Two atoms of hydrogen combine with one atom of oxygen to form a molecule of water.

两个氢原子和一个氧原子结合组成一个水分子。

《牛津词典》

A molecule of water consists of two atoms of hydrogen and one atom of oxygen.

水分子由两个氢原子和一个氧原子构成。

《牛津词典》

An atom itself is a complete whole, with its electrons, protons and neutrons and other elements.

原子本身是个整体，含电子、质子、中子以及其他组成部分。

《柯林斯英汉双解大词典》

The researchers found the presence of carbon thirteen, a version of the carbon atom that is usually found in space.

VOA: special.2009.09.30

Let's look at the energetics of one of those electrons crashing into a hydrogen atom inside the gas tube.

我们一起来考察一下,其中的一个电子的能量,在阴极射线管中,撞击到氢原子上。

麻省理工公开课 - 固态化学导论课程节选

OK, then it says draw a single bond from each surrounding atom to the central atom, and subtract two valence electrons.

后将中心原子与其相邻原子之间,连上单键，然后减掉2个价电子。

麻省理工公开课 - 固态化学导论课程节选

They were structurally similar to cytisine in many ways, sharing the location of a nitrogen atom in a particular place on a pair of bicycle-like carbon rings.

FORBES: Tobacco-Free

He found a 17-year-old paper written by University of Maryland researcher Paul Mazzochi that mentioned how moving a nitrogen atom in a morphine molecule caused its morphinelike properties to disappear--and also made it poisonous, just like nicotine.

FORBES: Tobacco-Free

These are an amine group, an acid group (hence the name), a hydrogen atom, and a fourth chemical group that can be any one of 20 different clusters of atoms.

ECONOMIST: Folding stuff