C4 Flashcards
(44 cards)
Which number tells you which element an atom is?
The proton (atomic) number
What happen to early attempts to find connection between the chemical properties of elements and their relative atomic masses?
They were dimissed by scientific community
Briefly outline the contribution that Doberiner made to the early development of the periodic table
In 1817 Johann Dobereiner proposed his ‘ law of triads’. He realised the relative atomic mass of the mass middle element in group in a group of three elements ( that had similar properties) was close to the average of the other two elements
Outline the contributions that Newlands made to the early development of the periodic table
He arranged the known elements in order of their atomic masses. He proposed a’law of octaves’ meaning every eighth element had similar properties.This did not work for all the known elements , so was dissmied by the scientific community.
State the contributions that Mendeleev made to the development of the periodic table.
He put the known elements in order of relative atomic mass but left gaps for undiscovered elements. He also predicted what the properties of these undiscovered elements might be.
Why was Mendeleev’s table ultimately more successful than had come before?
He put the known elements in order of relative atomic mass but left gaps for undiscovered elements. He also predicted what the properties of these undiscovered elements might be.
In terms of sub-atomic particles what do the relative atomic mass and the atomic number tell us?
The atomic number gives us the number of protons and electrons in an atom of an elements. The relative atomic mass tell us the number of protons +the number of neutrons
Where is a group in the periodic table?
A vertical column of elements
Where is a period in the periodic table?
A horizontal row of elements
Approximately where can metals and non metals be found on the periodic table?
Metals on the left and in the middle, non-metals on the right
What are the group 1 elements also known as?
The alkali metals.
Describe the appearance of the group 1 metals when they have been freshly cut.
They are silver and shiny.
What happens to the group 1 metals when they are exposed to air? Why is this?
They tarnish and become dull due to reacting with moisture and oxygen in the air
Describe the reactions of lithium, sodium and potassium in cold water.
All the alkali metals react vigorously with cold water. In each reaction, hydrogen gas is given off and meal hydroxide is produced.
What is the reaction of lithium and water?
Lithium + water =lithium hydroxide + hydrogen
What is the symbol equation for sodium reacting with water?
2Na(s) + 2H2O (I) = 2NaOH(aq) + H2 (g)
Alkali metals react vigorously with chlorine. Describe the appearance and formula of the product formed.
A colourless, crystalline salt is formed with the formula MCl ie LiCl or KCl
Give an example of show that the alkali metals become more reactive as the group it descended.
In their reactions with water, the reactions become increasingly vigorous as you go down the group.
State and explain one precaution necessary when working with group 1 metals and alkalis.
Strong alkalis are corrosive , so care must be taken when they are in use for example by using goggles and gloves
Identify the states and appearances of chlorine , bromine, and iodine at room temperature and pressure.
Chlorine = green gas Bromine = reddish-brown liquid Iodine = Dark-purple
Halogens consist of diatomic molecules: what does this mean?
It means the element exist as molecules of twos
Describe the reactivity of the halogens as the group descends. Give an example to show this.
The reactivity of the halogens decreases as we move down the group. This can be shown by looking at displacement reactions. For example, When chlorine is added to sodium bromide solution , the chlorine takes the place of the bromide, Because chlorine is more reactive than bromine. This make it sodium chloride.
How can the trend in reactivity for halogens be demonstrated by displacement reactors?
The most reactive halogen displaces all the other halogens from the solution of their salts, and is itself displaced by none of the others. The least reactive halogen displaces non of the others and is itself displaced by all the others
State and explain the safety precautions necessary when working with halogens
Because the halogens are very reactive and poisonous, car must be taken when using them. Chlorine is only used in a fume cupboard. Iodine should not be handled ( it will damage skin) Gloves may be used and goggles should be worn
