Tag: group 1 elements: alkali metals

Quizzes (0) Questions (69)

Questions Related to group 1 elements: alkali metals

Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) anomalous properties of lithium group 1 elements: alkali metals properties of s block elements

Li resembles to element X which is not the member of alkali metals. The group of X is?

  1. II

  2. III

  3. IV

  4. I
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Li resembles to element X which is not a member of alkali metals. The group of X must be II group, because certain elements of 2nd period show similarity with their diagonal elements in the 3rd period as shown below : Thus, Li resembles Mg, Be resembles Al and B resembles Si. This is called diagonal relationship and is due to the reason that these pairs of element have almost identical ionic radii and polarizing power (i.e. charge/size ratio). Element of second period are known as bridge elements.

So Li is I st group element and the diagonal element Mg is II nd group element.
Hence option A is correct.

Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) anomalous properties of lithium group 1 elements: alkali metals properties of s block elements

$Mg$ and $Li$ and similar in their properties due to:

  1. same $\dfrac {e}{m}$ ratio

  2. same electron affinity

  3. same group

  4. same radius
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$Li$ and $Mg$ show diagonal relationship due to the similarity in size (radius), electronegativity, ionisation enthalpy and charge/radius ratio.

Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) anomalous properties of lithium group 1 elements: alkali metals properties of s block elements

Li resembles to element X which is not the member of alkali metals.
The element X is :

  1. Mg

  2. Be

  3. Ca

  4. B
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Li resembles to element X which is not the member of alkali metals. The element X is Mg. This is due to diagonal relationship. Certain elements of 2nd period show similarity with their diagonal elements in the 3rd period as shown below : Thus, Li resembles Mg, Be resembles Al and B resembles Si. 


This is called diagonal relationship and is due to the reason that these pairs of element have almost identical ionic radii and polarizing power (i.e. charge/size ratio). Element of second period are known as bridge elements.   
Hence option A is correct.

Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) anomalous properties of lithium group 1 elements: alkali metals properties of s block elements

Lithium borohydride, $LiB{H} _{4}$, crystallizes in an orthorhombic system with four molecules per unit cell. The unit cell dimensions are $a=6.0\mathring { A } ,b=4.4\mathring { A } ,c=7.5\mathring { A } $. The density of crystals is
$\left( Li=7,B=11,{ N } _{ A }=6\times { 10 }^{ 23 } \right) $

  1. $0.74g/{cm}^{3}$
  2. $1.48g/{cm}^{3}$
  3. $0.37g/{cm}^{3}$
  4. $0.90g/{cm}^{3}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Using the density formula: d = (Z × M) / (NA × a × b × c). With Z=4, M=22 g/mol (7+11+4), NA=6×10^23, dimensions in Angstroms (1 Å = 10^-8 cm): volume = 6×4.4×7.5 × 10^-24 cm^3 = 198×10^-24 cm^3. Mass = (4 × 22)/(6 × 10^23) g = 1.47×10^-22 g. Density = 1.47×10^-22 / 198×10^-24 = 0.74 g/cm^3.

Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) anomalous properties of lithium group 1 elements: alkali metals properties of s block elements

Lithium shows similarities with magnesium in its chemical behaviour because :

  1. similar size, greater electronegativity and lower polarising power

  2. similar size, same electronegativity, and lower polarising power

  3. similar size, same electronegativity and similar high polarising power

  4. none of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Lithium shows similarities with magnesium in its chemical behaviour because they have similar size and charge/size ratio. They have similar electronegativity.


This type of diagonal similarity is commonly referred to as diagonal relationship in the periodic table.

Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) anomalous properties of lithium group 1 elements: alkali metals properties of s block elements

In certain matters, lithium differs from other alkali metals; the main reason for this is :  

  1. small size of lithium atom and $Li^+$.
  2. extremely high electropositivity of $Li$.
  3. greater hardness of $Li$.
  4. hydration of $Li^+$ ion.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In certain matters, lithium differs from other alkali metals(anamalous property); the main reason for this is small size of lithium atom and $Li^+$ and high polarizing power.

Hence option A is correct.

Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) anomalous properties of lithium group 1 elements: alkali metals properties of s block elements

In certain matters, lithium differs from other alkali metals, the main reason for this is:

  1. Small size of lithium atom and $Li^+$ ion
  2. Extremely high electro positivity of $Li$
  3. Greater hardness of $Li$
  4. Hydration of $Li^+$ ion
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The chemistry of lithium shows several differences from that of the rest of the group as the small lithium cation polarises anions and gives its compounds as the more covalent character.

Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) anomalous properties of lithium group 1 elements: alkali metals properties of s block elements

Which of the following pairs shows diagonal relationship?

  1. $Na$ and $Mg$
  2. $Li$ and $Mg$
  3. $Li$ and $Na$
  4. $Al$ and $C$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A diagonal relationship is said to exist between certain pairs of diagonally adjacent elements in the second and third periods of the periodic table. Thus, $Li$ and $Mg$ are diagonally related.

Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) anomalous properties of lithium group 1 elements: alkali metals properties of s block elements

Diagonal relationship is due to:

  1. identical ionization potential

  2. identical electron negativity

  3. identical sizes of ions

  4. same valence shell configuration
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Option $(C)$ is correct.

The diagonal relationship is due to identical sizes of ions.
On moving rightward a period of the periodic table, the size of the atoms decreases, and on moving down a group the size of the atoms increases. Similarly, on moving rightward a period, the elements become more electronegative, whereas on moving down the group the element becomes more positive. These two factors work in opposite direction. Hence the elements that are present diagonally to each other have similar properties like atomic size, electronegativity, density, chemical properties of compounds.

Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) anomalous properties of lithium group 1 elements: alkali metals properties of s block elements

What is the correct formula for lithium fluoride?

  1. $LiF$
  2. ${Li} _{2}{F} _{2}$
  3. ${Li} _{3}{F} _{9}$
  4. $Li{F} _{7}$
  5. ${Li} _{7}{F} _{19}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$LiF$ is the correct formula for lithium fluoride. $Li$ has a +1 charge and $F$ has a -1 charge so, when they come together, to form $LiF$ having an ionic bond.