Intro To Chemistry Ch. 1
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What are the two types of materials found on earth?
Mixtures or pure substances.
What is the atomic number?
Number of protons in a given atom.
Who first defined the element and what was the definition?
Empedocles was the first to define the element as a basic substance that all other materials are made from.
How did Robert Boyle define the element?
As a substance that cannot be broken down into simpler materials.
What are compounds?
They are combinations of particular elements.
Who was the first person to break up a compound?
Humphrey Davy
What is the process did Humphrey Davy use to break up a compound?
Electrolysis
Who discovered that the nucleus has a characteristic positive charge and what is it called?
Henry Moseley discovered the atomic number.
What are groups?
Elements that have similar properties and are arranged in vertical columns in the periodic table.
Define a period?
Horizontal row of elements.
What are the elements between groups II and III called?
D-block elements
Who suggested the ‘Law of Triads’
Johan Döbereiner
Name a triad proposed by Döbereiner?
Li, Na, K
What did John Newlands propose?
That properties of elements repeat every 8 elements but this rule only worked for the first 17, named the ‘Law of Octaves’
What did Mendeleev create?
The periodic table
What is the difference between Mendeleev’s proposal and Newland’s?
Mendeleev left gaps for undiscovered elements and placed elements that did not belong into subgroups such as Cu and Ag, he also rearranged elements based on their properties (Iodine and Tellurium).
What are the properties of Alkali Metals?
Very reactive and increase in reactivity down the group, they are soft solids that react vigorously with water.
What are Alkaline Earth metals?
They are reactive metals that increase with reactivity down the group, do not react as violently with water as Alkali metals
What are Halogens?
Very reactive non-metals that decrease in reactivity down the group, they all have low melting/boiling points and react with hydrogen to form compounds that dissolve in water
What are Noble gases?
All gases at room temp. and are the least reactive elements.