CHEMISTRY

Oxygen is one of the most abundant and important elements on Earth. It is essential for respiration in humans, animals, and many other living organisms. Oxygen also supports combustion(burning). Chemical Symbol of oxygen: O Atomic Number of oxygen: 8 Mass number of oxygen: 16 Molecular Formula of oxygen: O₂                   Isotopes of oxygen  The isotopes of oxygen are: 1. Oxygen-16 (¹⁶₈O) 2. Oxygen-17 (¹⁷₈O) 3. Oxygen-18 (¹⁸₈O)                 Occurrence of Oxygen Oxygen occurs: 1. In the atmosphere as oxygen gas (about 21% of air). 2. In water (H₂O). 3. In rocks and minerals as oxides. 4. In living plants and animals.       Physical Properties of Oxygen 1. It is a colourless, odourless and tasteless gas 2. It is slightly soluble in water. 3. It is denser than air. 4. It exists as a diatomic molecule (O₂).       Chemical Properties of Oxygen 1. It suppor...

                        HYDROGEN   Hydrogen is a non-metallic element with the chemical symbol H and atomic number 1. It is the lightest and most abundant element in the universe.             Occurrence of Hydrogen Hydrogen occurs: I. In water (H₂O). II. In acids e.g. hydrochloric acid (HCl) and sulphuric acid (H₂SO₄). III. In hydrocarbons such as petroleum and natural gas. IV. In living organisms. V. In the Sun and other stars, where it is the main fuel for energy production. Physical Properties of Hydrogen 1. It is a colourless, odourless and tasteless gas 2. It is the lightest known gas. 3. It is less dense than air. 4. It is slightly soluble in water. 5. It is highly flammable. 6. It exists as diatomic molecules (H₂)                   Isotopes of hydrogen Isotopes are atoms of the same element that have the same atomic number but d...

                              pH pH  stands for the potential of hydrogen. It is a measure of the degree of acidity or alkalinity (basicity) of a solution. It is measured by an instrument called pH meter.                           pH SCALE  The pH scale ranges from 0 to 14; the lower and upper limits respectively. Note : 1. Substances with pH < 7 is  Acidic e.g.battery acid, vinegar, gastric juice etc 2. Substances with pH = 7 is Neutral e.g. Pure water, table salt etc 3. Substances with pH > 7 is Alkaline (Basic) e.g. Bile, sea water, soap solution, NaOH etc                 Importance of pH 1. pH helps to determine whether a substance is acidic or alkaline. 2. It is used in agriculture to test soil before planting crops. 3. Used in medicine to monitor body fluids. 4. H...

                                  ACIDS An acid is a substance that produces hydrogen ions (H⁺) when dissolved in water.                         Types of acids The two types of acids are: I. Organic acids II. Inorganic acids Organic acids occur naturally in plants and animals. Inorganic acids are called mineral acids, since they are produced from mineral ores. They are man- made. Examples of inorganic acids are: 1. Hydrochloric acid (HCl) 2. Trioxonitrate(V) acid (HNO₃) 3. Sulphuric acid (H₂SO₄) etc                   Properties of Acids 1.  Acids have sour taste. 2.  Acids turn blue litmus paper red. 3. Acids react with metals to produce hydrogen gas. 4. They conduct electricity in solution. 5. They have pH values less than 7.           ...

                          Radicals   A radical is a group of atoms that acts as a single unit and carries either a positive or negative charge during a chemical reaction. Radicals behave as units and take part in the formation of chemical compounds. For example: SO₄²⁻ — Sulphate radical NO₃⁻ — Nitrate radical OH⁻ — Hydroxide radical NH₄⁺ — Ammonium radical               Types of Radicals The two types of radicals are: I. Positive radicals II. Negative radicals                   Positive Radicals These are radicals that carry a positive charge . Examples:             Negative Radicals These are radicals that carry a negative charge. Examples: Characteristics of Radicals A radical consists of two or more atoms in most common cases. The atoms in ...

Valency is the combining power of an element. It determines how an element combines with other elements to form compounds. CLASSIFICATION OF ELEMENTS BASED ON VALENCY Elements may have different valencies, as I. Monovalent elements  II. Divalent elements III. Trivalent elements IV. Tetravalent elements V. Pentavalent elements I. Monovalent Elements They are elements with a valency of 1. Examples: Potassium (K), Sodium (Na), Hydrogen (H), Fluorine (F), and Chlorine (Cl). II. Divalent Elements They are elements with a valency of 2. Examples: Calcium (Ca), Barium (Ba), Magnesium (Mg), Oxygen (O), and Zinc (Zn). III. Trivalent Elements They are elements with a valency of 3. Examples: Aluminium (Al), Iron (Fe³⁺), Boron (B), and Nitrogen (N). IV. Tetravalent Elements They are elements with a valency of 4. Examples: Carbon (C), Silicon (Si), and Lead (Pb⁴⁺). V. Pentavalent Elements They are elements with a valency of 5. Examples: Phosphorus (P), Arsenic (As), and Antim...

                                  SO₄  SO₄ is called Sulphate or Tetraoxosulphate(VI). Sulphate compounds contain the sulphate ion (SO₄²⁻). It has a valency of 2. Write the chemical formula of the following compounds: 1. Sodium sulphate (Valency: Na=1, SO₄=2) 2. Potassium sulphate (Valency: K=1, SO₄=2) 3. Calcium sulphate (Valency: Ca=1, SO₄=2) 5. Copper(II) sulphate (Valency: Cu=2, SO₄=2) 6. Magnesium sulphate (Valency: Mg=2, SO₄=2) 7. Zinc sulphate (Valency: Zn=2, SO₄=2) 8. Iron(II) sulphate (Valency: Fe=2, SO₄=2) 10. Ammonium sulphate (Valency: NH₄=1, SO₄=2) 11. Barium sulphate (Valency: Ba=1, SO₄=2) 12. Aluminium sulphate (Valency: Al=3, SO₄=2)                                     NO₃ NO₃ is called Nitrate or Trioxonitrate(V). Nitrate compounds contain the nitrate ion (NO₃⁻). It has a valency of 1....

CO₃ is called Carbonate or Trioxocarbonate(IV). Carbonate compounds contain the carbonate ion (CO₃²⁻). It has a valency of 2. Write the chemical formula of the following compounds. 1. Calcium carbonate  (Valency: Ca =2, CO₃=2) 2. Sodium trioxocarbonate(IV).    (Valency: Na=1, CO₃ =2) 3. Potassium carbonate  (Valency: K=1, CO₃ =2) 4. Magnesium carbonate  (Valency: Mg=1, CO₃=2) 5. Zinc carbonate  (Valency: Zn=2, CO₃=2) 6. Copper(I) carbonate  (Valency: Cu=1, CO₃ =2) 7. Iron(II) carbonate  (Valency: Fe=2, CO₃=2) 8. Lead(II) carbonate  (Valency: Pb=2, CO₃=2) 9. Barium carbonate  (Valency: Ba=2, CO₃ =2) 10. Lithium carbonate  (Valency: Li=1, CO₃=2) 11. Ammonium carbonate (Valency: (NH₄=1, CO₃=2)                      Assignment  Write the chemical formula of the following compounds 1. Copper(II) trioxocarbonate(IV).  (Valency: Cu=2, CO₃ =2) 2....

The Kinetic Theory of Matter states that all matter is made up of small particles that are in constant motion. The particles possess kinetic energy. The arrangement of these particles determine the physical state of the matter. It also explains the behavior of matter based on the motion of its tiny particles (atoms or molecules).       Properties of the states of matter The three states of matter are: 1. Solid state 2. Liquid State 3. Gaseous state                       Solid State 1. They have definite shape and volume 2. They have strong intermolecular forces 3. Their particles are closely packed and orderly  4. Their particles are Incompressible 5. They have high density 6. Particles vibrate about fixed positions Examples: Ice, iron, wood                       Liquid State 1. They have no definite shape (they take the shape of their con...

Chemical bond Chemical bonding is the formation of a chemical bond between two or more atoms to hold them together as a stable molecule resulting in a chemical compound. Chemical bond  is the force of attraction that holds atoms or ions together in a molecule or compound.       When atoms bond, they form molecules or compounds with lower energy and greater stability.           Types of Chemical Bonding  1. Electrovalent (Ionic) Bonding  2. Covalent Bonding 3. Metallic bonding          Electrovalent (Ionic) Bonding This is the type of bonding formed when one or more electrons are transferred from a metal atom to a non-metal atom.        The metal becomes a positive ion (cation), while the non-metal becomes a negative ion (anion). The electrostatic attraction between the oppositely charged ions forms the bond. e.g. NaCl, MgO etc Example : Formation of sodium chloride (NaCl) ...

React and balance the following chemical equations 1. FeCl₃(s) + NaOH → 2. FeSO₄ + NaOH → 3. Zn + HCl → 4. Mg + HCl → 5. Ca(OH)₂ + HNO₃ → 6. FeCl₂ + NaOH → 7. Al(s) + O₂(g) → Balance the following chemical equations 

Tin is a metal with the symbol Sn (from Latin Stannum). It has valencies of +2 and +4 It is found in the earth’s crust mainly as cassiterite (SnO₂). Tin is one of the oldest metal used by man.               Physical Properties of Tin 1. Tin is a silvery-white and shiny metal. 2. It is soft and can be bent easily. 3. It can be beaten into thin sheets (malleable). 4. It has a low melting point (232°C). 5. It does not rust easily (resists corrosion).             Chemical Properties of Tin 1. It can react with oxygen to form tin oxide (SnO₂). SnO₂ + 2C → Sn + 2CO 2. It can reacts slowly with acids to give tin salts and hydrogen gas. SnO₂ + 2C → Sn + 2CO 3. Tin oxide is amphoteric (reacts with acids and bases).             Extraction of Tin Tin is obtained from cassiterite (SnO₂). The ore is heated with carbon to get tin: SnO₂ + 2C → Sn + 2CO             ...

Carbon is a non-metallic element. The symbol of carbon is  C and has atomic number 6. (₆C) Carbon is found in all living things and forms a large number of compounds known as organic compounds. Occurrence of Carbon in Nature Carbon occurs in both free and combined states. Occurrence of carbon in free state e.g. I. Diamond II. Graphite III. Coal Occurrence of carbon in combined state e.g. I. Carbon dioxide (CO₂) II. Methane (CH₄) III. Calcium carbonate (CaCO₃) It also occurs in all living organisms as part of organic matter.                       Allotropes of Carbon  Allotrope of carbon  is the different physical forms in which carbon can exists.      The ability of carbon to exist in different physical forms is called Allotropy . The main allotropes of carbon are: (a) Diamond (b) Graphite (c) Amorphous carbon                      ...

                  The Periodic Table  The periodic table is a table which shows the arrangement of all the known elements in order of their increasing atomic number.        It shows elements with similar properties placed in the same vertical columns (groups). The table has horizontal rows called periods and vertical columns called groups . There are 7 periods and 8 groups in the periodic table. Group 1 (Alkali metals) Examples : Lithium (Li), Sodium (Na), Potassium (K) Group 2 (Alkaline earth metals) Examples: Magnesium (Mg), Calcium (Ca) Group 7 (Halogens) Examples: Fluorine (F), Chlorine (Cl) Group 0 (Noble, Inert or Rare gases) Examples: Helium (He), Neon (Ne), Argon (Ar)       Importance of the Periodic Table 1. It helps to classify elements easily. 2. It shows the relationships between elements. 3. It helps scientists predict the behavior of ele...

The particulate nature of matter means that all matter is made up of tiny particles (atoms or molecules) which are too small to be seen with the naked eye. These particles are constantly moving and have spaces between them. Assumptions of the Kinetic Theory of Matter 1. All matter is made up of tiny particles. 2. The particles are in constant motion. 3. There are spaces between the particles. 4. The particles attract one another with forces of attraction. 5. The higher the temperature, the faster the particles move. States of Matter and Their Particle Arrangement The states of matter are: 1. Solid state 2. Liquid State 3. Gaseous state                              Solid State     Properties of Solid State of matter: 1. They have definite shape and volume 2. They have strong intermolecular forces 3. Their particles are closely packed and orderli 4. Their partic...

Non-metals are elements that ionize by electron gain. They are usually poor conductors of heat and electricity, brittle, and often exist as gases, liquids, or dull solids at room temperature. Examples of Non-Metals Some common non-metals include: I. Hydrogen (H) II. Oxygen (O) III. Nitrogen (N) IV. Carbon (C) V. Sulphur (S) VI. Phosphorus (P) VII. Chlorine (Cl) VIII. Fluorine (F) IX. Iodine (I) X. Bromine (Br) etc       Physical Properties of Non-Metals 1. Non-metals are brittle when solid (i.e. they break easily). 2. They are poor conductors of heat and electricity (except graphite). 3. They usually have low melting and boiling points. 4. Many are gases at room temperature (e.g., oxygen, nitrogen). 5. Solid non-metals are dull in appearance (not shiny). 6. They have low density (i.e. light in weight). 7. They are non-sonorous (do not produce ringing sound when hit).   Chemical Properties of Non-Metals 1. Non-metals gain electrons to form...