EasyChemistryHigh School (9–10)GeneralStructure of the Atom › Subatomic Particles and Atomic ModelsConceptual

Name the particle in each case. It is negative and has almost no mass.

Try it on paper first. A hint, the key idea and the worked solution are here when you need them.

Name the particle in each case.

It is negative and has almost no mass.
It is in the nucleus and has no charge.
It is in the nucleus and has a charge of $+1$ .
Its number decides which element the atom is.

Which of the three particles was found last, and why was it the hardest to find?

Need a reminder? The key ideaShow

An atom has three kinds of particle. The proton has a charge of $+1$ and a mass of about $1\ \text{u}$ . The neutron has no charge and a mass of about $1\ \text{u}$ . The electron has a charge of $-1$ and a mass of only $\dfrac{1}{1836}\ \text{u}$ . The charge of one proton is $1.6 \times 10^{-19}\ \text{C}$ .

The worked solution

Have you tried it?

Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.

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← An atom of calcium-40 has 20 electrons. Each electron has a mass of 1/1836 u.The charge of one proton is 1.6 × 10⁻¹⁹ C. →

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