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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
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 7
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 8
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 9
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 10
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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