called the orbital s (sharp) subshell l = 1 is also called p orbitals (principle) subshell l = 2 is also called the orbital d (diffuse) subshell l = 3 is also called orbital f (fundamental) Each skin has skin subshell corresponding number, for example: n = 1 (K shell) prices have l = 0, ... (1 - 1) = 0 Skin to-1 (K) has a subshell, the subshell l = 0 or 1s n = 2 (L shell) prices have l = 0, ... (2-1) = 0, 1 Skin to-2 (L) has two subshells, namely subshell l = 0 or 2s orbital and subshell l = 1 or 2p orbitals n = 3 (skin M) has a price l = 0, ... (3-1) = 0, 1, 2 Skin for-3 (M) had 3 subshell, namely: subshell l = 0 or 3s orbital subshell l = 1 or 3p orbitals subshell l = 2 or 3d orbitals n = 4 (leather N) has a price l = 0, ... (4-1) = 0, 1, 2, 3 Skin for-4 (N) had 4 subshell, namely: subshell l = 0 or 4s orbital subshell l = 1 or 4p orbital subshell l = 2 or 4d orbital subshell l = 3 or 4f orbitals
when n = 1, then there is only one possible value of the azimuthal quantum number l = 0 for the first shell (K) consists of only one subshell is s subshell. As for n = 2, then there are two possible subshell l = 0 and l = 1 for the second shell (L) there are two subshell is s and p sub shell.
What about the next skin?
Skin M, then the value of n = 3 and l = 0, 1, and 2 as having subshell s, p, and d.
Leather N, then the value of n = 4 and l = 0, 1, 2, and 3 as having subshell s, p, d, and f.
So the value of azimuthal quantum number is not likely equal to or greater than the main quantum number. A maximum value of l = n - 1.
3. Magnetic quantum number (m), precious-l, ..., 0, ... + L This quantum number determines the position or orientation of the orbital, also indicate the presence of one or more energy levels which constitute the level of a subshell. Any price l have a price m. Example:
conclusion:
s orbital (l = 0) has one orbital, the price of the m = 0.
p orbitals (l = 1) has three orbitals, the price of its m: -1, 0, and +1.
d orbitals (l = 2) have 5 orbitals, the price of its m: -2, -1, 0, +1, and +2.
f orbitals (l = 3) have seven orbitals, the price of its m: -3, -2, -1, 0, +1, +2, and +3.
Orbitals in a subshell have a particular form and is located in a particular space anyway.
Based on observations and mathematical calculations of spherical s orbital, meaning: there are electrons in s orbitals are equally far away and all directions of the atomic nucleus. While the p orbitals have a twisted shape like a balloon. P orbitals have 3 orbitals, each of which lies on the axis of x, y, and z that distinguished p orbitals px, py, and pz.
D orbitals have 5 spread between the axis orbital axis space x, y, and z are each divided into dz ², dx ²-y ², DXZ, DXY, and dyz.
4. Spin quantum number (s), worth +1 / 2 and -1 / 2 (possibly turn right = 1/2 and possibly turn left = 1/2).
This quantum numbers give an idea about the direction of rotation of the electron on its axis.
Each has a price s = m + 1/2 and s = - ½
Quantum Numbers Functions
The four quantum numbers are used to indicate the location of the last electron (outer) of an atom. Starting from the location of the atomic shell (principal quantum number), subshell atom (azimuthal quantum number), the location of orbital (magnetic quantum number) to the velocity of the electron (spin quantum number). So that this quantum number is specific in accordance with the principle of prohibition pauli. Next we combine the four quantum numbers to determine the identity of an electron. In order to determine exactly we should understand the electron configuration and orbital diagram first.
For example, the electron configuration and orbital diagram of sulfur (S) as follows:
To determine the quantum numbers of the last electron we just noticed that the outer subshell 3p:
The depiction of the last electron marked in red. Electrons are located on the skin of 3 means the main quantum number (n) = 3. Located in subshell p mean quantum number azimutnya (l) = 1. As for determining the magnetic quantum number we need to name each subshell 3p orbitals in which the numbers are green. According to the diagram above, the value of the magnetic quantum number (m) = - 1. And because the downward arrows mark the spin quantum number (s) = - ½.
