3.1 The Periodic Table Flashcards
What did Dobereiner do?
Triads, ordered by atomic weight with similar elements in the middle.
What did Newlands do?
Law of octaves, every eighth similar
What is the first ionisation energy?
The energy required to remove an electron from one atom in one mole of atoms in the gaseous state.
What factors affect first ionisation energy?
Atomic radius, nuclear charge and electron shielding
What is ductility?
the ability to be drawn out or stretched.
What is another name for group 2 elements?
Alkaline earth metals.
Reactivity trend of group 2?
Increases moving down the group.
Properties of group 2 metals?
- high melting and boiling points
- light with low densities
- form colourless (white) compounds
Reactions between group 2 elements and oxygen?
Vigorous redox reaction to produce ionic oxide.
Reactions between group 2 elements and water?
Form hydroxides with the formula M(OH)2 and hydrogen gas.
Which group two element does not react with water to form hydroxides and hydrogen?
Beryllium
Reactions between group 2 oxides and water?
form metal hydroxides
What are group 2 compounds used for?
- neutralising acid soils
- indigestion remedies
- building and construction
What is a major drawback of using group 2 carbonates as building materials?
They react readily with acids which leads to erosion due to acid rain
Why does reactivity of group 7 elements decrease down the group?
- atomic radius increases
- shielding increases
Chlorine colour in water
Pale green
Bromine colour in water
Orange
Iodine colour in water
Brown
Chlorine colour in cyclohexane?
Pale green
Bromine colour in cyclohexane?
Orange
Iodine colour in cyclohexane?
Violet
What is it called when the same element is both reduced and oxidised?
Disproportionation reaction.
Define disproportionation reaction.
The oxidation and reduction of the same element in a redox reaction.
What is formed when chlorine reacts with water?
Hydrochloric acid and chloric (I) acid
How is bleach formed?
When dilute aqueous sodium hydroxide and chlorine react at room temperature - chlorine undergoes a disproportionation reaction
How do you identify carbonate ions?
Add a dilute strong acid and collect any gas.
Fizzing and a colourless gas is produced that turns limewater cloudy.
How do you test for sulfate ions?
Add dilute HCl and barium chloride and a white precipitate of barium sulfate is produced.
-salt
Which order do you carry out tests for unknown substances?
1) carbonate test
2) sulfate test
3) halide test
How can you recognise halide ions?
They react with silver ions go form different coloured silver halide precipitates.
What colour is silver chloride?
White
What colour is silver bromide?
Cream
What colour is silver iodide?
Yellow
How do you test for halide ions?
Add aqueous solution of silver nitrate, note colour.
What do you do if the colour of the silver halide is too hard to distinguish?
Add dilute ammonia and then concentrated ammonia and the note solubility of the precipitate.
Which silver halide is soluble in dilute ammonia?
Silver chloride
Which silver halide is soluble in only concentrated ammonia?
Silver bromide
Which silver halide is insoluble?
Silver iodide.
How can you identify ammonium ions?
Add sodium hydroxide and warm. Test gas with red litmus paper. Ammonia will turn red litmus blue.
What is periodicity?
A repeating pattern (of properties shown across different periods).
Describe how van der waals forces arise.
Uneven distribution of electrons
Creates instantaneous/temporary dipole in molecule
Causes induced dipoles in neighbour molecules
Why do simple covalent compounds have low boiling point
Only induced dipoles between molecules
What is important when drawing ionisation energy graphs?
Ignore subshells
Why does Mg have a higher melting point than Na?
Magnesium ions have a greater charge
Magnesium has more outer delocalised electrons
Magnesium has greater attraction between ions and electrons OR stronger metallic bonding
Explain decreasing nuclear radius across period
Protons and nuclear charge increase
Shielding remains the same
Greater pull
Do subshells affect shielding?
No
Is a barium ion larger or smaller than a barium atom? Explain
Smaller
Less shielding
Why does Be have a higher first ionisation energy than B
In B, election being removed is at a higher energy
An s electron is lost in Be AND a p electron is lost in B
Why does the reactivity of group 2 decrease down the group?
- increasing atomic radius
- nuclear attraction decreases
- ionisation energy decreases (less energy needed to remove electrons)
Why do successive ionisation energies increase with ionisation number?
radius decreases
attraction between remaining neutrons and electrons increases
