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The protons of an atom are found in the nucleus of the atom.

# Atomic Structure 1

The study of atomic structure forms a major part of GCSE Chemistry. This includes many aspects such as the sub-atomic particles (protons, neutrons and electrons) and their arrangement within the atoms of different elements; atomic mass; atomic number; positive and negative charge; the nucleus; energy levels or electron shells - to name but a few!. Therefore, we have three quizzes devoted to this particular topic, of which this is the first.

The word atom comes from the ancient Greek word atomos meaning unsplittable or uncuttable. A philospher called Democrites carried out a thought experiment. He imagined taking a piece of rock and hitting it with a hammer. He knew the rock would break so he wondered what might happen if you took one of the broken pieces and hit that and so on. He arrived at the conclusion that you would eventually be left with a piece that was so small it could not be broken any more.

But that was as far as it went. The Greek philosophers did no experiments and believed everything to be made of earth, fire, air and water. These ideas were hard to get rid of and there are even people today who believe that the Greek ideas are correct! Gradually, science progressed and by the end of the 18th Century, scientists were coming up with ideas about the atom.

Early atomic models explained how many chemicals behaved, but there were times when it didn't work. It was these imperfections of the theory that lead to new work and new ideas. Eventually the realisation came late in the 19th century - an atom could in fact be divided up into smaller particles - protons (with a positive charge), neutrons (with a neutral charge) and electrons (with a negative charge). We now see the structure of atoms as being a very complex arrangement of protons, neutrons and electrons - but mainly empty space.

Here are 10 questions on atomic structure to help ensure your understanding is spot on.

1.
Pick the correct combination for the charges of sub-atomic particles.
Proton +ve Neutron 0 Electron -ve
Proton 0 Neutron +ve Electron -ve
Proton +ve Neutron -ve Electron 0
Proton 0 Neutron 0 Electron -ve
The protons attract and keep the electrons in the atom as these two particles have opposite charges
2.
The numbers in the options below represent the masses of the three sub-atomic particles. Pick the correct combination.
Proton 1 Neutron 0 Electron 1
Proton 0 Neutron 1 Electron 1
Proton 1 Neutron 1 Electron 0
Proton 1 Neutron 1 Electron 1
The mass of an electron is actually about 1/1860 amu, but since this is such a tiny mass, it is referred to as being 0
3.
The mass number of an element tells us...
the number of protons in the nucleus
the number of protons plus electrons
the number of neutrons plus electrons
the number of neutrons plus protons
It is the total number of protons and neutrons found in the nucleus
4.
The atomic number of an element tells us...
the number of neutrons in the nucleus
the number of electrons orbiting the nucleus
the number of protons orbiting the nucleus
the number of electrons in the nucleus
The answer mentioning neutrons is incorrect because you need the mass number as well as the atomic number to work this out. Two of the other answers are incorrect because protons don't orbit the nucleus and you don't find electrons in the nucleus.

The atomic number is also called the proton number because it tells you the number of protons in the nucleus. For the GCSE, you need to know that elements are neutral atoms. In a neutral atom, the number of electrons orbiting the nucleus is the same as the number of protons within the nucleus. If you are not sure why, ask your science teacher to explain

5.
The atomic number of an element is 11 and its mass number is 23. Pick the correct combination of protons, neutrons and electrons.
p=12, n=12, e=11
p=11, n=11, e=12
p=12, n=11, e=11
p=11, n=12, e=11
The number of protons and the number of electrons are both given by the atomic number i.e. 11 of each. The difference between the atomic number and the mass number gives you the number of neutrons
6.
The protons of an atom are found...
in the nucleus of the atom
in orbit around the outside of the nucleus
dotted throughout the atom
in lines radiating out from the nucleus
They are clustered together with the neutrons
7.
The electrons are found...
in the nucleus of the atom
in orbit around the outside of the nucleus
dotted throughout the atom
in lines radiating out from the nucleus
They are found in specific areas known as energy levels or electron shells
8.
The neutrons of an atom are found...
in the nucleus of the atom
in orbit around the outside of the nucleus
dotted throughout the atom
in lines radiating out from the nucleus
They are clustered together with the protons
9.
Carbon has two isotopes. These atoms have...
The same number of protons, but different numbers of electrons
The same number of electrons, but different numbers of protons
The same number of protons, but different numbers of neutrons
The same number of neutrons, but different numbers of electrons

The mass number shown in the Periodic Table is an average of the mass of the isotopes

10.
If an element has 56 protons, 56 electrons and 81 neutrons, what is its mass number?
56
81
137
112
Mass number = number of protons + number of neutrons