Chemistry 3 Flashcards
Why is the periodic table called this?
Similar properties occur at regular intervals.
What was the first scientist (that we learn about) that came up with a version of the periodic table?
How did he arrange them?
John Newsland - 1864
Ordered the elements in order of its atomic weights.
What is the second scientist (that we learn about) that came up with a close version of the periodic table?
How did he arrange them?
Mendeleev - early 1900
When organising the elements into the table he left gaps for the elements they hadn’t discovered yet.
When were neutrons, protons and electrons discovered?
How is the modern periodic table organised?
Early 20th Century.
Arranged in order of atomic number. Then all elements were placed into appropriate groups.
What are the elements in group one known as?
How dense are these metals?
Alkali metals
Low density - the first three are less dense than water
What does group one metals react with to create ionic compounds?
Non metals - the metal ion carries a charge of +1.
The compounds are white solids that dissolve in water to form colourless solutions
What happens if you react water and a group one metal?
Hydrogen is released.
A metal hydroxide is formed. These dissolve in water to give an alkaline solution.
In group one what is the trends for the;
reactivity?
melting / boiling point?
The further down the group an element is the more reactive it becomes.
The further down the group an element is the lower the melting / boiling point is.
What are transition metals like, in comparison to group one metals?
[4 points]
Higher melting points (except mercury)
Higher densities
Stronger and harder
Much less reactive and so do not react as vigorously with water or oxygen.
Transition metals are…
[3 points]
Some have ions with different charges
For example Fe^2+ - Fe^3+
Form coloured compounds
Useful as catalysts
What are elements in group seven known as?
What happens when they react with a metal?
Halogens
Form a ionic compound in which the halide ion carries a charge of -1.
In group seven, what are the trends for;
reactivity?
boiling / melting point?
The further down the group an element is the less reactive it is.
The further down the group an element is the higher its boiling / melting point is.
What happen when there are more than two different halogens?
Example?
A more reactive halogen can displace a less reactive halogen from an aqueous solution of its salt.
Cl2 + 2KBr ==> Br2 + 2KCl
What is hard water?
What is soft water?
Water that contains dissolved compounds like magnesium or calcium. The compounds are dissolved when they come into contact with the rock.
book
Soft water + soap =
Hard water + soap =
Lather
Scum
What are the two types of hard water?
Permanent hard water: remains hard when boiled
Temporary hard water: softened by boiling
What does temporary hard water contain?
Hydrogencarbonate ions - they decompose on heating to produce carbonate ions which react with calcium and magnesium ions to form precipitates.
What are some of the negatives using hard water + temporary hard water?
More soap is needed for a lather so it increases cost.
When temporary hard water is heated it can produce scale that reduces efficiency of heating systems and kettles.
What are the benefits of hard water?
Calcium ions are good for the development and maintenance of bones and teeth; can help reduce the risk of heart disease.
In general how can hard water be made soft?
By removing magnesium and calcium ions.
What are the two ways to make hard water sort?
Adding sodium carbonate. This reacts with the calcium and magnesium ions to form a precipitate of calcium carbonate and magnesium carbonate.
Using water softeners such as ion exchange columns containing hydrogen ions or sodium ions. This can replace the calcium and magnesium ions when hard water passes through the column.
What is the correct drinking water quality for humans?
Sufficiently low levels of dissolved salts and microbes.