User talk:Khalifa.aun

Periodic Table
 2) Layout of the periodic table  The periodic table has a lot of different not only in groups and periods, but also also has different shapes and orders it could be in. The periodic table is made by Dmitry Mendeleev in 1869, but before him people put orders of the periodic table into mass not by the amount of protons or electrons there is in an element. The periodic table is separated into three categories, metals, non-metals and semi-metals. Metals are the most common category of all the categories with a total of eighty five metals on the periodic table. There are only seven semi-metals which means it is the least common category on the periodic table. There are nineteen non-metals on the periodic table and that means that it’s in the middle, not the lowest or the highest of categories. Specific regions of the periodic table can be referred to as blocks. There are three blocks S, F, D and P. “S” is the first block of the four blocks and it is located on the left. It takes up the first two groups of the periodic table and also helium which is the second element on the periodic table. The “F” block has no groups and rests on the bottom of the periodic table. The “D” block is the middle block and contains ten groups on the periodic table and contains all of the transition metals. The p-block comprises the last six groups which are groups 13 to 18 and contains, among other elements, all of the metalloids.

 3) ELEMENTS, COMPOUNDS AND MIXTURES 

What is an element?

An element is the simplest form of matter in that it cannot be further broken down using any chemical means. Yes, elements are made up of smaller particles, but you can't take an atom of an element and perform any chemical reaction that will break it apart or join its sub units to make a bigger atom of that element.

What are compounds?

A compound is a substance formed when two or more chemical elements are chemically bonded together.The elements in any compound are always present in fixed ratios.

What are mixture? In chemistry, a mixture is a material system made up of two or more different substances which are mixed but are not combined chemically. A mixture refers to the physical combination of two or more substances on which the identities are retained and are mixed in the form of solutions, suspensions, and colloids.\

 Case study: Arsenic  Arsenic is chemical element. Its symbol is 'As' it has 33 electrons, 33 protons, its atomic number is 33, the atomic mass is 75 and its number of neutrons is 42. Arsenic is usually in conjunction with metals and sulfur, also as a pure elemental crystal. Arsenic was used to much more common in the community than it is nowadays. It was used as a pigment in the nineteenth century for green wallpaper contained copper arsenite, because there weren’t any other good green pigments to make the wallpaper. And when the rooms were damp, Victorians didn't like opening the windows in their rooms, then mould would grow on the wall. And because arsenic is poisonous to most life forms the mould would convert the arsenic into a volatile compound, trimethylene, and the trimethylene went into the air and several people were killed by the arsenic coming from their wallpaper.Arsenic is also used in the electronics industry for getting electronic properties for making transistors. And also it is still sometimes used for medication for feeding to livestock. It is only quite recent that the use of arsenic has been banned as an additive to chicken feed in the United States.

 Case study: Silver  Silver is a chemical element with symbol Ag. Atomic number 47. A soft, white, lustrous transition metal, it possesses the highest electrical conductivity of any element, the highest thermal conductivity of any metal and is the most reflective metal on the planet. The metal occurs naturally in its pure, free form (native silver), as an alloy with gold and other metals. Most silver is produced as a byproduct of copper, gold, lead, and zinc refining. While silver has long been valued as a precious metal it is also used in currency coins, solar panels, water filtration, jewelry and ornaments, high-value tableware and utensils, and as an investment in the forms of coins and bullion.(gold heated extremely). Silver is used industrially in electrical contacts and conductors, in specialized mirrors, window coatings and in catalysis of chemical reactions. Its compounds are used in photographic film and X-rays. Dilute silver nitrate solutions and other silver compounds are used as disinfectants and micro biocides (disinfection) added to bandages and wound-dressings, and other medical instruments.

 Importance of the America  The modern periodic table has changed since Dmitri Mendeleev’s original table. Yet both tables (The modern table and Mendeleev’s table) are important for a same reason: The periodic table organizes elements for similar properties so you can probably tell the characteristics of an element by looking at its position in the periodic table.

The table is used by many modern students, teachers and scientists. It helps them predict the chemical reactions of an element. Elements in the same column (Groups) have the similar properties. For example: The elements in the first column are called The Alkali Metals, those elements react vigorously with water. They carry a 1+ charge in reactions.

The elements in the same row (Periods) share high electron energy levels. The periodic table is the most important chemistry reference there is, it has gone through many different revisions over the years by scientists which made them gain more knowledge about the atoms and the atomic structure of the elements.