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Diagonal relationship in periodic table

Diagonal relationship in periodic table

Bimal Raut(https://chemistnotes.com/author/bimalraut/) May 25, 2022
Periodic table (https://chemistnotes.com/inorganic_chapter/periodic-table/)

Table of Contents
1. Lithium and Magnesium diagonal relationship
2. Diagonal relationship between Beryllium and Aluminium
3. Diagonal relationship between Boron and Silicon
4. Diagonal relationship Video
5. FAQs/MCQs
5.1. diagonal relationship definition
5.2. diagonal relationship examples
5.3. diagonal relationship is shown by

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5.4. cause of diagonal relationship

6. References

Diagonal relationship is a resemblance of the properties of the elements of 2nd period with
diagonally opposite members lying in the 3rd period. The two diagonal elements showing
similarities in properties are called diagonal pairs. It is the most important feature of the earlier
element of the second period (Li, Be, & B) that they resemble more with the elements lying on
the right-hand side in the third-period element (i.e. diagonally opposite element) than with
another member of their own group. Thus Li resembles more in its properties with Mg than
other alkali metals. Similarly, Be shows similarity with Al, and B resemble Si.

Period Group 1 (IA) Group 2 (IIA) Group 13 (IIIA) Group 14 (IVA)

2nd Li Be B C

3rd Na Mg Al Si

Table: Pairs of diagonal elements

The diagonal relationship arises due to resemblance in properties such as atomic size,
ionization energy (https://chemistnotes.com/inorganic/ionization-energy-and-ionization-
potential/), electronegativity (https://chemistnotes.com/inorganic/electronegativity/), and
polarizing power of their corresponding cations.

Lithium and Magnesium diagonal relationship

The diagonal relationship between Li and Mg is due to:

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• Electronegativity of both the elements are almost identical (Li = 1.0, Mg = 1.2).
• Atomic (Li = 1.34 Å, Mg = 1.30 Å) and ionic radii (Li = 0.68 Å, Mg = 0.65 Å) are nearly
identical in both elements.
The following points illustrate the diagonal relationship between lithium and magnesium:

• Li and Mg are both harder metals with greater melting points than other metals in their
groups.
• When Li and Mg are burnt in the air, they produce the typical oxides Li2O and MgO, which
are just sparingly soluble in water.
• On heating, nitrates, carbonates, and hydroxide compounds of both metals decompose in
the same way.

• Both metals react slowly with H2O to form metallic hydroxides, which generate H2 gas.

• Both metal formates form metallic carbonates and formaldehyde when heated.

Diagonal relationship between Beryllium and Aluminium

The diagonal relationship between Be and Al is due to:

• The electronegativity of both elements is almost identical (Be = 1.5, Al = 1.5).

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• The covalent radii of both elements are identical.

• Both metals possess a weak electropositive character.
• The ratio between cationic charge and cationic size i.e. Be2+ (0.033) and Al3+ (0.044) ions
are almost the same.
The Be and Al diagonal relationship is illustrated by the following points:

Fast download here

• Both metals are typically extracted by electrolytic reduction of their oxides.

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• Both metals i.e. Be and Al is present as beryl, 3BeO.Al2O3.6SiO2 in nature.

• Be+2 and Al+3 ions have a great tendency for forming complexes with ligands. Some of the
examples are: [Be(H2O)4]++, [Al(H2O)6]+3, [AlF6]-3 and so on.
• In combination with halogens, both the metals behave as Lewis acid
(https://chemistnotes.com/organic/acid-and-bases-arrhenius-theory-bronsted-lowery-
theory-lewis-acid-and-bases/). As illustrated below, both BeCl2 and AlCl3 have
bridge/dimeric structures.

• Both the metals combine with N2 and form their nitrides (Be3N2 and AlN). These nitrides
are decomposed by H2O to form metallic hydroxides and ammonia gas is evolved out.

Diagonal relationship between Boron and Silicon

The diagonal relationship between B and Si is due to:

• The electronegativity of both elements is almost identical (B = 2.0, Si = 1.8).

• Both elements have similar cationic charge and cationic size ratio values.
The B and Si diagonal relationship are illustrated by the following points:

• Since both elements are non-metals, they are poor conductors of heat and electricity.
• Most of the compounds of these elements are covalent in nature.
• Both the elements exist in two allotropic forms; amorphous and crystalline. Crystalline
forms of both elements are hard.
• Both the elements can be obtained by reducing their oxides with Mg metal.

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• The oxides of both elements are stable. Because they form boric acid and metasilicic acid
in the water, both oxides are weakly acidic in nature.

Diagonal relationship Video

https://www.youtube.com/watch?v=R4WHZOX7FZw

FAQs/MCQs
diagonal relationship definition
Diagonal relationship is a resemblance of the properties of the elements of 2nd period with
diagonally opposite members lying in the 3rd period.

diagonal relationship examples

Lithium (Li) and magnesium (Mg), beryllium (Be) and aluminum (Al), boron (B), and silicon (Si);
these three pairs show a diagonal relationship.

diagonal relationship is shown by

The diagonal relationship is shown by 2nd (Li, Be, & B) and 3rd (Mg, Al, & Si)-period elements of
the periodic table as they possess similar properties.

cause of diagonal relationship

The resemblance in properties such as atomic size, ionization energy
(https://chemistnotes.com/inorganic/ionization-energy-and-ionization-potential/),
electronegativity (https://chemistnotes.com/inorganic/electronegativity/), and polarizing power
of their corresponding cations are the cause of diagonal relationships.

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Tags: be and al diagonal relationship (https://chemistnotes.com/tag/be-and-al-diagonal-
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diagonal relationship between beryllium and aluminium (https://chemistnotes.com
References
/tag/diagonal-relationship-between-beryllium-and-aluminium/), diagonal relationship between
boron and silicon (https://chemistnotes.com/tag/diagonal-relationship-between-boron-and-
silicon/), diagonal relationship
• Rayner-Canham, Geoffreybetween elements
(22 December (https://chemistnotes.com/tag/diagonal-
2013). Descriptive inorganic chemistry. Overton,
relationship-between-elements/),
Tina (Sixth ed.). New York diagonal relationship between li and mg
(https://chemistnotes.com/tag/diagonal-relationship-between-li-and-mg/),
• Shriver, Duward (2006). Inorganic Chemistry (4th ed.). diagonal relationship
between lithium and magnesium (https://chemistnotes.com/tag/diagonal-relationship-between-
lithium-and-magnesium/), diagonal relationship definition (https://chemistnotes.com
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(https://chemistnotes.com/tag/diagonal-relationship-examples/), diagonal relationship in
periodic table (https://chemistnotes.com/tag/diagonal-relationship-in-periodic-table/), diagonal
relationship is shown by (https://chemistnotes.com/tag/diagonal-relationship-is-shown-by/),
lithium and magnesium diagonal relationship (https://chemistnotes.com/tag/lithium-and-
magnesium-diagonal-relationship/), what is diagonal relationship (https://chemistnotes.com
/tag/what-is-diagonal-relationship/)

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Bimal Raut
(https://chemistnotes.com
/author/bimalraut/)
Bimal Raut is currently doing his
Master's Degree in Chemistry at
Central Department of Chemistry,
Tribhuvan University. He's been
actively involved in several
(https://chemistnotes.com/inorganic/group-13-elements-boron-family-easy-explanation/)
(https://chemistnotes.com/author/bimalraut/)
research projects related to natural
products, nanochemistry, and
Group 13 Elements: Boron Family- Easy Explanation (https://chemistnotes.com/inorganic
/group-13-elements-boron-family-easy-explanation/) computational chemistry. He is
currently working on drug design,
molecular docking, antibody
generation, and assay
development.

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