4.4.1 Atoms and isotopes

What is the radius of an atom?

1 × 10-10 metres

What is the basic structure of an atom?

A positively charged nucleus with both protons and neutrons surrounded by negatively charged electrons

What is the radius of a nucleus?

Less than 1/10000 of the radius of an atom

Where is most mass of an atom concentrated?

In the nucleus

How do electrons move further from the nucleus?

By absorbing electromagnetic radiation

How do electrons move closer to the nucleus?

By emitting electromagnetic radiation

What’s the number of protons in an atom of element called?

The atomic number

What is the total number of protons and neutrons in an atom?

The mass number

What is an isotope?

An atom with the same number of protons and a different number of neutrons

How is an ion formed?

When an atom gains or loses electrons

What is the process of an atom becoming an ion called?

Ionization

Before the discovery of the electron, what was believed about the atom?

The atom was believed to be indivisible

How did the plum pudding model describe the atom?

It was a ball of positive charge with negative electrons embedded in it

What was the conclusion from the alpha particle scattering experiment?

The mass of an atom was concentrated at the centre and the nucleus was charged

What was the name of the model that replaced the plum pudding model?

The nuclear model

How did Bohr adapt the nuclear model?

By suggesting that electrons orbit the nucleus at specific distances

What did James Chadwick prove the existence of?

Neutrons within the nucleus