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Question 1
All the different substances that make up the universe are made from chemical elements. |
a) | What is an element?
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b) | The Earth’s atmosphere today contains nitrogen, oxygen, argon, carbon dioxide and other gases. |
Draw one line from each substance to the correct description of the substance.
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c) | Many substances are compounds. What is a compound?
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Question 2
Balanced symbol equations with state symbols are used to describe chemical reactions. |
a) | The symbol equation below shows the chemical reaction that occurs between solutions of lead nitrate and potassium chloride. Balance the symbol equation below. Pb(NO3)2 (aq) + KCl (aq) âž” KNO3 (aq) + PbCl2 (s) 2 2
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b) | The equation tells you the formulae of the two products of the reaction. What are the names of the two products?
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c) | State other information about the products that is provided by the equation.
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d) | Explain why an unbalanced chemical equation cannot correctly represent a reaction.
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Question 3
The image below shows three elements: hydrogen, oxygen, and aluminium, as they are represented in the periodic table. |
a) | State the atomic number of oxygen.
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b) | State the relative atomic mass of aluminium.
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c) | Draw the electron configuration of aluminium.
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d) | Balance the following chemical equations involving the three elements in the image above. H2 + O2 âž” H2O Al + O2 âž” Al2O3 2 2 4 3 2
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Question 4
Oxygen is an element with three naturally occurring isotopes. |
a) | Give the meaning of the term 'isotopes’. Answer in terms of subatomic particles.
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b) | The table below shows the mass numbers and percentage abundances of the isotopes of oxygen. |
Use the isotopic abundances data given in the table to calculate the relative atomic mass (Ar) of oxygen. Give your answer to 1 decimal place.
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c) | Oxygen is in group 6 of the periodic table. State the number of outer shell electrons in an oxygen atom.
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d) | Draw the electron configuration of an atom of oxygen.
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e) | What is the formula of an oxygen ion? A O+ B O2+ C O- D O2-
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Question 5
There are eight elements in the third row of the periodic table, from sodium to argon. |
a) | The image below shows an atom with three energy levels. Complete the image to show the electronic structure of a sodium atom.
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b) | What does the central part of the atom, labelled A, represent in the image?
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c) | Name the subatomic particles in part A of the sodium atom. Give the relative charges and masses of these subatomic particles.
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d) | Describe the structure of an argon atom.
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Question 6
Models of the atom have gone through many changes over time, evolving to fit new experimental data. |
a) | Atoms were first thought to be tiny spheres that could not be divided. J. J. Thomson discovered a particle that led to the plum pudding model of the atom. Which particle did J. J. Thomson discover?
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b) | Draw a diagram showing the plum pudding model of the atom.
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c) | Ernest Rutherford fired particles at gold atoms. Some of these particles were scattered. The results led to the nuclear model of the atom. Which type of particle was fired at the gold atoms?
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d) | The plum pudding model did not have a nucleus. Describe three other differences between the nuclear model of the atom and the plum pudding model.
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e) | Which scientist first suggested that electrons orbit the nucleus at specific distances? A Bohr B Dalton C Chadwick D Mendeleev
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Question 7
Carbon has three isotopes, carbon-12, carbon-13 and carbon-14. The different isotopes have different mass numbers. |
a) | Define mass number.
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b) | Why is the mass number different in the three isotopes of carbon?
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c) | The diagram below represents a carbon atom. Name subatomic particles A, B and C.
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d) | Which of the carbon isotopes is shown in the diagram above? Explain your answer.
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e) | Which of the following terms correctly describes carbon? A compound B mixture C alloy D element
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Question 8
The plum pudding model was an earlier model of the atom. It suggested that the atom was a ball of positive charge with electrons embedded in it. |
a) | Evidence from the alpha particle scattering experiment led to a change in the model of the atom from the plum pudding model to the nuclear model. Explain how.
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b) | Niels Bohr adapted the nuclear model. Describe the change that Bohr made to the nuclear model.
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c) | Draw a carbon atom according to Bohr's model of the atom. Model answer
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Question 9
The diagram below represents a nitrogen atom. |
a) | Complete the table to show the name of each particle and the charge of each particle in the nitrogen atom.
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b) | Why is there no overall electrical charge on each atom?
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c) | Where in the atom are the protons and neutrons located?
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d) | Complete the following sentences. The atomic number of nitrogen is . This is the same as the number of in the nucleus of the nitrogen atom. The sum of the protons and neutrons in a nitrogen atom is its number, 14. 7 protons mass
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Question 10
Gallium has two isotopes. Their mass numbers are 69 and 71. The percentage abundance of each isotope is:
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a) | Calculate the relative atomic mass of gallium.
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b) | Complete the table with information for the two isotopes of gallium.
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c) | Use the information from the table above to explain why 69Ga and 71Ga are isotopes of gallium.
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d) | Complete the sentences below. In a gallium atom, the particles with a negative charge are called . Particles in the nucleus with no charge are called . A gallium atom has no overall charge because is has the same number of electrons and . electrons neutrons protons
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Question 11
In each flask are particles of four different gases. Each circle represents an atom. |
a) | State which of the diagrams, from A to D, represents:
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b) | Two of the gases in flasks A to D are elements, and two of the gases are compounds. Identify which gases are elements and which gases are compounds, and explain your answer.
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Question 12
This question is about elements, compounds and mixtures. |
a) | What is an element?
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b) | Which two of the following substances are elements? A aluminium B air C pure water D oxygen E milk F sodium chloride
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c) | What is a compound?
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d) | Which two of the following substances are compounds? A aluminium B air C pure water D oxygen E milk F sodium chloride
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