The Periodic Table of Elements

Question 1:Name the scientists that made the following discoveries: (a) Classified elements into four groups according to their chemical properties, that is gases, non-metals, metals and metal oxides(b) Proposed the Law of Octaves(c) Constructed the triad groups consisting of three elements with similar chemical properties Answer:(a) Antoine Lavoisier(b) John Newlands(c) Johann W. Dobereiner Question 2: In … Read more

Transition Elements Transition metal is a block of metallic elements in between Groups 2 and 13 in the Periodic Table. They are much less reactive than the alkali metals. They do not react as quickly with water or oxygen as alkali metal. General Physical Characteristics All transition elements are metals. Therefore they have all the … Read more

The period is the horizontal rows of elements in the Periodic Table. The modern periodic table has 7 periods. The period number indicates the number of electron shell. Elements in the same period have the same number of electron shells. The proton number of elements increases from left to right crossing the period. The number … Read more

Chlorine + Sodium Hydroxide Cl2 + 2NaOH → NaCl + NaOCl + H2O Observation: The greenish chlorine gas dissolves quickly in sodium hydroxide, forming a colourless solution. Discussion: Chlorine gas reacts with sodium hydroxide to form a salt of sodium chloride, sodium chlorate(I) and water. Bromine + Sodium Hydroxide Br2 + 2NaOH → NaBr + NaOBr + H2O Observation: The … Read more

 Chlorine + Iron 3Cl2 + 2Fe → 2FeCl3 Observation The iron wool burns vigorously with a bright flame, forming a brown solid after the reaction. Discussion Chlorine reacts with iron to form brown iron(III) chloride. The reaction of potassium with concentrated hydrochloric acid produces chlorine gas. 2KMnO4 + 16HCl → 2KCl + 2MnCl2 + 5Cl2 + … Read more

Chlorine + Water Cl2 + 2H2O → HCl + HOCl Observation: Chlorine gas dissolves in water to form a pale yellow solution. The solution turn blue litmus paper red before it is bleached. Discussion: The solution formed is acidic and contains bleaching agent. Hypochlorous(I) acid is a strong bleaching agent. It decolourises the colour of … Read more

Chemical Properties of Halogens Group 17 elements are very reactive non-metals. The atoms all have 7 valence electrons, makes them have very similar chemical properties. During a chemical reaction, the atom gains one electron to form an ion with a charge of -1. The reactivity of group 1 decreases down the group. All group 17 … Read more

Physical Properties of Halogens All group 17 elements are non-metals. Therefore they are heat and electricity insulator. The table below shows the electron arrangement and physical properties of group 17 elements. Name Colour Melting point Boiling point Fluorine pale yellow gas -220ºC -188ºC Chlorine Yellowish green gas -102ºC -34ºC Bromine dark red liquid, brown vapour … Read more

Group 17 elements are typical non-metals and also known as halogens. The elements in this group are fluorine. chlorine, bromine, iodine and astatine. In nature, all halogens exist as diatomic molecules. They are written as F2, Cl2, Br2, I2 and As2. Most of the halogens exist in nature as halide salts. Halide is the name … Read more

Alkali Metals React with Water Group 1 metals react vigorously with water produces alkali and hydrogen gas Group 1 Metals + Water → Alkali + Hydrogen gas Common Observation Lithium, sodium or potassium floats and move around on the surface of the water and then dissolve in the water.Conclusion:Lithium, sodium and potassium are less dense than water. … Read more