All the isotopes of a given element have the same number of protons, but differ in their number of neutrons, and hence in their atomic mass.

给定元素的所有同位素都含有相同的质子数，但它们的中子数不同，因此它们的原子质量也不同。

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Then I have the total mass of A divided by the number of moles of A.

然后是A的总质量,除以A的摩尔数。

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A number of studies have shown that the presence of a critical mass of women in senior jobs is positively correlated with a company's performance and possibly with higher profits.

一些研究表明，决策层女性占关键多数可能和公司业绩改善、利润提高有关。

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That quantity in parenthesis, I have a mass which is a positive number. Something raised Something raised to the fourth power has got to be positive.

顺便说一句,质量这个量是个正数,四次方的值,肯定是正数。

麻省理工公开课 - 固态化学导论课程节选

12 That gives it a mass number of 312.

所以它的质量数为。

麻省理工公开课 - 固态化学导论课程节选

We had a great number of mass.

我们有很多受众。

斯坦福公开课 - Twitter之父Jack.Dorsey演讲：好奇和灵感的力量课程节选

Around the world palm computer use is poised to hit critical mass as a number of new technologies coalesce.

CNN: Cross My Palm With Silicon

Some three and a half million people go to Mass every week - a big number despite the declines.

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He believes he could face charges there over the release of top secret documents by Wikileaks, whose publication of a mass of leaked diplomatic cables has embarrassed a number of countries.

BBC: Julian Assange police guard cost nears ?3m