Ch.1-Elements And The Periodic Table Flashcards
What is a compound?
A compounds is a substance that is made of 2 or more different elements chemically combined.
What is an element?
Elements cannot be broken down chemically into simpler substances. Elements are designated a symbol and a unique atomic number.
What was the ancient Greeks’ definition of elements?
Empedocles defined elements as the basic substances from which all other materials are made. (Earth, fire, water and air)
How did Boyle define elements?
Boyle defined an element as a substance that cannot be broken down into simpler materials.
What contribution did Humphrey Davy make?
Davy developed electrochemical techniques for breaking down compounds into elements. He isolated barium, strontium, calcium and magnesium.
How did Johann Döbereiner contribute to the periodic table?
Döbereiner suggested that elements should fit together in groups of 3 called triads. The elements in a triad would have similar chemical properties, and the atomic weight of the middle element would be midway between the other 2.
How did John Newlands contribute to the periodic table?
Newland’ law of octaves arranged the elements in order of atomic weight and found that properties seemed to repeat themselves every 8th element.
What contribution did Dmitri Mendeleev make to the periodic table?
Mendeleev listed separately in subgroups elements such as copper and silver whose properties did not fit in with those of the main groups. He also left gaps in the table in order to make elements fit into proper groups, these gaps predicted the discovery of gallium, scandium and germanium.
What are the group I elements? List their physical properties.
The group I elements are called alkali metals. They are all very reactive metals, increasing in reactivity down the group.
When freshly cut, alkali metals have a metallic shine. Alkali metals are soft (can be cut with a knife) and they have low densities (lithium, sodium and potassium float in water).
List the chemical properties of group I elements.
When freshly cut, alkali metals have a metallic shine. Metal oxide is formed when alkali metals burn in air.
They react vigorously with water, forming a basic solution and water.
Alkali metals are stored in oil to prevent reactions with water and atmospheric oxygen.
What is the chemical reaction of potassium with water?
2K + 2H20 = 2KOH +H2
What are the group II elements?
The alkaline earth elements are in group II. They are all reactive elements, with reactivity increasing down the group.
What are the physical and chemical properties of group II elements?
Alkaline earth metals are metals which are harder than the alkali metals.
They are less reactive than the corresponding alkali metals.
What are the group VII elements?
The group VII elements are halogens. They are very reactive non-metals, decreasing in reactivity down the group.
What are the physical and chemical properties of the group VII?
The halogens have low melting and boiling points. The halogens react with hydrogen to form compounds which dissolve in water to form acidic solutions.
