C1 – Higher – Topic 1 – Key concepts – Atomic Structure

Q1.

(a) The table shows the number of electrons, neutrons and protons in particles P, Q, R, S, T and V.

(i) Which particle is a negatively charged ion?

Put a cross ( ) in the box next to your answer. (1)

A P B S C T D V

(ii) Which particles are atoms of metals? Put a cross ( ) in the box next to your answer.

(1) A P and R B Q and R C Q and S D Q, S and V (b) Each element has an atomic number.

(i) State what is meant by atomic number. (1)

.............................................................................................................................................. .............................................................................................................................................. (ii) The atomic number of boron is 5. Boron exists as two isotopes boron-10 and boron-11.

Use this information to explain why boron-10 and boron-11 are isotopes. (2)

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(c) (i) Explain what is meant by the term relative atomic mass. (2)

.............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. (ii) A sample of boron contains 19.7% of boron-10. 80.3% of boron-11. Use this information to calculate the relative atomic mass of boron.

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(Total for Question = 10 marks) Q2.

(a) Complete the sentence by putting a cross ( ) in the box next to your answer. The particles in atoms are electrons, neutrons and protons. The mass of an electron is

(1) A greater than the mass of a neutron B the same as the mass of a proton C smaller than the mass of a proton D the same as the mass of a neutron (b) The atomic number of oxygen is 8.

The mass number of an atom of oxygen is 17. Describe the number and type of particles in the nucleus of this atom.

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(c) Sulfur and oxygen are both in group 6 of the periodic table. Explain, in terms of their electronic configurations, why they are both in group 6.

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(d) An atom of phosphorus contains 15 electrons. Describe how these 15 electrons are arranged in a phosphorus atom.

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(e) Phosphorus oxide is a compound that contains covalent bonds. (i) Describe what is meant by a covalent bond.

(2) .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. (ii) The formula of a molecule of phosphorus oxide is P4O10

Give the empirical formula of this oxide. (1)

.............................................................................................................................................. (Total for Question = 10 marks)

Q3. The elements beryllium, magnesium, calcium, strontium and barium are in group 2 of the periodic table.

There are three common isotopes of magnesium.

(i) These isotopes are shown in Figure 6.

Complete Figure 6 to show the number of protons and neutrons in an atom of each of the other two isotopes.

(2)

Figure 6

(ii) A sample of magnesium contains 78.60% magnesium-24, 10.11% magnesium-25 and 11.29% magnesium-26.

Use this information to calculate the relative atomic mass of magnesium in this sample. Give your answer to 3 significant figures.

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relative atomic mass = ........................................................... (Total for question = 6 marks)

Q4. Each element has an atomic number. (i) State what is meant by atomic number.

(1) .............................................................................................................................................. .............................................................................................................................................. (ii) The atomic number of boron is 5. Boron exists as two isotopes boron-10 and boron-11.

Use this information to explain why boron-10 and boron-11 are isotopes. (2)

.............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. Q5. The atomic number of magnesium is 12.

Magnesium exists as three isotopes: magnesium-24, magnesium-25 and magnesium-26. Describe, by referring to the numbers of subatomic particles, the differences between one atom of each of these isotopes.

(2) .............................................................................................................................................

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Q6. (i) Explain what is meant by the term relative atomic mass.

(2) .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. (ii) A sample of boron contains 19.7% of boron-10. 80.3% of boron-11. Use this information to calculate the relative atomic mass of boron.

(3) .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. Q7. A carbon atom contains 6 electrons, 7 neutrons and 6 protons.

(i) State the mass number of this carbon atom. (1)

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(ii) Give the electronic configuration of this carbon atom. (1)

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Q8.

* A sample of magnesium contains

79% of magnesium-24 atoms 10% of magnesium-25 atoms 11% of magnesium-26 atoms.

In most calculations the relative atomic mass of magnesium used is 24.

Use this information to explain why, in this sample, magnesium has a relative atomic mass of 24.3. (6)

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Q9.

Particles and formulae

(a) Atoms contain protons, neutrons and electrons. Complete the table to show the relative mass and relative charge of each particle and its position in an atom.

(3)

(b) Complete the sentence by putting a cross ( ) in the box next to your answer.

An atom of an element always contains (1)

A more protons than neutrons

B equal numbers of protons and neutrons

C more electrons than protons

D equal numbers of protons and electrons

(c) The symbols for some atoms are given in the box

From the box, choose the symbol of (i) an atom in group 2 of the periodic table

(1)

........................................................... (ii) an atom that readily forms an ion with a charge of 2−

(1)

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(d) The formula of aluminium nitrate is Al(NO3)3

(i) State the total number of atoms in the formula Al(NO3)3

(1)

........................................................... (ii) What is the most likely formula of aluminium nitride?

Put a cross ( ) in the box next to your answer. (1)

A Al(NO3)2 B AlNO3 C AlNO2 D AlN

(Total for question = 8 marks)

Q10. Chlorine and carbon

(a) Chlorine has an atomic number of 17. Chlorine-35 and chlorine-37 are two isotopes of chlorine.

(i) Complete the table to show the numbers of protons, neutrons and electrons in each of the isotopes.

(2)

(ii) A normal sample of chlorine contains only chlorine-35 and chlorine-37 atoms.

Explain why the relative atomic mass of chlorine is 35.5 (2)

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(b) Tetrachloromethane is a simple molecular, covalent compound. The formula of its molecule is CCl4.

There are four electrons in the outer shell of a carbon atom. There are seven electrons in the outer shell of a chlorine atom. Draw a dot and cross diagram to show the bonding in a molecule of tetrachloromethane, CCl4. Show outer shell electrons only.

(2) *(c) The diagrams show the arrangements of carbon atoms in diamond and in graphite.

Compare a use of diamond with a use of graphite, explaining each use in terms of the bonding and structure. In your answer you should use information from the diagrams.

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............................................................................................................................................. (Total for question = 12 marks)

Mark Scheme Q1.

Answer Acceptable answers

Mark

(a)(i) C T (1) (a)(ii) C Q and S (1) (b)(i) number of protons

(in nucleus of atom) ignore number of electrons eg number of protons and electrons worth (1)

(1)

(b)(ii) An explanation including • (atoms of) both contain 5 /same number of protons/same atomic number (1) • boron-10 atoms contain 5 neutrons but boron-11 atoms contain 6 neutrons / different numbers of neutrons/ different mass number (1)

ignore electrons boron-11 atoms contain 1 more neutron / boron-10 atoms contain 1 less neutron

(2) (c)(i) An explanation

including the following • M1 average/mean mass (of atoms of an element) (1) • M2 compared to 1/12 mass carbon-12 (atom)/ (mass of) carbon-12 (atom) taken as 12 (1)

For M1 reject weight reject if mass of molecule reject if mass of neutrons and protons any reference to carbon-12 scores mark

(2) (c)(ii) [19.7 × 10] (1) +[80.3

× 11] (1) /100 (1) (=10.8) [0.197 ×10] (1) + [0.803 ×11] (1) = [1.97 + 8.83] (1) (=10.8)

If no working shown 10.8(03) worth 3 marks

(3) Q2.

Answer Acceptable answers

Mark

(a) C smaller than the mass of a proton

(1)

(b)

An description linking • 8 protons (1) • (and) 17-8/9 neutrons (1)

ignore references to electrons in shells / charges on particles if electrons in nucleus max 1 protons and neutrons with incorrect numbers (1) (2)

(c) Explanation linking • (both have) same number (of electrons) in outer shell(1) • 6 (electrons in outer shell) (consequent on first point) (1)

correct electronic configurations or diagrams alone max 1 'they both have 6 in the outer shell' scores both marks allow 'both need 2 (more) (electrons) to fill outer shell' for both marks (2)

(d) A description to include • 2.8 (in 1st and 2nd shell)(1) • 5 (in outer shell)(1)

suitable diagram in place of 2.8(1).5(1) electrons in shells / orbits / rings(1)

(2) (e)(i) A description to

include • electron(s) shared (1) • pair(s) of / two (electrons) (1)

can be shown in a diagram of a covalent bond any mention of ions scores zero

(2) (e)(ii) P2O5 Reject P2O5 / P2O5 (1)

Q3.

Q4.

Answer Acceptable answers

Mark

(i) number of protons (in nucleus of atom)

ignore number of electrons eg number of protons and electrons worth (1)

(1)

(ii) An explanation including • (atoms of) both contain 5 /same number of protons/same atomic number (1) • boron-10 atoms contain 5 neutrons but boron-11 atoms contain 6 neutrons / different numbers of neutrons/ different mass number (1)

ignore electrons boron-11 atoms contain 1 more neutron / boron-10 atoms contain 1 less neutron

(2) Q5.

Q6.

Answer Acceptable answers

Mark

(i) An explanation including the following • M1 average/mean mass (of atoms of an element) (1) • M2 compared to 1/12 mass carbon-12 (atom)/ (mass of) carbon-12 (atom) taken as 12 (1)

For M1 reject weight reject if mass of molecule reject if mass of neutrons and protons any reference to carbon-12 scores mark

(2) (ii) [19.7 × 10] (1) +[80.3

× 11] (1) /100 (1) (=10.8) [0.197 ×10] (1) + [0.803 ×11] (1) = [1.97 + 8.83] (1) (=10.8)

If no working shown 10.8(03) worth 3 marks

(3) Q7.

Q8.

Q9.

Q10.