Atoms consist of protons, neutrons and electrons. Protons and neutrons are in the nucleus. While the electrons continue to revolve around the nucleus because of their electrical charge. all electrons are negatively charged (-) and all the positively charged protons (+). while the neutron is electrically neutral. Charged electrons are negatively charged (-) drawn by the positively charged protons (+) in the nucleus.
In this case, all of the atoms in the universe will be positively charged (+) because there is an excess positive charge (+) in the proton. As a result, all the atoms will conflicting with each other.
A. Development of Atomic Theory
The concept proposed by Democritus atoms that are not supported by convincing experimental, so it can not be accepted by beberpa expert science and philosophy.
The development of the concept of atoms scientifically started by John Dalton (1805), and conducted by Thomson (1897), Rutherford (1911), and refined by Bohr (1914)
Experimental results that reinforce the concept of atoms yielding overview parikel arrangement of atoms in the particles. This picture serves to facilitate in understanding the chemical properties of an atom. Preview arrangement of elementary particles in an atom called atomic model.
Atomic Model Dalton
1. Atoms are the smallest part of the material as it can not be divided.
2. Atom is described as a very small sore balls, an element has atoms are identical and different for different elements.
3.Atoms combine to form compounds with integers and simple comparisons. For example, water consists of two hydrogen atoms and oxygen atoms.
4. The chemical reaction is the splitting or merging or rearrangement of atoms, so the atoms can not be created or destroyed
Hypothesis Dalton described the model of the atom as a ball ache as the ball shot put.
2. Thomson Atomic Model
Atom is a round ball charged
positive and spread on the surface
electrons are negatively charged
3. Rutherford Atom Model
Atoms are composed of hollow spheres and eletron nucleus composed of atomic nuclei and electrons that surround it. Positively charged atomic nuclei and atomic mass centered on the nucleus. The downside of Rutherford could 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 emission electron energy decreases and the longer the trajectory will approach the core and falling into the nucleus.
4. Niels Bohr Atom Model
Atoms consist of a positively charged nucleus surrounded by negatively charged electrons in a track.
Electrons can move from one track to another by absorbing or emitting energy electron atomic energy so it will not be reduced. If you move the track to a higher trajectory, electrons will absorb the energy. If switching to a lower orbit, the electron will emit lower energy, the electrons will radiate energy.
Position of the electron-eletron at certain energy levels called electron shells.
5. Model Atomic Model
electron shells are certainly not the position of an electron, but only a likelihood invented it.
B. Know Experiments Atomic Structure
1. Electron
Cathode ray tube experiment was first performed by William Crookes (1875). Results with experiments is found that a beam of light emerging from the cathode into the anode called cathode rays.
George Johnstone Stoney (1891) proposed the name cathode rays yand called "electrons". The downside of stoney can not account for the effect of the differences in the properties of electrons between atoms of an element with atoms in the other elements. Antonine Henri
Beecquerel (1896) found that the light emitted from radioaktof elements that are similar to electrons.
Joseph John Thomson (1897) continued experimentation William Crookes, namely the influence of an electric field and a magnetic field in the cathode ray tube.
The experimental results JJ Thomson showed that cathode rays could be deflected toward the positive pole of the electric field. This proves there is a negatively charged particles in an atom.
The amount of the charge in eletron discovered by Robert Andreww have (1908) through experiments ownership Oil drops as shown below.
Oil sprayed into the tube charged litrik. Due to an attractive force of gravity would precipitate the fall of oil droplets. If the oil droplets are given a negative charge will be attracted to the positive pole of the electric field. From the experimental results obtained ownership and Thomson electron charge and mass of the electron-1 0.
2. Proton
If the mass of the electron 0 shall mean a particle has no mass. But in fact it has a mass of particulate matter that can be measured and the atoms are neutral atoms. Eugene Goldstein (1886) conducted experiments from the gas cylinder that has a cathode, which was given the holes and electric charge.
The experimental results prove that formed when electrons toward the anode, also formed a positive light towards the opposite direction through the hole in the cathode. After trying various gases in the tube, the gas turns hidrogenlah that produces beams of the smallest positive charge both mass and muatanya, so that particles called protons. The mass of a proton = 1 sma (atomic mass units) and the proton charge = +1
3. The nucleus
After the discovery of the proton and electron, Ernest Rutherford conducted a study of gold thin arduous shooting. If the atom consists of a positively charged particles and negatively the alpha rays are fired should not be forwarded / pierce plate so mincullah terms of atomic nuclei. Ernest Rutherford assisted by Hans Geiger and Ernest Marsden (1911) found the nucleus concept is supported by the discovery of X-rays by WC. Rontgen (1895) and the discovery of radioactive substances (1896). Rutherford experiment can be described as follows.
The results of this experiment make Rutherford stated hypothesis that the atom consists of a positively charged nucleus surrounded by negatively charged electrons, so the atom is neutral. The mass of the nucleus is not equal to the mass of protons in the atomic nucleus, so that DAPT predicted that there is another particle in the nucleus of an atom
4. Neutron
Prediction of triggering W. Rutherford Bothe and H. Becker (1930) conducted experiments on atomic nuclei particle bombardment of beryllium (Be) and the resulting high penetrating power of radiation particles.
James Chadwick (1932). It turns out the particles that cause the high penetrating power of radiation is nertal or uncharged and almost equal to the proton mass. These particles called neutrons and denoted
C. Determining Atomic Structure Based on the Periodic Table
1. Drafting Basic Atomic Particles
Atom is the smallest part of an element that still has the properties of that element. The atomic structure describes how the particles in atoms are composed, made up of atoms and atomic nuclei surrounded by electrons scattered in the skin-skin. Can systematically described subatomic particles following.
Most of the atom consists of a vacuum chamber where there is a very small nucleus where mass and positive charge centered and surrounded by electrons are negatively charged. The nucleus is made up of a number of protons and neutrons. The number of protons in the nucleus determines the atomic nuclear charge, while the atomic mass of the core is determined by the number of protons and neutrons. The next three sub-atomic particles (protons, neutrons, and electrons) view of a particular combination of atoms forming the symbol of an element can be written:
X: the symbol of an element
Z: atomic number
A: mass number
2. Understanding the Structure of An Atom
Look at the number of the periodic table. The atomic number is always smaller than the number of mass labih
The atomic number is the number of protons. Because of the nature of a neutral atom, the atomic number is also the number of electrons
Arrangement of electrons in energy levels, always fill the deepest level before filling the outer level
D. Atomic Number and Mass Number
An atom has a mass of distinctive nature and each other. With the discovery of subatomic particles known term atomic number (Z) and mass number (A)
Writing equalizes wave of atoms of element atomic number and mass number.
Where:
A = mass number
Z = atomic number
X = symbol element
Mass Number (A) = number of protons + number of neutrons
Or
Number of neutrons = mass number - atomic number
Atomic number (Z) = number of protons
1. Atomic number (Z)
Atomic number (Z) shows the number of protons (positive charge) or the number of electrons in the atom. The atomic number is characteristic of an element. Because atoms are neutral, the number of protons equal to the number elektronya, so the atomic number also showed the number of electrons. Electron is what will most determine the properties of an element. The atomic number is written slightly downward before the element symbol
2. Mass Number (A)
Electron mass is very small and is considered zero and the mass of the atom is determined by the nucleus of protons and neutrons. The mass number (A) specifies the number of protons and neutrons that make up the nucleus of an atom of an element. The mass number is written slightly upwards before the symbol of the element.
E. Isotopes, Isobar, and Isoton an element
1. Isotope
Isotopes are atoms that have the same number but have different mass numbers
Each isotope of an element have the same chemical properties as the number of valence electrons equal.
Isotopes can be used to determine the relative atomic mass (Ar) atom is based on the isotope abundances and atomic mass of all isotopes
2. Isobar
Isobar is the elements that have an atomic number but different mass numbers together.
3. Isoton
The atoms are different but have the same number of neutrons
F. Determining Valence Electrons
1. Electron Configuration
Configuration (arrangement) of electrons of an atom by atom shells. Each atom can be charged a maximum eletron 2N2, where n is the location of the skin.
Coat the skin starts from the K, L, M, N and so starting from the closest to the nucleus.
Electrons arranged in such a way on their own skins and stuffed maximum capacity of the skin suit. So there is the rest of their electrons can not be accommodated on the skin then placed next to the skin.
2. Valence Electrons
Electrons are involved in chemical bond formation reactions and chemical reactions are electrons in the outer shell or valence electrons.
The number of valence electrons of an atom is determined by the electrons contained in the last shell electron configuration of the atom. Note the table to determine the number of valence electrons
C. QUANTUM NUMBERS
To determine the position of an electron in an atom, used 4
quantum numbers.
1. The principal quantum number (n): realizing the electron trajectories in
atom.
n has a price of 1, 2, 3, .....
- N = 1 corresponds to the K shell
- N = 2 correspond to the L shell
- N = 3 corresponds to the skin M
- And so on
Each skin or any number of energy levels occupied by electrons.
The number of electrons that can occupy maksimmm energy levels
must satisfy the Pauli formula = 2N2.
Example:
skin-to-4 (n = 4) can be occupied by a maximum of electrons = 2 x 42 = 32
electron
2. Azimuthal quantum number (l): indicate sub skin where
electrons that move also shows a sub-skin
compilers of the skin.
Azimuthal quantum number have prices from 0 to (n-
1).
n = 1; l = 0; corresponding K shell
n = 2, l = 0, 1; corresponding L shell
n = 3; l = 0, 1, 2; appropriate skin M
n = 4; l = 0, 1, 2, 3; appropriate skin N
and so on
Sub leather prices vary is given a special name:
l = 0; fit leather sub s (s = sharp)
l = 1; fit leather sub p (p = principle)
l = 2; fit leather sub d (d = diffuse)
l = 3; fit leather sub f (f = fundamental)
3. Magnetic quantum number (m):
realizing the presence of one or
several levels of energy in a sub shell. Quantum numbers
magnetic (m) has a price (-l) to price (+ l).
For:
l = 0 (sub leather s), price m = 0 (having 1 orbital)
l = 1 (p sub shell), price m = -1, O, +1 (have 3 orbitals)
l = 2 (sub skin d), price m = -2, -1, O, +1, +2 (have 5 orbitals)
l = 3 (sub kwit f), price m = -3, -2, O, +1, +2, +3 (have 7
orbital)
4. Spin quantum number (s):
indicates the direction of rotation of the electron
on its axis.
In one orbital, maximum of 2 electrons can circulate and second
This electron spins through the axis in the opposite direction, and
each one is priced spin +1 / 2 or -1 / 2.
Question:
How the four states of the electron quantum numbers 3S1?
Answer:
The four quantum numbers of the electron position can 3S1
expressed as,
n = 3; l = 0; m = 0; s = +1 / 2, or -1 / 2
D. ELECTRON CONFIGURATION
In every atom orbitals are available, but not necessarily
all orbital is filled. How is the electron charge
these orbitals?
Completion of electrons in the orbitals satisfy some rules.
among other things:
1. Aufbau principle: electrons fill orbitals starting with
the lowest energy level and beyond.
Orbital who meet the low energy levels is 1s
followed by 2s, 2p, 3s, 3p, and on and on
made easier following diagram:
Examples of filling electrons in orbitals several elements:
Atom H: has 1 electron, configuration 1s1
Atom C: has 6 electrons, the configuration 1s2 2s2 2P2
Atom C: has 19 electrons, the configuration 1s2 2s2 2P6 3S2 3P6
4S1
2. Pauli principle: not possible in the atom there are two electrons
with the same four quantum numbers.
This means, if there are two electrons that have a number
principal quantum, and magnetic azimuth of the same, then the number
quantum spins must be opposite.
3. Principle Hund: for filling electrons in orbitals in a sub
Skin is that the electrons do not form pairs of electrons
before each filled with an electron orbital.
Example:
- Atom C with an atomic number of 6, meaning it has 6 electrons and how
Charging orbitals are:
Based on the principle Hund, the first electron from 2s trajectory will
move to track 2pz, so now there are 4 electrons
pairs. Therefore, for all orbital is full, then the atom
carbon bonded to elements that can give 4 electrons.
So that in nature there is a compound CH4 or CCl4, but there is no
CCl3 compound or CCL5
