质量数(massnumber)是指中性原子中,将原子内所有质子和中子的相对
2119百达翡丽精致精钢圆八角形年历自动腕表备日期星期
potassium, isotope ofmass 39
viscosity average. weight average= mw. number average = mn.
元素周期表及原子核外排布规律
Tips:Do Not Provide
Personal Loans: Go Easy On Your Finances
Finance, Finance, Finance, Foreign Exchange, Stocks, Currency Circle, Venture Capital, Bitcoin, ICO...