PPT 4.5 Metallic bonding: Metal atoms lose valence electrons to achieve the electronic structure of the nearest noble gas and become positive ions. The lost electrons are delocalised and form a sea of electrons. The metallic bond is the electrostatic force of attraction between the positive ions and delocalised electrons. This sea of electrons prevents the repulsion between positive metal ions and hold them together.
The metallic bond strength depends on the number of valence electrons of the metal atom and the size of the metal atom/ion.
Smaller the size greater the strength.
Greater the valence electrons greater the strength.
Na has stronger bond than Mg since it has smaller size and same number of valence electron.
Metals are good conductors of heat and electricity since electricity is flown in the form of current by free/delocalised electrons. On passing electric current, the delocalised electrons move towards the positive pole. This movement causes the metals to heat when electricity is passed.
Metals are malleable which means they can be hammered into sheets.
Metals are also ductile which means they can be drawn into wires.
Metals have generally high MP. MP decreases on moving down the group as the size increases and metallic bond strength decreases.
W(filament of electric bulb) has MP of 34220C while Hg( only liquid metal) has MP of -38.80C.
An alloy is the homogeneous mixture of two or more metals except steel which contains carbon as well.
Example: Steel is an alloy of Fe and C, Brass is an alloy of Cu and Zn, Bronze is an alloy of Cu and Sn.
Different metals have different atomic size hence the metal lattice gets distorted and atoms can not slide which changes the properties. The alloys thus are more stronger and harder which means less malleable and ductile.
With This PPT 4.5 Metallic bonding, I hope you have understood the concept.
You can refer Ionic bonding topic.