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S-Block Flashcards

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1
Q

What are the general characteristics of alkali metals?

A

Alkali metals are soft, light metals that are highly reactive and form hydroxides with water, which are strongly alkaline in nature.

Alkali metals include lithium, sodium, potassium, rubidium, caesium, and francium.

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2
Q

What is the electronic configuration of alkali metals?

A

[noble gas] ns1

This configuration indicates that alkali metals have one valence electron outside the noble gas core.

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3
Q

List the elements of Group 1 in the Periodic Table.

A
  • Lithium
  • Sodium
  • Potassium
  • Rubidium
  • Caesium
  • Francium

These elements are collectively known as alkali metals.

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4
Q

What distinguishes the first element of alkali metals from the others?

A

Lithium exhibits some properties that are different from the other alkali metals.

This is due to its unique atomic structure and behavior.

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5
Q

What is the general electronic configuration of alkaline earth metals?

A

[noble gas] ns2

This indicates that alkaline earth metals have two valence electrons outside the noble gas core.

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6
Q

Which alkaline earth metals are abundant in the Earth’s crust?

A
  • Calcium
  • Magnesium

Strontium and barium have lower abundances; beryllium is rare, and radium is the rarest.

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7
Q

What is the diagonal relationship in the periodic table?

A

It refers to the similarities in properties between the first element of a group and the second element of the following group, such as lithium with magnesium and beryllium with aluminium.

This is due to similarities in ionic sizes and charge/radius ratios.

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8
Q

What is the trend in atomic and ionic radii of alkali metals?

A

Atomic and ionic radii increase down the group from lithium to cesium.

Monovalent ions (M+) are smaller than their parent atoms.

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9
Q

How does ionization enthalpy change among alkali metals?

A

Ionization enthalpy decreases down the group from lithium to cesium.

This is due to the increasing atomic size outweighing the increasing nuclear charge.

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10
Q

What is the trend in hydration enthalpy for alkali metal ions?

A

Hydration enthalpy decreases with increasing ionic sizes: Li+ > Na+ > K+ > Rb+ > Cs+

Lithium ions have the maximum degree of hydration.

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11
Q

What are the physical properties of alkali metals?

A
  • Silvery white
  • Soft
  • Light
  • Low density
  • Low melting and boiling points

These properties change with increasing atomic number.

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12
Q

What colors do alkali metals impart to a flame during a flame test?

A
  • Lithium: Crimson
  • Sodium: Yellow
  • Potassium: Violet
  • Rubidium: Red
  • Caesium: Blue

This is due to the excitation of outermost electrons and their return to ground state.

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13
Q

How do alkali metals react with water?

A

They react with water to form hydroxides and dihydrogen: 2M + 2H2O → 2M+ + 2OH− + H2

The reactivity varies, with lithium being less vigorous than sodium.

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14
Q

What happens when alkali metals react with oxygen?

A

They form oxides, peroxides, or superoxides depending on the metal: e.g., 4 Li + O2 → 2 Li2O (oxide).

Lithium reacts with nitrogen to form lithium nitride (Li3N).

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15
Q

What is the reducing nature of alkali metals?

A

Alkali metals are strong reducing agents, with lithium being the most powerful.

This is measured by standard electrode potential.

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16
Q

What is the role of potassium in biological systems?

A

Potassium plays a vital role in maintaining ion balance and nerve impulse conduction.

It is found in large proportions in biological fluids.

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17
Q

What are the common compounds of alkali metals generally characterized by?

A

They are generally ionic in nature.

This includes their oxides and hydroxides.

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18
Q

What oxides do alkali metals form upon combustion?

A
  • Lithium: Li2O
  • Sodium: Na2O2
  • Potassium, Rubidium, Caesium: MO2 (superoxides)

The stability of these compounds increases with the size of the metal ion.

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19
Q

What is a unique application of lithium?

A

Lithium is used to make useful alloys and electrochemical cells.

It is also used in thermonuclear reactions.

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20
Q

Fill in the blank: The electronic configuration of Sodium is _______.

A

[Ne] 3s1

This indicates the arrangement of electrons in sodium.

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21
Q

True or False: Alkali metals are typically found in their free state in nature.

A

False

They are highly reactive and are never found in a free state.

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22
Q

What are the products formed when alkali metal oxides react with water?

A

M2O + H2O → 2M+ + 2OH–
M2O2 + 2H2O → 2M+ + 2OH– + H2O2
2MO2 + 2H2O → 2M+ + 2OH– + H2O2 + O2

These reactions show the hydrolysis of different oxides to produce hydroxides and other products.

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23
Q

What is the color of pure oxides and peroxides compared to superoxides?

A

Oxides and peroxides are colorless, while superoxides are yellow or orange

Superoxides also exhibit paramagnetism due to unpaired electrons.

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24
Q

Why is KO2 paramagnetic?

A

Because of one unpaired electron in π*2p molecular orbital

The presence of unpaired electrons contributes to the paramagnetic property.

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25
What are the characteristics of alkali metal hydroxides?
They are white crystalline solids, strongest bases, and dissolve freely in water with evolution of heat ## Footnote Their strong basicity is due to intense hydration.
26
What are alkali metal halides and their properties?
High melting, colorless crystalline solids, soluble in water ## Footnote They can be prepared from oxides, hydroxides, or carbonates with hydrohalic acids.
27
What is the trend in enthalpy of formation for alkali metal halides as we go down the group?
Δf H values for fluorides become less negative; for chlorides, bromides, and iodides, it becomes more negative down the group ## Footnote This indicates changes in stability and bonding characteristics.
28
Fill in the blank: The melting and boiling points of alkali metal halides follow the trend: _______.
fluoride > chloride > bromide > iodide ## Footnote This trend reflects changes in ionic size and lattice energy.
29
What defines oxo-acids?
Acidic proton on a hydroxyl group with an oxo group attached to the same atom ## Footnote Examples include carbonic acid and sulfuric acid.
30
What is the stability trend of carbonates and hydrogencarbonates down the alkali metal group?
Stability increases as electropositive character increases ## Footnote Lithium carbonate is less stable due to its small size.
31
What causes the anomalous properties of lithium compared to other alkali metals?
Exceptionally small size and high polarising power ## Footnote These factors lead to increased covalent character in lithium compounds.
32
What are the points of difference between lithium and other alkali metals?
Lithium is harder, has higher m.p. and b.p., least reactive, forms different oxides, and behaves differently with hydrates ## Footnote For example, LiCl crystallizes as a hydrate while others do not.
33
What similarities exist between lithium and magnesium?
Both are harder, lighter, react slowly with water, and have similar ionic sizes ## Footnote Both elements also form nitrides and have similar solubility properties.
34
What is sodium carbonate commonly known as?
Washing soda ## Footnote Its formula is Na2CO3·10H2O.
35
How is sodium hydroxide produced?
By electrolysis of sodium chloride in a Castner-Kellner cell ## Footnote Sodium metal reacts with water to produce sodium hydroxide and hydrogen gas.
36
What is the role of sodium hydrogencarbonate in cooking?
It decomposes on heating to generate carbon dioxide, making baked goods light and fluffy ## Footnote Commonly referred to as baking soda.
37
What is the significance of sodium and potassium in biological systems?
They are essential for **nerve signal transmission** and **cellular functions** ## Footnote Sodium ions **regulate fluid balance** and potassium ions **activate enzymes.**
38
What is the typical concentration of sodium and potassium in blood plasma?
Sodium is 143 mmolL–1, potassium is 5 mmolL–1 ## Footnote These gradients are maintained by the sodium-potassium pump.
39
What defines the electronic configuration of alkaline earth metals?
[noble gas] ns2 ## Footnote They have two electrons in the s-orbital of the valence shell.
40
What is the atomic symbol for Calcium?
Ca
41
What is the atomic number of Beryllium?
4
42
What is the atomic mass of Strontium in g mol–1?
87.62
43
What is the electron configuration for Magnesium?
[Ne] 3s2
44
What is the first ionization enthalpy of Barium?
503 kJ mol–1
45
What happens to the atomic and ionic radii of alkaline earth metals as atomic number increases?
They increase
46
True or False: The first ionization enthalpies of alkaline earth metals are lower than those of corresponding Group 1 metals.
False
47
Fill in the blank: The hydration enthalpy of alkaline earth metal ions _____ with increase in ionic size down the group.
decreases
48
What color does Calcium impart to a flame during a flame test?
brick red
49
What is the general trend for the melting and boiling points of alkaline earth metals compared to alkali metals?
Higher
50
How do alkaline earth metals react with water?
Form hydroxides with increasing vigour
51
What is the typical structure of the oxides formed by alkaline earth metals?
Rock-salt structure (Except BeO)
52
Which alkaline earth metal hydroxide is amphoteric?
Beryllium hydroxide (Be(OH)2)
53
What is the predominant oxidation state of alkaline earth metals?
Dipositive (M2+)
54
What is the solubility trend of alkaline earth metal carbonates in water?
Decreases with increasing atomic number
55
What is the major use of Beryllium in industry?
Manufacture of alloys
56
True or False: All alkaline earth metals readily react with acids to liberate dihydrogen.
True
57
What is the hydration enthalpy trend of alkaline earth metals?
Be2+ > Mg2+ > Ca2+ > Sr2+ > Ba2+
58
What is the chemical formula for the reaction of alkaline earth metals with halogens?
M + X2 → MX2
59
What is the coordination number of Beryllium?
Four
60
What type of bond predominates in beryllium compounds?
Covalent
61
Fill in the blank: Beryllium hydroxide dissolves in excess of alkali to give a _____ ion.
beryllate ([Be(OH)4]2–)
62
What is the reactivity trend of alkaline earth metals as you move down the group?
Increases
63
What is a unique characteristic of Beryllium compared to other alkaline earth metals?
It shows anomalous behavior
64
What is the common structure of beryllium halides?
Covalent and soluble in organic solvents
65
What is the thermal stability trend of alkaline earth metal hydroxides?
Increases with increasing atomic number
66
What is the chemical formula for the thermal decomposition of alkaline earth metal nitrates?
2M(NO3)2 → 2MO + 4NO2 + O2
67
What is a similarity between beryllium and aluminium regarding acid resistance?
Both are not readily attacked by acids due to the presence of an oxide film on the surface of the metal.
68
What ion does beryllium hydroxide form when dissolved in excess alkali?
[Be(OH)4]2–
69
What is the structure of the chlorides of beryllium and aluminium in the vapor phase?
Cl– bridged chloride structure
70
What role do beryllium and aluminium chlorides play in organic chemistry?
They are strong Lewis acids and used as Friedel Craft catalysts.
71
What complex ions do beryllium and aluminium tend to form?
* BeF42– * AlF63–
72
What are some important compounds of calcium?
* Calcium oxide * Calcium hydroxide * Calcium sulphate * Calcium carbonate * Cement
73
How is calcium oxide (CaO) commercially prepared?
By heating limestone (CaCO3) in a rotary kiln at 1070-1270 K.
74
What happens to calcium carbonate when heated to 1200 K?
It decomposes to evolve carbon dioxide.
75
What is the chemical reaction for the formation of calcium hydroxide from calcium oxide?
CaO + H2O → Ca(OH)2
76
What is slaking of lime?
The addition of a limited amount of water to break the lump of lime.
77
What is the product formed when calcium hydroxide reacts with carbon dioxide?
Calcium carbonate (CaCO3)
78
What is the composition of Portland cement?
* CaO, 50-60% * SiO2, 20-25% * Al2O3, 5-10% * MgO, 2-3% * Fe2O3, 1-2% * SO3, 1-2%
79
What is the purpose of adding gypsum to cement?
To slow down the process of setting.
80
What biological roles do magnesium and calcium play in the human body?
* Magnesium is a cofactor for ATP-utilizing enzymes * Calcium is crucial for bone structure, neuromuscular function, and blood coagulation.
81
What is the significance of the 'diagonal relationship' in the periodic table?
It refers to the similarities in properties between the first element of each group and the second element of the next group.
82
What are the characteristics of alkali metals?
* Silvery white * Soft * Low melting * Highly reactive
83
How do the compounds of alkali metals primarily exist?
Predominantly ionic
84
What is the typical reaction of calcium carbonate with dilute acids?
CaCO3 + 2HCl → CaCl2 + H2O + CO2
85
What is the primary use of calcium oxide?
As a primary material for manufacturing cement.
86
What happens when Plaster of Paris is mixed with water?
It forms a plastic mass that hardens in 5 to 15 minutes.
87
Why are alkali metals not found in nature?
They are highly reactive and readily form compounds.
88
What is the main pigment for light absorption in plants?
Chlorophyll, which contains magnesium.
89
How does bone function in relation to calcium?
Bone is continuously being solubilised and redeposited.
90
What is the average composition ratio of silica to alumina for good quality cement?
Between 2.5 and 4.
91
What is the significance of the calcium concentration in plasma?
It is regulated by calcitonin and parathyroid hormone.
92
Why is a solution of Na2CO3 alkaline?
It produces hydroxide ions in solution due to anionic hydrolysis ## Footnote The carbonate ions react with water to form bicarbonate and hydroxide ions, making the solution alkaline.
93
How are alkali metals prepared?
By electrolysis of their fused chlorides ## Footnote This method involves passing an electric current through molten salts of the alkali metals.
94
Why is sodium more useful than potassium?
Sodium has a wider range of applications and is more abundant ## Footnote Sodium is used in various industries, including chemical manufacturing and as a key ingredient in table salt.
95
Write the balanced equation for the reaction between Na2O2 and water.
2 Na2O2 + 2 H2O → 4 NaOH + O2 ## Footnote Sodium peroxide reacts with water to produce sodium hydroxide and oxygen.
96
Write the balanced equation for the reaction between KO2 and water.
4 KO2 + 2 H2O → 4 KOH + 3 O2 ## Footnote Potassium superoxide reacts with water to produce potassium hydroxide and oxygen.
97
Write the balanced equation for the reaction between Na2O and CO2.
Na2O + CO2 → Na2CO3 ## Footnote Sodium oxide reacts with carbon dioxide to form sodium carbonate.
98
Why is BeO almost insoluble but BeSO4 is soluble in water?
BeO has a strong covalent nature and low solubility, while BeSO4 is more soluble due to its ionic nature ## Footnote The sulfate ion can stabilize the beryllium ion in solution.
99
Why is BaO soluble but BaSO4 is insoluble in water?
BaO is ionic and dissolves, while BaSO4 has a strong lattice energy making it insoluble ## Footnote The sulfate ion forms strong bonds with barium, which prevents solubility.
100
Which alkali metal has the least melting point?
Cs ## Footnote Cesium has the lowest melting point among alkali metals.
101
Which alkali metal gives hydrated salts?
Li ## Footnote Lithium is known to form hydrated salts due to its small ionic size and high charge density.
102
Which alkaline earth metal carbonate is thermally the most stable?
BaCO3 ## Footnote Barium carbonate has greater thermal stability compared to other alkaline earth metal carbonates.
103
Fill in the blank: The melting point of Cs is _______.
the least among alkali metals ## Footnote This is due to its large atomic size and weak metallic bonding.
104
True or False: LiI is more soluble than KI in ethanol.
True ## Footnote The solubility difference is attributed to the varying interactions between the ions and the solvent.

Inorganic Chemistry (10 decks)

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