1 Periodic Table - Notes Booklet.pdf

PERIODIC TABLE HAZARD SYMBOLS  PERIODIC TABLE Periodic table The modern periodic table is a list of elements arranged in increasing atomic number. It is arranged into horizontal periods & vertical groups. The development of the modern periodic...

PERIODIC TABLE HAZARD SYMBOLS  PERIODIC TABLE Periodic table The modern periodic table is a list of elements arranged in increasing atomic number. It is arranged into horizontal periods & vertical groups. The development of the modern periodic table was largely brought about by the following scientists: Fire ancient greeks They defined elements as basic substances from which Air Earth all other materials are made. Stated there were 4 elements: Earth, Air, Water, Fire. Water  PERIODIC TABLE Robert boyle Element cannot be split up into simpler substances by chemical means. Stated that compounds were combinations of elements. Humphrey Davy Used electrolysis to break down water into hydrogen and oxygen. Isolated potassium and sodium. Johnann Dobereiner Grouped elements three at a time into triads with similar chemical properties The atomic weight of the middle element in the triad was always half way between the other two This idea only only worked for a small number of elements. Dobereiner’s Triads  PERIODIC TABLE john newlands Arranged elements in order of increasing atomic weights. He found that the eighth element had properties similar to the first. He called these groups octaves. Only worked for the 1ˢᵗ 17 elements known at that the time. Law of Octaves was not accepted. Law of Octaves because of it’s similarity to musical octaves Li Na K Be Mg Ca B Al ? C Si ? N P As O S Se F Cl Br  PERIODIC TABLE Dmitri Mendeleev He arranged the elements in order of increasing atomic weight However he: Listed in subgroups elements such as Cu & Ag whose properties did not fit into the main group. Put Iodine & Tellurium out of order of Atomic weight. Left gaps for undiscovered elements When the elements he predicted were discovered & their actual properties matched his predictions, his table was accepted Henry Moseley He arranged the elements in terms of atomic number, not atomic weight. He used X-rays to determine the number of protons in the nucleus of an atom. This explained some of the apparent problems in Mendeleev’s table, and elements now naturally fell into their correct positions.  PERIODIC TABLE Differences in Periodic Tables Mendeleev’s Table Modern Table Elements have been discovered to fill the Gaps left for missing elements gaps Noble gases missing Noble gases included as Group 0 Only included the 63 known elements at Many new heavier elements added the time d-block elements split up and put into d-block elements arranged into a separate subgroups beside the main group block Elements in order of increasing atomic Elements mostly in order of atomic weight number Table 1.3 The difference between Mendeleev’s periodic table and the modern periodic table. alkali metals They make up the Group 1 elements & have increasing reactivity down the group. Physical Properties: Soft metals Increasing Reactivity Low densities Chemical Properties: Metallic shine when freshly cut but tarnish quickly in air. Burn readily in air. React vigorously with water & must be stored in oil. 2K + 2H₂O → 2KOH + H₂  PERIODIC TABLE alkaline earth metals They make up the Group 2 elements. They have increasing reactivity down the group. Physcial Properties: Harder than alkali metals. Chemical Properties: React less vigorously with water than alkali metals. the halogens They make up the Group 7 elements. Their reactivity decreases going down the group Physcial Properties: Low melting & boiling points, which increase down the group Usually liquids or gases at room temperature Chemical Properties: Violently react with Group 1 to form white salts: 2Na + Cl₂ → 2NaCl React with hydrogen to form acids: H₂ + Br₂ → 2HBr  PERIODIC TABLE the noble gases They make up group 0 and & are extremely unreactive. They have a full outer shell of electrons. Physcial Properties: Gases at room temperature Chemical Properties: Least reactive of all elements. Transition metals These metals are located in the centre of the periodic table. Physcial Properties: Very hard, with high melting points Good conductors of heat and electricity Chemical Properties: Form colourful compounds