What has more particles a mole of Helium atoms or a mole of water (H2O)?

A mole of water.

Explanation:

Helium is composed of stable atoms. That means you just have 1 mole particles. But with water, you have the molecules - 1 mole, and the atoms. There are 3 atoms in a molecule of water, so there are 3 mol atoms in 1 mol of H2O.

Helium: 1 mol particles

Water: 1 mol molecules + 3 mol atoms = 4 mol of distinguishable particles

it is to be noted that an alpha particle is an helium nucleus. so it contains 2 protons 2 neutrons and has a mass number of 4. when alpha decay particles are ejected from the nucleus it gets transformed into an atom which has atomic number less than 2 and a mass number less than 4.

an equation that could represent alpha decay is radium 226 decay of alpha particle forms radon 222.

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