What is the mass mumber of an element?ps:Please answered in EnglishI want the define of "mass mumber of an element"

what is the difference between mom and mum The mass of 0.02mol of a substance is 0.88g1.what is the molar mass of this substance?2.what is its chemical formula? 尽量“人性化”一点!0.4 of the mass of Mark is the same as 0.3 that of Mathew.What is the ratio of the mass of Mark to total mass? What is the mass mumber of an element?ps:Please answered in EnglishI want the define of mass mumber of an element The atomic mass of copper is 63.55 amu.There are onlytwo isotopes of copper,63Cu with a mass of 62.93 amu and65Cu with a mass of 64.93 amu.What is the percentageabundance of each of these two isotopes? the empirical forumla of a compound is no2,its molecular mass is 92g/mol.what is its molecular formula? the mass of a magazine is 270g.A dictionary is 3 times as heavy as the magazine.what is the total mass of the magazine and the dictionary? 质谱分析求解From the Mass Spectra below,what functional group does thiscompound have? What is the mass of this molecule?(assume all of thecompound spectra is present)实在是分析不出来, THE MASS the mass 电子电量和质量之比是多少?急!what is the electron charge-over-mass ratio?是多少啊?急 what is the mass number of an atom that has 28 neutrons?请在5月24号之前回答 1.In a group of six people,two have a mass of 60kg while three have a mass one and half times that.what is the mass of the sixth person if the average group mass is 70kg?2.There are x dimes and y nickels in bag A and x nickels and y dimes in bag B.Th A highly volatile substance initially has a mass of 1200g and its mass is reduced by 12% each second.Q1.Write a formula that gives the mass of the substance(m) at time(t) seconds.Q2.Rearrange this formula to make t the subject.Q3.What mass remains af what is the weather like tomorrow ,mum.it is old and snowy.great i like().what is the weather like tomorrow ,mum.it is cold and snowygreat i like()。 What is your Mum's response to the plan S___ as she is ,she nodded her head this time the empirical forumla of a compound is no2,its molecular mass is 92g/mol.what is its molecular formula?help me do this! The mass of the Great Pyramid is 557t greater than that of the Leaning Tower of Pise.Stone Hengehas a mass of 2695t which is 95t less than the Leaning Tower of Pisa.There once was a Greater Pyramid.What was the mass of the Greater Pyramid?