Subject: why is osmium heavier than lead when lead has more p+, e- and neutrons

I was in chemistry class (grade 11) and I noticed on my St Clair periodic 
table that osmium (element #76) has fewer protons, neutrons and electrons 
than lead yet weighs more (almost twice as much Os-22.59 grams per cubic 
cm and lead-11.34 grams per cubic cm). At first I thought it was a mistake 
but found out from a chemical dictionary that it was right. Then I asked 
Mr. Bailey my chemistry teacher, he didn't know so I asked all other 
chemistry teachers and same results there. I dont see how more of 
something can make a thing weigh less than something that has less yet 
weighs more. Do you? 

Re: why is osmium heavier than lead when lead has more p+, e- and neutrons