Which of the following statements are true about metallic bonds?

a. they hold together ionic bonds.

b. they bond a metal to a nonmetal.

c. they bond identical atoms together.

d. they hold together atoms with different electronegative.

B. They bond identical atoms together

Explanation:

Metallic Bond:  This is the bond that exists among the atoms of the metal.  This is a type of electrostatic attraction between conduction electrons of metallic atom and their positively charged metal ions.

                                        (figure attached)

Example:  

Copper is a metallic element and its atoms consist of metallic bond among their selves.  

Options A, B, D are not correct as all states for a kind of ionic bond formation.

Ionic bond:  

It form by the complete transfer of electron from one atom to other

It is formed among two atoms of different electronegativities.

Also metals are electro-positive and non -metals are electro-negative so they form ionic bond.

Example is NaCl where sodium is a metal and Chloride is non-metal and they from ionic bond.

atomic mass = 39

number of neutrons = 20

number of protons= 19

electronic configuration = 1s2 2s2 2p6 3s2 3p6 4s1

the number of electron in first shell = 2

number of electrons in n=3 shell = 8