atom, molecule and ions

ATOM

Atom is a basic unit of matter, which consists of atomic nuclei and negatively charged electron cloud that surrounds it. The nucleus consists of positively charged protons, and neutrons are electrically neutral (except hydrogen-1 nucleus, which has no neutrons). The electrons in an atom bound to the nucleus by electromagnetic force. As well as a set of atoms can bind to each other, and form a molecule. Atom that contain the number of protons and electrons the same neutral, while containing a number of different protons and electrons are positive or negative and is referred to as ions. Atoms are grouped based on the number of protons and neutrons contained in the nucleus. The number of protons in an atom determines the chemical element the atom, and the number of neutrons determines the isotope of the element.
The term comes from Greek atom (ἄτομος / Atomos, α-τεμνω), which means it can not be cut or something that can not be subdivided. The concept of atoms as a component that can not be subdivided first proposed by the philosophers of India and Greece. In the 17th century and into the 18th, the chemists laid the foundations of this idea by showing that certain substances can not be subdivided further using chemical methods. During the late 19th century and early 20th century, physicists managed to find the structure and components of subatomic particles in atoms, proving that the 'atom' is not can not be subdivided. The principles of quantum mechanics used by physicists and then successfully model the atom. [1]
In everyday observation, the atom is considered a relatively very small objects that have mass also proportionally smaller. Atom can only be monitored by using special equipment such as atomic force microscopy. More than 99.9% of the mass of atoms centered on the nucleus, [note 1] with protons and neutrons are almost the same mass. Each element has at least one isotope with unstable nuclei, that can undergo radioactive decay. This can lead to transmutation, which change the number of protons and neutrons in the nucleus. [2] Electrons are bound to contain a number of atomic energy level, or orbital, which is stable and can undergo transitions between these level by absorbing or emitting photons that correspond to differences between the energy level. Electrons in atoms determines the chemical properties of an element, and influence the magnetic properties of these atoms.

Development of Atomic Theory

1. John Dalton's Atomic Theory

1. Atoms are the smallest part of matter that has not be subdivided
    2. Atom is described as a very small solid ball, an element has atoms are identical and different for different elements
    3. Atoms combine to form compounds with a ratio of integers and simple. For example, water consists of hydrogen atoms and oxygen atoms
    4. The chemical reaction is the separation or amalgamation or a rearrangement of atoms, so that atoms can not be created or destroyed.

Hypothesis Dalton atomic model as illustrated by solid balls as the shot-put. As the picture below:

weaknesses:

Daltons theory does not explain the relationship between the solution and the compound electric current conductivity.

2. J. Atomic Theory J. Thomson
atoms are neutral particles, because electrons are negatively charged, then there must be another particle-laden positifuntuk menetrallkan negative charge of the electron. From its discovery, the Thomson fix weaknesses of daltons atomic theory and atomic theory proposed, known as Thomson's Atomic Theory. Which states that:

"Atom is a solid ball is positively charged and negatively charged electrons scattered in it"

 weaknesses:

Thomson atomic model of this weakness can not explain the arrangement of positive and negative charges in the atomic sphere.

3. Rutherford Atomic Theory

experiment, known as alpha-ray scattering (λ) of thin plates of gold.

Based on the symptoms that occur, some obtained some kesipulan following:

    1. Atom is not a solid ball, because almost all the alpha particles passed
    2. If the gold plate is regarded as one lapisanatom-atom gold, then gold atoms in very small particles are positively charged.
    3. Such particles are partikelyang construct a nucleus, based on the fact that 1 in 20,000 alpha particles will be deflected. When the ratio of 1:20,000 is a comparison of the diameter, the size of the nuclei obtained about 10,000 smaller than the overall size of the atom.

Based on facts obtained from these experiments, Rutherford proposed a model of the atom, known as Rutherford Atomic Model which states that the Atomic nuclei are composed of very small and positively charged, surrounded by negatively charged electrons. Rutherford assumed that nuclei contained within the neutral particles that function binding the positive particles repel each other not to.

Rutherford atomic model can be described asfollowing : 

 

Rutherford atom

weaknesses:

Unable to explain why electrons do not fall into the nucleus of an atom.

   

4. Bohr Atomic Theory

there in 1913, Danish physicist Neils Bohr called failures to improve the Rutherford atom through experiments on the spectrum of hydrogen atoms.

explanation of the Bohr hydrogen atom involves a combination of the classical theory of Rutherford and the quantum theory of Planck, to say the four postulates, as follows:

    1. There are only a certain set of orbits allowed for single electron in a hydrogen atom. This orbit is known as a stationary state of motion (settled) electrons and is a circular path around the core.
    2. As long as the electrons are in a stationary trajectory, the electron energy remains so there is no energy in the form of radiation emitted or absorbed.
    3. Electrons can only move from one stationary trajectory into another stationary trajectory. In this transition, a certain amount of energy involved, the magnitude according to the Planck equation, ΔE = hv.
    4. Stationary trajectory is allowed to have the scale with specific properties, particularly a property called angular momentum. The amount of angular momentum is a multiple of h/2Π or nh/2Π, where n is an integer and h Planck constant.

According to Bohr's atomic model, the electrons surrounding the nucleus in certain paths called electron shells or energy levels. Lowest energy level is the electron shell which is located in, getting out of her skin and the greater the number the higher the energy level.

 

Bohr atom

weaknesses:

This atomic model can not explain the spectrum of color from many electron atoms.

5. Modern Atomic Theory

Atom model of quantum mechanics developed by Erwin Schrodinger (1926)

uncertainty principle which is "not possible to determined the position and momentum of an object closely at the same time, which can be determined is the probability of finding the electron at a certain distance from the nucleus".

Characteristic of wave mechanics model of the atom

    1.
       The movement of electrons have wave properties, so that the trajectory (orbit) is not stationary like the Bohr model, but following the completion of the square is called the orbital wave function (three-dimensional shapes darikebolehjadian greatest discovery of the electron with a particular state in an atom)
    2.
       The shape and size of the orbitals depends on the price of the three numbers kuantumnya. (Electrons that occupy the orbital quantum number is expressed as)
    3.
       The position as far as 0.529 electron from the nucleus H Armstrong by Bohr instead of something definite, but it is the biggest opportunity bolehjadi discovery of electrons.  

STRUCTURE OF ATOM

1. Elementary particles: the particles are composed of atoms forming
electrons, protons neutrons den.
1. Proton: atomic-forming particles that have a mass equal to
a sma (amu) and charge +1.
2. Neutrons: a massless particle atoms forming a sma (amu) and
Neutral.
3. Electron: atom-forming particles that have no mass and
charged -1.
2. Nucleus: a positively charged atomic nucleus, consisting of a proton den
neutrons.
3. Notation elements: z
A A with X: a sign of atoms (elements)
Z: atomic number = number of electrons
(e)
= Number of protons (p)
A: mass number = number of protons +
neutron
In neutral atoms, applies: the number of electrons = number of protons.

 4. No neutral atoms: atoms that are electrically charged due to excess or
electron deficiency when compared with neutral atoms.
Positively charged atom when an electron deficiency, called cations.
Atoms are negatively charged if the excess electron, called an anion.
example:
- Na +: cation with an electron deficiency
- Mg2-: cations with a shortage of two electrons
- Cl-: an anion with an excess of 1 electron
- O2: 2 anions with excess electrons

5. Isotopes: elements of the same atomic number but different numbers
mass.
Example: oxygen isotopes: 8
16 O; 8
17 O; 8
18 O
6. Isobars: elements of the same mass number but different numbers
atom.
Example: 27
59 CO with 28
59 Ni

7. Isoton: elements with the same number of neutrons.
Example: 6
13 C with 7
14 N

8. Iso electron: atom / ion with the same number of electrons.
Example: Na + with Mg 2 +
K + with Ar

molecule    

Molecules and Its Definition and Meaning of chemical formula


Water molecules and PartikelnyaApakah is a molecule? The molecule is a smallest indivisible part of a pure chemical compound that still retains chemical and physical properties are unique. A molecule consists of two or more atoms are bonded to one another. For example, the water molecule is a combination of two hydrogen atoms and one oxygen atom.
A molecule is written in a chemical formula. The chemical formula of a molecule that shows many types and number of atoms that make up the molecule. 

Molecular shape
1. Electron Domain Theory
● The form depends on the spatial arrangement of molecules bonding pair (PEI
and the lone pair (PEB) central atom in the molecule. can be explained
with the theory of valence shell electron pair repulsion theory or VSEPR (Valence
Shell Electron Pair Repultion)
● Molecular covalent electron pairs are both PEI and PEB.
Because the electron pairs have a similar charge, then the trade-
antarpasangan reject electrons. Repulsion (PEB - PEB)> repulsion (PEB - PEI)>
repulsion (PEI - PEI)
● The repulsive force causes the atoms are bonded
form a particular spatial structure of a molecule is thus
molecular shape is influenced by the amount of PEI or PEB held on
central atom.
● The shape of molecules is determined by the electron pair bond
Examples of CH4 molecule has 4 PEI 

 

2. Formulate Type Molecules
1) Atomic center is denoted by A
2) Domain bonding electrons is denoted by X
3) Domain of free electrons is given by E

ION
ion is an atom or a collection of electrically charged atoms. Negatively charged ions, which capture one or more electrons, called anions, because he was attracted to the anode. Positively charged ions, which lost one or more electrons, called cations, because they are attracted to the cathode. Ion formation process is called ionization. Atoms or groups of atoms are ionized tikatas marked with n + or n-, where n is the number of electrons lost or gained.
Ionic Compounds: Structure, name and nature
Ionic compound - A compound formed from the combination
ion, atom or group of atoms that pair
positive and negative electrical charge and form
because the ionic bonds (ionic bonds). ionic compounds
This is often known as salt.
Ionic bond - Pull between positive ions and negative ions
resulting from the transfer of one or more electrons from one
atom to another atom.
Ion - An atom or group of an iron atom that loses or capture
one or more electrons so it is not neutral anymore.

ION BUNCH, A STRONG CHEMICAL BONDING

Ionic bonds, sometimes referred to as bonding elektrovalen, is one type of chemical bonds of several types of chemical bonds that exist. This bond is due to the electrostatic force between the positive ions and negative ions. Ionic bond, like other chemical bonds intended that every element that binds to obtain stability as well as the noble gas elements. Ionic bond formation process is started from the ionization process, the elements that would bind first mengion
Ionic bond is a very strong bond, so that the ion is the average height of its melting point. Therefore, the high energy necessary to break the ionic bond. For example, melting point of NaCl reached 600 degrees celsius.

Covalent bonding
Covalent bond is a bond that occurs between non-metallic element with other non-metallic elements by sharing electron pairs. Sometimes the two atoms can use more than one pair of electrons. When used with two pairs or three pairs it will form a covalent bond or a triple double. The number of valence electrons are used to bind depending on the needs of each atom to achieve such a noble gas electron configuration (duplet or octet rule).
Use of shared electron pair is described by Lewis using electron dot. Lewis formula is a sign that the surrounding atoms are point, a small cross or a circle that describes the atomic valence electrons are concerned.