Group 1
What name is given to group 1 elements?
Alkali metals
What is the oxidation state of oxygen in barium peroxide?
Oxidation state: −1
What is produced when lithium reacts with water?
lithium hydroxide and hydrogen
State the color of the flame for the following Metal Ions
1) Sodium
2) Strontium
3) Magnesium
1) Yellow
2) Crimson Red
3) No Color
The electronic configuration of lithium can be shortened to [He]2s1. Using this style, give the electron configurations of:
a) sodium
b) potassium.
a) [Ne]2s1
b) [Ar]2s1
Write balanced equations for the reactions of strontium with oxygen
2Sr(s) + O2(g) → 2SrO(s)
Write balanced equations and use oxidation numbers to show that sodium acts as a reducing agent when it reacts with:
a) water
b) chlorine.
a) 2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)
b) 2Na(s) + Cl2(g) → 2NaCl(s)
Z is a white crystalline solid which colors a flame lilac. Identify the metal ion.
Potassium ion/K+
The first ionisation energies of the alkali metals get smaller down the group. Why is this?
The charge on the nucleus increases and the number of inner full shells also increases. The shielding effect of the inner electrons means that the effective nuclear charge attracting the outer electron is 1+. Down the group the outer electrons get further and further away from the same effective nuclear charge and so they are held less strongly and the ionisation energies decrease.
Radium is a highly radioactive element which is below barium in the Periodic Table. Use your knowledge of the chemistry of the elements Mg to Ba in Group 2 to predict properties of radium and its compounds. Include in your predictions a description of the following changes, equations for any chemical changes and the appearance of the products the reaction of radium with oxygen
Expect radium to burn brightly in oxygen forming a white oxide (or peroxide) RaO/RaO2
2Ra(s) + O2(g) → 2RaO(s)
or
Ra(s) + O2(g) → RaO2(s)
State the formula of the compound formed when calcium reacts with bromine.
CaBr2
On heating to just above its melting temperature, KClO3 reacts to form KClO4 and KCl. Write a balanced equation for the reaction.
4KClO3(s) → 3KClO4(s) + KCl(s)
Write balanced equation for second Ionisation energy of potassium.
K+(g) → K2+(g) + e–
Assess whether magnesium fluoride is likely to be more or less soluble than barium fluoride.
Fluorine is an element in the second period. Its atoms and ions are relatively small. In line with the generalisation this means that solubility is expected to increase down the group from magnesium fluoride to barium fluoride.
Y is a white, crystalline solid which colours a flame green. Adding dilute nitric acid followed by silver nitrate solution to a solution of Y produces a white precipitate.
Y is barium chloride. Green flame suggests barium. The white precipitate with silver nitrate indicates chloride ions.
Why concentrated hydrochloric acid is used in flame test?
It is used to convert the metal compound being tested into a chloride, because chlorides are usually volatile and so, more likely to produce a better flame colour.
Justify that the reactivity of group 1 elements increases as we go down the group.
The metallic character of the element increases down the group due to the increase in the shielding as compared to the nuclear charge.
For Group 2 compounds with small anions solubility in water increases down the group; for compounds with large anions solubility decreases down the group.’
Discuss, with the help of examples, whether or not this generalisation can be justified.
Points to make in an answer:
• Solubility of hydroxides increases down the group.
• Solubility of nitrates decreases down the group.
• Solubility of carbonates decreases down the group.
• The polyatomic nitrate and carbonate ions are relatively large …
• compared to the hydroxide ion, which consists of two relatively small atoms.
• On the basis of these examples the generalisation is true
X is a white solid which colours a flame bright yellow. No precipitate forms on mixing a solution of X with sodium hydroxide solution. On heating, X gives off a colourless gas that relights a glowing splint.
X is sodium nitrate. Yellow flame indicates sodium. Sodium hydroxide is soluble. The gas is oxygen. This could be from a nitrate decomposing to the nitrite.
Z is a white crystalline solid which colours a flame lilac. Z is soluble in water – the solution does not change the colour of indicators.
Mixing the solution of a solid Y with a solution of silver nitrate produces a cream precipitate that is insoluble in dilute aqueous ammonia but soluble in concentrated aqueous ammonia. A solution of Z turns orange on adding aqueous chlorine.
Z is potassium bromide. Mauve flame suggests potassium. Potassium and bromide ions do not affect the pH of solutions. The cream precipitate with silver nitrate indicates bromide ions. Silver bromide dissolves in concentrated ammonia. Chlorine oxidises colourless bromide ions to orange bromine.