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COMPARE THE ELEMENTS OF CHEMISTRY

It differentiates elements from each other is the "number of protons" and sheer number of an element or bonding electrons in the atomic nucleus. For example, all carbon atoms have a proton much as 6 units, while the oxygen atoms have a proton 8 units. Pada sebuah proton number of atoms is known as the atomic number (symbolized by Z) .However Thus, the atoms of the same element can have a number of different netron yang; this is known as isotopes. The atomic mass of an element (dilambangkan dengan "A") is the average atomic mass of an element in nature. Because the electron mass is very small, and the mass of the neutron is almost equal to the mass of the proton, the atomic mass is usually expressed by the number of protons and neutrons in the nucleus, the isotope that has kelimpahan terbanyak in nature. The size of the atomic mass is the atomic mass unit (smu). Some isotop bersifat radioactive, and decompose (decay) of the alpha or beta particle radiation.

chemical symbol Before chemistry became science, alchemy experts have determined both the symbols for both metals and other common compounds. They use abbreviations in diagrams or procedures; and without the concept of an atom combine to form molecules. Dengan perkembangan theory of matter, John Dalton introduces symbols of a more simple, grounded by a circle, which is used to describe molekul. Sistem currently in use was introduced by Berzelius. In the typography system, the chemical symbol used is an abbreviation of the Latin name (because at that time Latin was the language of science); for example Fe is the symbol for the element Ferrum (iron),Cu is an element simbol untuk Cuprum (copper),Hg is the symbol for the element hydrargyrum(Mercury), and chemical sebagainya. Simbol used internationally, although the names of elements translated between languages. The first letter of a chemical symbol written in capital letters, while the next letter (if any) is written in small letters.

I. Nature of Primary Elements 

A. Halogena.

Halogen Chemical Properties 

1) Halogen is highly reactive groups in accepting electrons and acts as a strong oxidizing agent in one group. Growing up, the stronger the oxidizing agent. 

2) halogen Electronegativities the Group increasingly greater upward. The most electronegative element than any other element in the periodic system is fluorine (note the data electronegativity).

 3) The radius of the halogen atom in the group getting to the top of the smaller (note data). This means getting to the top of the smaller molecular size, then the attractive force between molecules (Van der Waals forces) will become smaller. Note also the boiling point and melting point, the more up vanishingly small.Halogen element is very dangerous to the eyes and throat. Halogens have a stimulating odor and color. Although bromine is a liquid, but bromine is easy to evaporate. Likewise iodine, easy to sublimate.

4) The element of the halogen group oxidation. Sequence halogen oxidizing power can be seen from its reduction potential data:

F2 + 2 e -> 2 F; E ° = +2.87 V

Cl 2 + 2 e -> 2 Cl; E ° = +1.36 V

Br 2 + 2 e -> 2 Br; E ° = +1.07 V

I2 + 2 e -> 2 I-; E ° = +0.54 V

Based on these data, further to the above, the oxidation power (oxidizing) stronger. This data can be used to predict whether the reaction of halogen to halide compounds can take place or not. How to calculate the cell potential, if the potential price-positive cells means the reaction takes place and if the negative cell potential price means the reaction does not take place.

5) Having more than one oxidation number, except fluorine.

B. Nature Physics Halogen

II. Noble gases

Noble gas elements in the periodic system occupies a Group VIII A of the element Helium (He), Neon (Ne), Argon (Ar), krypton (Kr), Xenon (Xe) and radon (Rn). The structure of the outer electron octet noble gas (8) (except helium duplet (2)) is the most stable structure, therefore it is difficult noble gases react with other elements, so-called inert gas (slow). In 1962 Neil Bartlett succeeded in synthesizing a noble gas compound that is XePtF6. In the short time that other chemists showed that xenon can react directly with Fluor forming XeF2, XeF4, and XeF6. Since then the term inert is no longer appropriate and chemists began referring to the group of noble gases.

1. The nature of Noble Gas

- Being a noble gas

The noble gases exist as monoatomic colorless gas, is closely related to the structure of the electron octet and duplet of noble gases. While the form of gas at room temperature due to the melting point and boiling point lower noble gas.

- Melting point and boiling point

Melting point and boiling point of the noble gas increases with atomic number. This is due to the increasing dispersion forces between noble gas atoms corresponding increase in the relative atomic mass (Ar).

- solubility Noble gas

solubility in water grows from Helium (He) to Radon (Rn). At a temperature of 0 ° C in 100 ml of water was dissolved 1 ml of He, Ar 6 ml, and 50 ml of Rn.

- Elements of the noble gas contains 8 electrons in their outermost shells unless He contains two electrons.

- ionization energy is very high, noble gas elements consequently difficult to react with other elements.

- Molecules monatomic noble gases. 

C. Alkali

1. Physical Properties of Alkali

             It can be seen that as the metals, alkaline earth group has unusual properties, namely a relatively low melting point, rapatan nya relatively low, and kelunakan nya. All this alkali metal element can easily be deformed by squeezing between the thumb and forefinger (to protect the skin well). The elements in this group have the ionization energy and electronegativity lowest average. This is because the size of atoms and the relatively large distance between the outermost electron to the nucleus

III. Soil Alkali Metals

Alkali Soil Physical 

1.character
               Alkaline earth metal element (IIA) is composed of Be, Mg, Ca, Sr, Ba, and Ra. This class has properties similar to the class IA. The difference is that it has a group IIA ns2 electron configuration and is a strong reducing agent. Although tougher than class IA, class IIA but is still relatively soft, shiny silver, and has a melting point and a higher density.

               The elements of alkaline earth metal bit harder, hardness range of barium which is approximately as hard as lead, beryllium yag until hard enough to scrape most of the other metals. This class has a simple electron structures, elements of alkaline earth metals have two electrons relatively easily removed. In addition to the relatively low ionization energy, electronegativity average group was also lower due to the size of the atom and the relatively large distance between the outermost electron to the nucleus.

2. Alkali Soil Chemical Properties

D. Elements of the Third Period

Physical and chemical properties

Physical properties of elements Third Period

The elements in the third period consists of metal elements (Na, Mg, Al), metalloids (Si), non-metallic (P, S, Cl), and a rare gas (Ar). Electronegativities elements of the third period the greater the further right due to their atomic radius which is getting to the right is getting smaller. Antar atom in metal bonding strength increases (from Na to Al). This relates to the gain valence electrons. Silicon is a semiconductor / insulator because including metalloid. This element has a very large covalent bonds, as well as phosphorus, sulfur, and chlorine which is an insulator because it includes non-metals (Source: http://www.chem-is-try.org).

Chemical properties of elements Third Period

Sodium is the strongest reducing agent, while chlorine is a powerful oxidant. Although sodium, magnesium, and aluminum is a strong reducing agent, but the reactivity was reduced from Na to Al. While silicon is a very weak reducing agent, so it can only react with the oxidant-strong oxidizing agents, such as chlorine and oxygen. On the other hand other than as a reducing agent, phosphorus is also a weak oxidant which can oxidize strong reducing agent, such as active metal. While the reduction of sulfur that have a weaker than phosphorus turned out to have stronger oxidizing power than phosphorus. While chlorine can oxidize nearly all metal and nonmetal because chlorine is an oxidant-element kuat. Unsur third period, ie NaOH, Mg (OH) 2, Al (OH) 3, H2SiO3, H3PO4, H2SO4 and HClO4.

The nature of the elements hydroxide third period depends on the ionization energy. It can be seen from the type of bond. If the bonds M - OH are ionic and alkaline hydroxides because it will release OH- ions in water, low ionization energy. But if the bond M - OH covalently and no longer able to release OH- ions, then the large ionization energy. NaOH relatively strong base and easily soluble in water, Mg (OH) 2 is weaker than NaOH but still includes a strong base. But Al (OH) 3 is amphoteric, meaning that it can be acidic and alkaline. This means that when Al (OH) 3 is present in strong alkaline environment, it will be as acidic, otherwise if it is in a strong acid environment, it will act as a base. While H2SiO3 or Si (OH) 4, is a weak acid and is unstable, it is easy to break down into SiO2 and H2O. Similarly, H3PO4 or P (OH) 5, which is also a weak acid. While H2SO4 or S (OH) 6 is a strong acid, as well as HClO4 or Cl (OH) 7 which is a very strong acid.

E. Transition Elements

In the periodic system of elements, which are included in the class of transition are the elements of class B, starting from the IB - VIIB and VIII. In accordance with the charging of electrons in sub kulitnya, these elements include the d-block elements, ie elements with valence electrons located in the d subshell electron configuration. In this part of the transition elements that will be discussed are transition elements in period 4, consisting of scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), and zinc (Zn).1. Nature of Transition Metals All the elements of the transition is a metal, which is a soft, shiny, and electrically and heat. Silver is a transition element that has the highest electrical conductivity at room temperature and copper in second place. Compared with class IA and IIA, transition metal elements harder, has a melting point, boiling point, and higher density. This is because the transition elements share electrons in the skin d and s, so the bond is getting stronger.2. Oxidation Numbers Unlike class IA and IIA only has the oxidation number of +1 and +2, transition metal elements have several oxidation numbers. As vanadium has the oxidation number of +2, +3, and +4.3. Nature of Magnetism Every atom and molecule has magnetic properties, that is paramagnetic, in which atoms, molecules, or ions bit can be pulled by magnetic fields because there is an unpaired electron in the orbital and diamagnetic, in which atoms, molecules, or ions can be rejected by a magnetic field because all electrons in orbit in pairs. While in general the transition elements are paramagnetic because they have unpaired electrons in the d orbitals her. Paramagnetic properties of this would be stronger if the number of unpaired electrons in the orbital more. Metals Sc, Ti, V, Cr, and Mn is paramagnetic, while Cu and Zn is diamagnetic. For Fe, Co, and Ni are ferromagnetic, ie the same conditions as paramagnetic only in the solid state.

The nature of element periodicity, Periodic nature is the nature of that change irregularly in accordance with the increase in number of Atom, that is, from left to right in a period or from left to right in a single class.

1. The radius of the Atom

Atomic radius is the distance from the core to the outer electron shell.The larger the atomic number of the elements of a class, the more the number of kulitelektronnya, so the larger the radius of the atom.So: in one group (from top to bottom), their atomic radius increases.In one period (from left to right), atomic number increases, which means the increasing nuclear charge, while the number of electron shell remains. As a result, the core attractionto the greater outer electrons, resulting in increasingly smaller radiiatom.So: in one period (from left to right), their atomic radius smaller. 

2.Afinitas electron

Is the energy released or absorbed by neutral atoms in gas form when it receives an electron to form a negative ionMain group elements have a marked negative electron affinity, except for group IIA and VIIIA.The electron affinity owned group VIIa ..In one group (from top to bottom), the price of the smaller electron affinity.In one period (from left to right), the price of the greater electron affinity.Example: Cl (g) + e → Cl (g) (ΔH = -348kj)

3. Ionization energy

Is the minimum energy required in the form of a gas of neutral atoms to release one electron to form a +1 charged ions (cations).If these atoms release electrons to-2 then it would take a larger energy (called the second ionization energy), and so on.EI 1 <style = "font-style: italic;"> increases, so pull the nucleus and the outer electrons gets smaller. As a result, the outer electrons are easier to unload.In one period (from left to right), EI even greater because the radius of atomic nucleus less so the tensile strength of the outer electrons bigger / stronger. As a result, the outer electrons are more difficult to remove.Example: 11 Na + ionization energy → Na + + e

4. electronegativity

Is the ability of an element to attract electrons in a molecule of a compound (the sting) .using the Pauling scale of between 0.7 (electronegativity Cs) to 4 (electronegativity F).In one period (from left to right), the price of the greater electronegativity.In one group (from top to bottom), the price of the smaller electronegativity. In one class from top to bottom The smaller the electron.

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