Nuclear Atoms Structure, specific charge, isotopes, nuclear decay
83 minutes 81 marks
Page 1 of 16
Q1.
(a) The nucleus of a particular atom has a nucleon number of 14 and a proton number of 6. (i)
State what is meant by nucleon number and proton number. nucleon number .................................................................................... ............................................................................................................... ............................................................................................................... proton number ...................................................................................... ............................................................................................................... ............................................................................................................... (1)
(ii)
Calculate the number of neutrons in the nucleus of this atom.
answer = ..................................... (1)
(iii)
Calculate the specific charge of the nucleus.
answer = .......................... Ckg–1 (3)
(b)
The specific charge of the nucleus of another isotope of the element is 4.8 × 107 Ckg–1. (i)
State what is meant by an isotope. ............................................................................................................... ............................................................................................................... ............................................................................................................... (2)
(ii)
Calculate the number of neutrons in this isotope.
answer = ..................................... (3) (Total 10 marks)
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Q2.
(a) How many protons, neutrons and electrons are there in an atom of caesium, which is the most abundant and stable isotope of caesium.
,
......................... protons ......................... neutrons ......................... electrons (2)
(b)
(i)
Explain what is meant by isotopes. ............................................................................................................. .............................................................................................................
(ii)
Write down an isotope
that is likely to be a beta minus emitter.
............................................................................................................. (3)
(c)
Determine the specific charge of a nucleus of
.
specific charge = .......................... (3) (Total 8 marks)
Q3.
(a)
A stable atom contains 28 nucleons.
Write down a possible number of protons, neutrons and electrons contained in the atom. ....................................... protons ...................................... neutrons ...................................... electrons (2)
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(b)
An unstable isotope of uranium may split into a caesium nucleus, a rubidium nucleus and four neutrons in the following process.
(i)
Explain what is meant by isotopes. ............................................................................................................. ............................................................................................................. .............................................................................................................
(ii)
How many neutrons are there in the
nucleus?
............................................................................................................. (iii)
Calculate the ratio
, in C kg–1, for the
nucleus.
............................................................................................................. ............................................................................................................. ............................................................................................................. (iv)
Determine the value of X for the rubidium nucleus. ............................................................................................................. X = .................................... (6) (Total 8 marks)
Q4.
(a) State what is meant by the specific charge of a nucleus and give an appropriate unit for this quantity. ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ unit: ................................................... (2)
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(b)
Nucleus X has the same nucleon number as nucleus Y. The specific charge of X is 1.25 times greater than that of Y. (i)
Explain, in terms of protons and neutrons, why the specific charge of X is greater than that of Y. ............................................................................................................... ............................................................................................................... ............................................................................................................... ............................................................................................................... (2)
(ii)
Nucleus X is nucleus Y.
. Deduce the number of protons and the number of neutrons in
number of protons ........................... number of neutrons .......................... (4) (Total 8 marks)
Q5.
(a)
What are isotopes?
...................................................................................................................... ...................................................................................................................... ...................................................................................................................... ...................................................................................................................... ...................................................................................................................... (2)
(b)
One of the isotopes of nitrogen may be represented by (i)
N.
State the number of each type of particle in its nucleus. ............................................................................................................. .............................................................................................................
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(ii)
Determine the ratio
, in C kg–1, of its nucleus.
............................................................................................................. ............................................................................................................. ............................................................................................................. ............................................................................................................. (4)
(c)
(i)
What is the charge, in C, of an atom of removed?
N from which a single electron has been
............................................................................................................. (ii)
What name is used to describe an atom from which an electron has been removed? ............................................................................................................. (2) (Total 8 marks)
A neutral atom of a radium isotope may be represented by
Q6. (a)
(i)
.
Name the constituents of this atom and state how many of each are present. ............................................................................................................. ............................................................................................................. ............................................................................................................. (3)
(ii)
Which constituent of an atom has the largest specific charge? ............................................................................................................. (1)
(iii)
This isotope of radium decays by β– decay to form an element with symbol, Ac. Write down an equation that represents this decay.
(4)
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(b)
is a neutral atom of a different isotope of radium. State a possible value for A and for Z. A: .................................................................................................................. Z: .................................................................................................................. (2) (Total 10 marks)
Q7.
A radioactive isotope of carbon is represented by (a)
C.
Using the same notation, give the isotope of carbon that has two fewer neutrons. ...................................................................................................................... (1)
(b)
Calculate the charge on the ion formed when two electrons are removed from an atom of
C.
...................................................................................................................... ...................................................................................................................... ...................................................................................................................... (2)
(c)
Calculate the value of
for the nucleus of an atom of
C.
...................................................................................................................... ...................................................................................................................... ...................................................................................................................... (2) (Total 5 marks)
Q8.
(a)
How many protons, neutrons and electrons are there in an atom of
?
....................................... protons ....................................... neutrons ....................................... electrons (2)
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(b)
The
atom loses two electrons.
For the ion formed; (i)
calculate its charge in C, .............................................................................................................
(ii)
state the number of nucleons it contains, .............................................................................................................
(iii)
calculate the ratio
in C kg–1.
............................................................................................................. ............................................................................................................. ............................................................................................................. ............................................................................................................. (4) (Total 6 marks)
Q9.
Alpha decay is a process by which an unstable isotope of an element may decay. (i)
State what is meant by isotopes. ...................................................................................................................... ...................................................................................................................... ...................................................................................................................... ...................................................................................................................... (2)
(ii)
Complete this equation for alpha decay.
(2)
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(iii)
Calculate the specific charge of an alpha particle, stating an appropriate unit.
answer = ..................................... (4)
(iv)
Explain why the alpha particle, once outside the nucleus, is unaffected by the strong nuclear force. ...................................................................................................................... ...................................................................................................................... ...................................................................................................................... ...................................................................................................................... ...................................................................................................................... (2) (Total 10 marks)
Q10.
, can decay by emitting a β– particle.
(a)
An unstable nucleus,
(i)
What part of the atom is the same as a β– particle? ............................................................................................................. (1)
(ii)
State the changes, if any, in A and Z when X decays. change in A ......................................................................................... change in Z .......................................................................................... (2)
(b)
In the process of β– decay an anti-neutrino is also released. (i)
Give an equation for this decay. ............................................................................................................. (1)
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(ii)
State and explain which conservation law may be used to show that it is an anti-neutrino rather than a neutrino that is released. ............................................................................................................. ............................................................................................................. ............................................................................................................. ............................................................................................................. (2)
(iii)
What must be done to validate the predictions of an unconfirmed scientific theory? ............................................................................................................. ............................................................................................................. ............................................................................................................. ............................................................................................................. ............................................................................................................. (2) (Total 8 marks)
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M1.
(a)
(i) nucleon number is the number of protons and neutrons OR mass number proton number is the number of protons OR atomic number 1
(ii)
14 – 6 = 8 1
(iii)
specific charge = 6 × 1.6 × 10–19 /(14 × 1.66 × 10–27
)
specific charge = 4.1 × 107 (C kg–1) 3
(b)
(i)
isotopes are variations of an element that have same proton/atomic number but different nucleon number OR different number of neutrons 2
(ii)
4.8 × 107 = 6 × 1.6 × 10–19
/(A × 1.66 × 10–27)
A = 6 × 1.6 × 10–19/(4.8 × 107 × 1.66 × 10–27) A = 12 Number of neutrons = 12-6 3
[10]
M2.
(a)
55 protons
55 electrons (1) 82 neutrons (1) 2
(b)
(i)
same number of protons (1) different number of neutrons (1)
(ii)
(1) 3
(c)
specific charge (= charge/mass) = 55 × 1.6 × 10–19/137 × 1.67 × 10–27 (1) 3.85 × 107 (1) C kg–1 (1) 3
[8]
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M3.
(a)
number of protons = number of electrons (e.g.14) (1)
number of protons + number of neutrons = 28 (1) 2
(b)
(i)
nuclei with the same number of protons (1) but different number of neutrons/nucleons (1)
(ii)
(137 – 55) = 82 (1)
(iii)
(1) = 3.73 × 107 (C kg–1) (1)
(iv)
X (= 236 – 137 – 4) = 95 (1) 6
[8]
M4.
(a)
the ratio of charge to mass of nucleus
C kg−1 2
(b)
(i)
number of protons and neutrons the same or number of neutrons less or mass the same but more protons therefore greater charge 2
(ii)
answers add up to 10 number of protons = 4 number of neutrons = 10 − 4 = 6 evidence of correct calculation eg 5q = 1.25 × ?q ?=4 4
[8]
M5.
(a) (atoms with) same number of protons/same atomic number (1) different number of neutrons/mass number/ nucleons (1) 2
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(b)
(i)
7 protons (1) 8 neutrons (1)
(ii)
(1) = 4.5 × 107 (C kg–1) (1) (4.47 × 107 (C kg–1)) (allow C.E. for incorrect values in (b) (i)) 4
(c)
(i)
(+) 1.6 × 10–19 (C) (1)
(ii)
positive ion (1) 2
[8]
M6.
(a)
(i)
88 protons (1)
140 neutrons (1) 88 electrons (1) 3
(ii)
electron (1) 1
(iii)
(1)(1)(1)(1) 4
(b)
228 ± 10 (1) 88 (1) 2
[10]
M7.
(a)
(1) 1
(b)
2e (1) = (2 × 1.6 × 10−19) = 3.2 × 10−19 C (1) 2
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(c)
(1) = 4.1(1) × 107 C kg−1 (1) 2
[5]
M8.
(a) 6 (protons) and 6 (electrons) (1) 8 (neutrons) (1) 2
(b)
(i)
(2 × 1.6 × 10–19) = 3.2 × 10–19 (C) (1)
(ii)
14 (1)
(iii)
m = 14 × 1.67 × 10–27 (kg) (1)
= 1.4 × 107 (C kg–1) (1) (1.37 ×107 (C kg–1)) (allow C.E for values from (i) and (ii)) 4
[6]
M9.
(i)
same atomic number/number of protons
different mass/nucleon number/different number of neutrons 2
(ii) 2
(iii)
= 4.8 × 107 Ckg–1 4
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(iv)
strong nuclear force is short range no effect at distances larger 3 fm (except any distance less than 10 fm) 2
[10]
M10.
(a)
(i)
an electron (1) 1
(ii)
change in A = 0 (1) change in Z = +1 (1) 2
(b)
(i)
(1) or n → p + e– + or d → u + e– + 1
(ii)
lepton number must be conserved (1) lepton number before decay equals zero hence after decay lepton number of electrons cancels with lepton number of anti-neutrino or zero on both sides (1) 2
(iii)
hypothesis needs to be tested by experiment (1) experiment must be repeatable (1) or hypothesis rejected 2
[8]
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