Elements and the Periodic Table

Question	Answer
Elements	Substances that cannot be borken down into simpler materials.
Atomic Number	Number of protons
Empedocles (Greeks)	Elements are the basic substances from which all other substances are made ; fire, earth, water, air
Robert Boyle	Elements are substances that cannot be borken down into simpler materials. Compoumds- cobinations of elements which can be formed from and broken down into these elements.
Humphry Davy	electrolysis 1. potassium, sodium 2. barium, strontium, magnesium, calcium
Henry Moseley	Nucleus has a positive charge called the ATOMIC NUMBER - led to the arrangement of elements in order of atomic number rather than mass and a more advanced definition : an element is a substance all of whose atoms have the same atomic number.
Group	Vertical
Period	Horizontal
Right of stepped line	Non-metals
Left of stepped line	Metals
Group 1	Alkalis
Group 2	Alkaline Earth Metals
Group 7	Halogens
Group 8	Noble Gases
Alkali Metals physical/chemical properties	soft, silver metals, low density reactivity increases doen the group, react with water forming hydroxide and hydrogen and with air to form oxide
What are alkali metals stored in and why?	Oil - to prevent reaction with atmospheric oxygen or with water
Alkaline earth metals physical/chemical properties	silver metals, harder then alkali metals less reactive than corresponding alkali metals, reactivity increase down the group
Halogens physical/chemical properties	Non-metals, low melting and boiling points very reactive, reactivity decreases down the group, react with hydrogen giving compounds which dissolve in water to form acidic solutions, react vigorously with sodium and other alkali metals giving white salts
Noble Gases	gases at room temperature, boiling point and density increases going down the group least reactive, inert gases
Inert Gas	Chemically unreactive
Johann Döbereiner	Triads A) Similar chemical properties B) Atomic weight of middle element half way between the other two.
John Newlands	Octaves Chemical properties repeat themselves every eighth element when arranged in order of atomic weight
Dmitri Mendeleev	He organised his table according to his 'periodic law' : Elements are arranged in order of atomic weight in such a way that elements with similar chemical properties are in the same group.
Differences between modern periodic table and Mendeleev's	n order of atomic weight rather than number. No noble gases Gaps for undiscovered elements. He put some elements in reverse order e.g. tellerium and iodine so that the elements would be in the correct order.
Image: examtime_1 (image/jpg)	Empedocles
Image: examtime_2 (image/jpg)	Robert Boyle
Image: examtime_3 (image/jpg)	Humphry Davy
Image: examtime_4 (image/jpg)	Henry Moseley
Image: examtime_9 (image/jpg)	Johann Döbereiner
Image: ecamtime_10 (image/jpg)	John Newlands
Image: examtime_11 (image/jpg)	Dmitri Mendeleev

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