If nacl has an fcc structure, then why is its coordination number 6 instead of 12?

Metallic crystal in FCC has coordination number 12. NaCl is an ionic crystal having FCC structure in which coordination number of both cation and anion are 6.

can u give me str of nacl

see

is is right

yes see the image....focus on each cation and anion

in diagram you have given, it is difficult to see voids, na is betn the voids na

for coordination number you have to check na...see each Na+ is surrounded by 6 Cl- ions and vice versa

do chlorine atoms touches to each other or not?

as well as na atoms touch each other?

cl to cl ans na to na

The crystalline structure of NaCl is face-centred cubic. The total number of ions present in one unit cell of sodium chloride lattice is 8. It includes 4 Na+ ions and 4 Cl− ions. There are 8 Cl− ions at 8 corners of fcc unit cell (each one contributes one eigth to unit cell) and 6 Cl− ions at 6 face centres  (each one contributes one half to unit cell). Total number of Cl− ions in the unit cell =8×81​+6×21​=1+3=4 Na+ ions occupies octahedral voids. There are 4 octahedral voids in fcc unit cell. Thus, there are 4 Na+ ions in fcc unit cell.

this is explanined for unit cell

when coordination number finding see the image you clearly see how 6:6 CN is there

do Na atoms touch each other or not in this structure?

Na to na?

no sodium ion in center touched by 6 cl ion

see this one , is it right?

yes this is right...bdw these are 3d type crystal structure so better you see ball and stick model of this...may be available on YouTube

is this right for nacl?

for this co ordination no is 12

so im confused

dear why you checking common check for each ion individually and so i told na for this see model of this

https://youtu.be/v8g3CK5kke0 check

check this link for more details http://www.questtutorials.com/media/static/xii/chemistry/02_The%20Solid%20State/04_Structure%20of%20simple%20ionic%20compounds.htm