How much time in average does it take for an simple PC to create block? Let's say I have simple computer (CPU- Intel i7 for example), and I start mining blocks in the bitcoin network. How much time in average does it take to create 1 block? (1 per week? 1 per month? 1 per 3 month? ....)

And if the answer is 1 per month or something like that, why not all the world participate in the mining process? it seems like an easy money to earn ...
And that's why I think that I missed something in my knowledge

Thanks in advance!
The answer is constantly changing, but this is something you can calculate yourself.


Look up the current Bitcoin difficulty value.  Right now it is 460,769,358,091.  Let's use scientific notation: 4.6e11.
The difficulty determines the average number of hashes needed to mine one block.  A minimum difficulty of 1 corresponds to 2^32 = 4.3e9 hashes, so we need an average of 4.6e11 * 4.3e9 = 2.0e21 hashes to mine a block.  (More precisely, each hash performed has a probability of 1 in 2.0e21 of successfully creating a block.)
Look up the approximate hash rate for the hardware you have in mind.  For CPUs and GPUs there is a table here; ASIC devices can be found here.  According to that table, a Core i7 2600 CPU can do 23.9 MHash per second, or 2.3e7 hashes per second.  Maybe you are starting to see the problem.
2.0e21 / 2.3e7 = 8.7e13.  That is the average number of seconds your computer will need to mine one block.  It is about 2.7 million years.


This should give you a sense as to why all Bitcoin mining is now done with specialized ASIC hardware, which is many orders of magnitude faster and more energy-efficient.