CHEMISTRY

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...

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 elem...

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 particles are Incompressib...

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...

Radioactivity  is the spontaneous emission of radiation from the nucleus of an atom.                 Radioactive elements Examples of radioactive elements include: 1. Uranium (U) 2. Radium (Ra) 3. Thorium (Th) 4. Polonium (Po) 5. Actinium (Ac) etc                   Types of radiation  There are three main types of radiations emitted during radioactive decay: I. Alpha (α) rays II. Beta (β) rays III. Gamma (γ) gamma             Properties of Alpha Rays (α) 1. Alpha rays are positively charged particles made up of two protons and two neutrons (same as a helium nucleus, ⁴₂He ). 2. Each alpha particle carries a +2 charge. 3. They are heavy compared to beta particles and gamma rays. 4. They travel at a low speed (about one-tenth the speed of light). 5. They have very high ionizing power 6. They have low penetrating power. They can be stopped by a sheet ...

Energy can be defined as the capacity to do work.                        Forms of Energy The different forms of Energy are: 1. Mechanical energy  2. Chemical energy  3. Electrical energy  4. Heat energy  5. Nuclear energy  6. Light (Photon) energy  7. Sound energy  8. Magnetic energy          All matter possess energy in one form or the other. When energy changes from one form to another, the total amount of energy before and after the change are always the same. This is the law of conservation of energy.         The law of conservation of energy states that energy can neither be created nor destroyed but it can be changed from one form to another.       Energy changes in chemical reactions Energy changes occur during chemical reactions because the reactants and products possess different amounts of chemical energy. The fo...