Chemistry

Chemistry

ELECTROPLATING

Electroplating is a process of depositing a thin layer of a fine and superior metal (like chromium, zinc, nickel, gold etc.) over the article of a baser and cheaper metal (like iron, copper, brass), with the help of electric current. Uses Electroplating is very useful because of the following reasons:   Surface protection e.g. nickel […]

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Chemistry

ELECTROLYTES AND NON-ELECTROLYTES

However, if the compound is unable to ionise it does not conduct electricity it is called a non-electrolyte. In general, the extent to which an electrolyte can break up into ions categorises an electrolyte. This gives a measure of the degree of dissociation (a) of an electrolyte. Based on this degree the electrolytes can be

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Chemistry

SALTS

General Preparation of Salts Salts are generally ionic compounds formed by the reaction of an acid with a base. The preparation of these salts involves the treating of different metals and non-metals and their compounds with various acids, bases etc. However, some of them can be prepared by direct combination of the concerned elements or

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Chemistry

BONDING IN METALS

Bonding in metals Metal atoms have relatively few electrons in their outer shells. When they are packed together, each metal atom loses its outer electrons into a ‘sea’ of free electrons (or mobile electrons). Having lost electrons, the atoms are no longer electrically neutral.   They become positive ions because they have lost electrons but

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Chemistry

THE PHYSICAL PROPERTIES OF DIAMOND

Diamond Has a very high melting point (almost 4000°C). Very strong carbon-carbon covalent bonds have to be broken throughout the structure before melting occurs. Is very hard. This is again due to the need to break very strong covalent bonds operating in 3-dimensions. Doesn’t conduct electricity. All the electrons are held tightly between the atoms,

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Chemistry

COVALENT BONDING – SINGLE BONDS

COVALENT BONDING As well as achieving noble gas structures by transferring electrons from one atom to another as in ionic bonding, it is also possible for atoms to reach these stable structures by sharing electrons to give covalent bonds.   Depending on the number of electron pairs shared between atoms which participate in bonding, covalent

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Chemistry

STRUCTURE AND BONDING

STRUCTURE AND BONDING Ionic (Electrovalent) Bonding Noble gases like neon or argon have eight electrons in their outer shells (or two in the case of helium). These noble gas structures are thought of as being in some way a “desirable” thing for an atom to have. When other atoms react, they try to organize electrons

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Chemistry

Periods

Characteristics of periods The first period starts with hydrogen (H) and ends with helium (He). It has just two elements H (Z=1) and He (Z = 2). H has one electron in the first-shell. He has 2 electrons in the first-shell. As we have seen in the chapter on the structure of atoms, the first-shell

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Chemistry

THE NOBLE GASES – GROUP 0

THE NOBLE GASES – GROUP 0 In this group, we have Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe) and Radon (Rn). The electronic configuration will show that these atoms all have a complete outer shell of electrons and are not interested in reacting with other elements.   These elements are therefore chemically

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Chemistry

The Halogens – Group 7

THE HALOGENS – GROUP 7 The halogens are all in group 7 on the right of the periodic table. This group consists of elements like Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I), Astatine (At). The Halogens are typical non-metals and form the 7th Group in the Periodic Table ‘Halogens’ means ‘salt formers’ and the

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Chemistry

Trend In Atomic Radius

TREND IN ATOMIC RADIUS Going down Group 2: There are more filled energy levels between the nucleus and the outer electrons, therefore the outer electrons are more shielded from the attraction of the nucleus So the electrons in the outer energy levels are further from the nucleus and the atomic radius increases.   As the

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Chemistry

The Periodic Table

THE PERIODIC TABLE Dmitri Mendeleev is credited as being the Father of the modern periodic table. In 1869 he arranged the 50 or so known elements in order of atomic number, Z, putting elements with similar properties in the same vertical group, and leaving gaps for unknown elements, yet to be discovered. When the elements

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Chemistry

Isotopes

ISOTOPES It is interesting to note that atoms of a given atomic number can have different number of neutrons. Atoms of elements having the same atomic number with different mass numbers are called isotopes   Some examples are listed below: Isotopes of Hydrogen Hydrogen atom (Z=1) has no neutrons. Number of protons = 1 Number

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Chemistry

USES OF HYDROGEN GAS

USES OF HYDROGEN GAS Hydrogenation/Hardening of unsaturated vegetable oils to saturated fats/margarine. When Hydrogen is passed through unsaturated compounds in presence of Nickel catalyst and about 150oC, they become saturated. Most vegetable oil are unsaturated liquids at room temperature. They become saturated and hard through hydrogenation.   In weather forecast balloons. Hydrogen is the lightest

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