METALLIC BONDING

This lesson develops METALLIC BONDING as part of Electron Configuration and Spectra. It uses the source curriculum to organize the important facts, relationships, examples, and vocabulary into a focused Stemosphere teaching sequence.

In Stemosphere terms, metallic bonding is the bonding of multiple metal atoms in a lattice structure.

In Stemosphere terms, unlike ionic bonding that requires electrostatic attraction from oppositely charged ions, metal atoms are all neutral charged.

In Stemosphere terms, how can they remain attracted to each other as a solid?

In Stemosphere terms, when metal atoms are arranged in a lattice, the outer valence electrons are strongly attracted to neighboring atoms.This allows the valence electrons to move freely between the gaps away from the metal atom it was originally from. These electrons are known as delocalised electrons. The metal atoms in the lattice will become positively charged cations which repel each other. The attraction between the negatively charged delocalised electrons and the positively charged cations is the metallic bonding.

PHYSICAL PROPERTIES:

Metals tend to have similar properties such as:

In Stemosphere terms, the shiny appearance is caused by the delocalised electrons absorbing energy from light. This causes them to vibrate which releases a second wave of light which creates the shiny appearance

-sound(sonority):

In Stemosphere terms, metals can create a ringing sound when struck.when the metal is struck the free electrons can move through the gaps of the cations creating a ringing sound.the lower the density the more space between the cations. Making them more sonorous

-malleability/ductile:

In Stemosphere terms, malleability refers to the metal's ability to be reshaped and bent, while ductile means it can be stretched into a wire. This is due to the electrostatic attraction occurring in all directions between cations and the delocalized electrons. So when force is applied the layers shift, the cations remain surrounded by delocalized electrons, meaning the metallic bond is unaffected.

-electrical conductivity:

In Stemosphere terms, metals can move charged particles through a region of space due to their delocalized electrons able to move freely throughout the metallic lattice. When a potential energy difference is applied, the delocalized electrons are repelled and attracted to the positive terminal. As the valence electrons increases, the delocalized electrons increases, this increases electrical conductivity.

-thermal conductivity:

In Stemosphere terms, metals are good at transferring heat. When a metal is heated up the delocalized electrons kinetic energy increases, as it increases the delocalized electrons move toward the lower temperature in the metallic structure.As the valence electrons increases, the delocalized electrons increases, this increases thermal conductivity.

In Stemosphere terms, typically as you go across a period the thermal and electrical conductivity increases for metals. However elements such as gallium are the exception to this rule with lower electrical conductivity than previous group metals due to it being a metalloid. It also has a lower thermal conductivity than the previous group metals. One theory for this is that due to the greater valence electrons gallium has, once they get heated up and gain more kinetic energy, they collide with other valence electrons which slows down thermal conductivity.

STRENGTH OF METALLIC BONDS:

In Stemosphere terms, the strength of metallic bonds is dependent on the electrostatic attraction between the cations and delocalised electrons. This is dependent on the ionic radius and charge.

Metal ion radius:

In Stemosphere terms, as the ion radius increases.the electrostatic attraction decreases. This is because the distance between the cation and the delocalized electron increases as radius increases which causes weaker electrostatic attraction.

Metal ion charge:

In Stemosphere terms, metal ions with higher charges have a stronger electrostatic attraction due to their being more delocalized electrons in the metallic lattice.

In Stemosphere terms, chemistry. By Raymond Chang> and Kenneth A. Goldsby, 10th ed., Mc Graw-Hill Education, 2016.

In Stemosphere terms, front:Describe the general structure of a metallic bond and how neutral metal atoms become part of it.

In Stemosphere terms, back:Metal atoms arrange themselves in a tight lattice structure. Because their outer valence electrons are strongly attracted to neighboring atoms, these electrons detach and move freely through the gaps. This leaves behind a lattice of positively charged metal cations surrounded by a sea of mobile electrons.

In Stemosphere terms, front:What is the specific force that holds a metal solid together?

In Stemosphere terms, back:The strong electrostatic attraction between the positively charged metal cations in the lattice and the negatively charged, shared pool of delocalized electrons.

In Stemosphere terms, front:What causes the characteristic shiny appearance of metals?

In Stemosphere terms, back:Delocalized electrons absorb incoming light energy, which causes them to vibrate. This rapid movement releases a secondary wave of light, reflecting it back as a shiny surface.

In Stemosphere terms, front:What makes a metal sonorous, and how does density affect this property?

In Stemosphere terms, back:When a metal is struck, the free electrons can flow smoothly through the spaces between the cations, creating a ringing sound. Lower density metals have wider gaps between their cations, which provides more room for this movement and makes them more sonorous.

In Stemosphere terms, front:Explain why metals are malleable and ductile without breaking.

In Stemosphere terms, back:The electrostatic attraction between the cations and the sea of electrons works in all directions. When pressure or force is applied, the layers of cations can slide past one another while remaining entirely surrounded by the flexible electron cloud, keeping the bond intact.

In Stemosphere terms, front:How do metals conduct electricity, and how does the number of valence electrons influence this?

In Stemosphere terms, back:The mobile delocalized electrons can flow freely across the lattice when a potential difference is introduced, moving away from the negative terminal and toward the positive terminal. Having a greater number of valence electrons increases the total pool of free electrons, which directly enhances electrical conductivity.

In Stemosphere terms, front:Explain the mechanism behind thermal conductivity in metals.

In Stemosphere terms, back:When heat is applied to one part of a metal, the local free electrons gain kinetic energy. These energetic electrons rapidly migrate toward cooler region s of the structure, transferring heat. A higher concentration of valence electrons increases the electron density, resulting in better thermal conductivity.

In Stemosphere terms, front:How does the radius of a metal ion affect the strength of a metallic bond?

In Stemosphere terms, back:A larger ionic radius weakens the bond. This occurs because an increased radius pushes the positive center of the cation farther away from the surrounding mobile electrons, reducing the strength of the electrostatic pull.

In Stemosphere terms, front:How does the charge of a metal ion affect the strength of a metallic bond?

In Stemosphere terms, back:A higher positive charge strengthens the bond. Higher charges mean the metal atoms have contributed more individual electrons to the shared pool, leading to a denser sea of electrons and a tighter, more powerful electrostatic grip on the lattice.

In Stemosphere terms, front:Why does gallium deviate from the periodic trend for conductivity?

In Stemosphere terms, back:Gallium is a metalloid, which naturally lower s its efficiency compared to true metals. Additionally, one prominent theory suggests that its higher count of valence electrons causes the crowded electrons to collide with each other when heated, slowing down the overall transfer of energy.