Atomic Structure
6 marks · NormalThis question is about atoms, molecules, and the structure of the atom.
State what is meant by each of the following terms:
atom
molecule
The diagram below represents a simple atom.
Name the three types of sub-atomic particles found in atoms and state the position of each.
The atomic number of lithium is 3, and its mass number is 7.
Calculate the number of each type of sub-atomic particle in one atom of lithium.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a(i)) The smallest particle of an element that can still be recognised as that element.
(a(ii)) A group of two or more atoms chemically bonded together.
(b) Proton – found in the nucleus; Neutron – found in the nucleus; Electron – found outside the nucleus (in shells or energy levels). · must show proton, nucleus, neutron, electron, shell, outside nucleus
(c) Number of protons = 3; number of neutrons = 4; number of electrons = 3.
Common mistakes: Confusing the total number of protons and neutrons; Misidentifying the electron position
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Marking points
B1 (a(i)) · 1 mark · Correct definition of atom.
B1 (a(ii)) · 1 mark · Correct definition of molecule.
B1 (b) · 1 mark · Identifies proton and its position (nucleus).
B2 (b) · 1 mark · Identifies neutron and its position (nucleus).
B3 (b) · 1 mark · Identifies electron and its position (outside nucleus/in shells).
B1 (c) · 1 mark · Correct numbers for protons, neutrons, and electrons in lithium (3, 4, 3).
Worked solution
a(i) An atom is the smallest piece of an element that can still be recognised as that element.
a(ii) A molecule is a group of two or more atoms chemically bonded together.
b Protons and neutrons are found in the nucleus of the atom. Electrons are found outside the nucleus, in shells (or energy levels) surrounding the nucleus.
c Lithium (atomic number 3, mass number 7):