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Aluminium has 3 electron shells with 3 electrons in the outer shell.

# Atomic Structure 2

Students of GCSE Chemistry will be expected to know the atomic structure of certain elements in the Periodic Table. They should know the numbers and arrangement of protons, neutrons and electrons as well as their atomic numbers and their atomic mass. This is the second in our series of three GCSE Chemistry quizzes on atomic structure and it helps to familiarise students with these elements.

Towards the end of the 18th Century, the scientist John Dalton introduced his theory of atoms to the scientific community. He was trying to help science make sense of the world by bringing his ideas of the atom to the centre of scientific theory. His ideas were not new but science was becoming more popular than before and so ideas like this were more likely to be noticed, discussed, modified and accepted more widely than in the past.

Dalton used small wooden balls and sticks to explain his theory. It took many years for the theory to become accepted - 'Atoms are round bits of wood invented by Mr Dalton' wrote a critic of John Dalton on reading his theory of 'atomism'. Dalton's theory had four parts; first that chemical elements are made of atoms, secondly and thirdly, that atoms of an element are identical to each other, but different from those of different elements. The new science here was that Dalton was able to work out the weight or mass of these atoms. The final part of his theory was that atoms combine in whole number ratios. Although it had taken some time for Dalton's theory to be accepted, it is now the basis for all chemical calculations. The models of atoms that you have seen, and possibly used in lessons, are not much different to those of Dalton's models.

One of the things that Dalton believed was that the atoms of an element were identical to each other. Something that seems obvious to you, but was revolutionary at the time. We now understand why this is the case and can include the number of protons in the definition of an element as follows - atoms that have the same number of protons are the same element. So it doesn't matter about how many electrons or neutrons there are, atoms of the same element always contain the same number of protons. Where two atoms exist that have the same number of protons but different numbers of neutrons, we say that they are isotopes. Isotopes are forms of the same element with a different atomic mass, one example being a radioactive form of an element.

Now try these question about atomic structure - you will find it helpful to have your copy of the Periodic Table handy.

1.
Chlorine has two isotopes, one with atomic mass 35 and one with atomic mass 37. Pick the correct combination of subatomic particles for the two isotopes.
Cl 35 - 17 Protons; 17 Neutrons; 18 Electrons
Cl 37 - 20 Protons; 17 Neutrons; 17 Electrons
Cl 35 - 17 Protons; 18 Neutrons; 17 Electrons
Cl 37 - 17 Protons; 20 Neutrons; 17 Electrons
Cl 35 - 18 Protons; 18 Neutrons; 17 Electrons
Cl 37 - 17 Protons; 18 Neutrons; 20 Electrons
Cl 35 - 17 Protons; 17 Neutrons; 18 Electrons
Cl 37 - 17 Protons; 20 Neutrons; 20 Electrons
Isotopes have the same number of protons and electrons, but a different number of neutrons
2.
Pick the name for the element with 6 electrons.
Carbon
C
Boron
Nitrogen
Make sure you give the name when you are asked for the name
3.
There are two elements that are liquid at room temperature. They are...
chlorine and mercury
bromine and chlorine
mercury and bromine
mercury and phosphorus
This property cannot be predicted using atomic structure
4.
Pick the correct symbol for the element with the mass number 84.
Bromine
Ar
Kr
Krypton
Make sure that when you are asked for the symbol, you give the symbol and NOT the name
5.
An element has 3 electron shells with 3 electrons in the outer shell. Which element is it?
Oxygen
Aluminium
Boron
Chlorine
Aluminium has the atomic number of 13 so it has 2 electrons in the first energy level (shell), 8 in the second leaving 3 in the outermost
6.
An element has 2 electron shells with 6 electrons in its outer shell. Which element is it?
Oxygen
Aluminium
Boron
Chlorine
Oxygen has an atomic number of 8
7.
An element has 45 electrons around its nucleus. The element is...
rhodium
ruthenium
osmium
iridium
Atomic number = 45 = number of protons = number of electrons
8.
Name the element that contains 12 protons, 12 electrons and 12 neutrons.
Sodium
Magnesium
Potassium
Aluminium
Atomic number of magnesium is 12, mass number 24
9.
If the temperature is increased to 100°C, which element does NOT become a liquid?
Potassium
Gallium
Phosphorus
Lithium
The melting point of Lithium is 180°C
10.
Pick the symbol pairs for elements that do NOT have the same number of neutrons in their nuclei.
K and Ca
Na and Mg
F and Ne
Li and Be
Li has 4 neutrons and Be has 5 neutrons