2.2 - Group 2 and Group 7 Elements Flashcards
What is the trend in atomic radius as you go down group 2?
As you go down group 2, the atomic radius gets larger. This is because extra electron shells are added as you go down the group
What is the trend in first ionisation energy as you go down group 2?
First ionisation energy decreases as you go down the group. This is because each element down group 2 has an extra electron shell compared to the one above which increases the atomic radius. The extra inner electron shells shield the outer electrons from the attraction of the nucleus. The positive charge of the nucleus does increase as you go down a group (because of the extra protons) but this effect is overridden by the effect of the extra shells
What is the trend in reactivity as you go down group 2?
Reactivity increases as you go down the group as it is easier to lose electrons as the attraction between the nucleus and outer electron is weaker
What is the trend in melting point as you go down group 2?
Melting points generally decrease down group 2 as the metal ions get bigger, meaning the attraction between the delocalised electrons and the ion is weaker. Magnesium is an anomaly to this rule with it being the lowest melting point due to a change in crystal structure
What happens when group 2 metals react with water?
It gives a metal hydroxide and hydrogen
What is the trend in reactivity with water as you go down group 2?
They react more readily with water as you go down the group as the first ionisation energy gets lower
How does the solubility of group 2 metals change when you go down the group with hydroxide ions?
Solubility increases as you go down the group (magnesium is least soluble with barium being the most soluble)
How does the solubility of group 2 metals change when you go down the group with sulfate ions?
Solubility decreases as you go down the group (magnesium being the most soluble with barium being the least soluble)
What is barium sulphate used for?
As Barium Sulphate is insoluble, it is used to diagnose problems with the oesophagus, stomach or intestines
What is Magnesium used for?
Magnesium is used part of the process of extracting titanium from its ore. The main titanium ore, titanium oxide, is first converted to titanium chloride by heating it with carbon in a stream of chlorine gas. The titanium chloride is then purified by fractional distillation, before being reduced by magnesium in a furnace
What is Calcium used for?
Calcium, in the form of CaO or CaCO3 is used to remove sulphur dioxide from the combustion of fossil fuels
What is calcium hydroxide used for?
It is used in agriculture to neutralise acidic soils
What is magnesium hydroxide used for?
It is used in some indigestion tablets as an antacid (to neutralise excess stomach pH)
What is the trend of boiling points as you go down group 7?
The boiling point increases as you go down the group as the strength of the van der Waals forces increases due to the size and relative mass of molecules increasing
What is the trend in electronegativity as you go down group 7?
Electronegativity decreases down the group. Larger atoms attract electrons less than smaller ones because their outer electrons are further from the nucleus and are more shielded because they have more inner electrons
