Questions about the strange character of antimatter Its been a few days and i have just been introduced to the concept of antimatter. Every Speck of matter in  the world has its anti form basically that we have antimatter whenever we have matter. But I have two questions on antimatter:


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*Why is that there is less antimatter in this world than matter?If antimatter is just the opposite of matter there should be as much antimatter as there is matter. Also why did we find that antimatter existed in this world so late if it just the opposite of matter then it should have been found way back? And if there is antimatter in the same amount as matter why cant we see it? 

*If I make a periodic table out of antimatter what will be the properties of the respective elements?
 A: 
Every Speck of matter in the world has its anti form basically that we have antimatter whenever we have matter.

This is not exact; in theory any form of matter can have its corresponding form of antimatter, but the universe we live in is predominantly made up of matter. This is an experimental observation because when matter meets antimatter there is a violent destructive interaction, resulting in radiation and elementary particles flying away.
1)Our planetary system is matter, checked by landing on the moon and landing probes on Mars, and the lack of the characteristic radiation lines from annihilation of matter with antimatter.
2) this is true also by observation with our galactic system as we would see the results of annihilating matter.
It is more hypothetical for clusters of galaxies but again there is no observation that would argue for an antimatter galaxy as again the radiation where galaxy meets antigalaxy would be characteristic.

Also why did we find that antimatter existed in this world so late if it just the opposite of matter then it should have been found way back? And if there is antimatter in the same amount as matter why cant we see it? 

As I said, it is the proof that our universe is made of matter, and antimatter comes in elementary particle interactions from cosmic rays to laboratories and was found less than 100 years ago. The standard model of particle physics has very small violation of the symmetry between particles and antiparticles, and when it is used in the cosmological models of the creation of the universe extra assumptions must enter to end up with a mainly matter universe from an original  almost symmetric matter/antimatter. That is  one of the main reasons why new theoretical models are proposed and are being studied in experiments with particle physics. We have still to understand the whys and hows of this asymmetry.

If I make a periodic table out of antimatter what will be the properties of the respective elements?

It will be the symmetric one, where we have electrons there will be positrons and the nuclei will be made up with antineutrons and antiprotons. Antihydrogen has been created in the laboratory. If something unexpected from the symmetry is detected  it may be that the studies will contribute in understanding the strong asymmetry in our observable  universe.
A: 1) Nobody knows. It's one of the major unsolved problems in physics today. Our best guess is that it is not true that antimatter is "just the opposite"--probably there is some slight asymmetry between them. But we haven't really found what it is yet, or at least haven't found anything that explains the discrepancy. Despite the huge difference in the modern world, the difference fundamentally can be very small. You can go back to early-universe cosmology and figure out how small the asymmetry needs to be. According to my Statistical Mechanics book (Pathria 3rd ed.), we can explain our current antiatter/matter asymmetry if for every 1.7 billion positrons (anti-electrons) in the early universe, there was 1.7 billion + 1 electrons. So it's very small.
2) Nobody knows. Probably the same as for the matter periodic table. Chemistry is determined by the behavior of electrons, and it seems likely that the positrons in anti-atoms would behave identically. That said, nobody's checked yet. People have made anti-hydrogen, and so far as I know haven't been able to observe differences from regular hydrogen. But these are new experiments, so who knows. We will likely never be able to form the much heavier anti-elements.
