AS LEVEL CHEMISTRY

1.1.1 ATOMS 1.2.1 ELECTRON STRUCTURE 1.3.1 PERIODICITY

ASSESSED HOMEWORK

Answer all questions Max 61 marks

Name

..

Mark

../61

....%

Grade

1

1.

The Group 7 element bromine was discovered by Balard in 1826. Bromine gets its name from the Greek bromos meaning stench. Bromine consists of a mixture of two isotopes, (i) What is meant by the term isotopes? ......................................................................................................................... .........................................................................................................................[1]79

Br and

81

Br.

(ii)

Complete the table below to show the atomic structures of the bromine isotopes. protons79 81

neutrons

electrons

Br Br[2]

(iii)

Write the full electronic configuration of a bromine atom. 1s .................................................................[1] [Total 4 marks]2

2.

Metal A can be identified from its relative atomic mass. Analysis of a fifty pence coin showed that two isotopes of metal A were present with the following percentage abundances. isotope relative isotopic mass % abundance (i) isotope 1 63.0 77.2 isotope 2 65.0 22.8

Define the term relative atomic mass. ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... .........................................................................................................................[3]

(ii)

Calculate the relative atomic mass of the sample of metal A. Give your answer to three significant figures. answer ...........................[2]

(iii)

Use your answer to (iii) and the Data Sheet to suggest the identify of metal A. .........................................................................................................................[1] [Total 6 marks]

3.

The element titanium, Ti, atomic number 22, is a metal that is used in the aerospace industry for both airframes and engines. A sample of titanium for aircraft construction was analysed using a mass spectrometer 46 47 48 and was found to contain three isotopes, Ti, Ti and Ti. The results of the analysis are shown in the table below. isotope relative isotopic mass percentage composition (a) (i)46

Ti

47

Ti

48

Ti

46.00 8.9

47.00 9.8

48.00 81.3

Explain the term isotopes.

................................................................................................................ ................................................................................................................[1]

(ii)

Complete the table below for atoms of two of the titanium isotopes. isotope46 47

protons

neutrons

electrons

Ti Ti[2]

(b)

Using the information in the first table, calculate the relative atomic mass of this sample of titanium. Give your answer to three significant figures.[2] [Total 5 marks]

3

4.

A sample of carbon was found to contain 95% of (i)13

12

C and 5% of

13

C.

The C isotope has a relative isotopic mass of 13.00. Define the term relative isotopic mass. ......................................................................................................................... ......................................................................................................................... .........................................................................................................................[2]

(ii)

Calculate the relative atomic mass of this sample of carbon to three significant figures. Ar = ............................................[2] [Total 4 marks]

5.

Magnesium exists naturally as a mixture of its isotopes,

24

Mg,

25

Mg and

26

Mg.

The isotopes in magnesium can be separated by mass spectrometry. The diagram below shows a mass spectrometer. (i) Complete the table below to show the composition of the isotopes. protons25 26 25

Mg and

26

Mg

neutrons

electrons

Mg Mg[2]

(ii)

Complete the electronic configuration of an atom of2

24

Mg.

1s ....................................................................................................................[1]

(iii) Results from the mass spectrum of a sample of magnesium are shown below. isotope relative isotopic mass % abundance24

Mg

25

Mg

26

Mg

24.00 78.60

25.00 10.11

26.00 11.29

Calculate the relative atomic mass of the sample of magnesium. Give your answer to two decimal places. answer ...............................[2] [Total 5 marks]

6.

The diagram below shows the variation in the first ionisation energies of elements across Period 2 of the Periodic Table.2 2 5 0 5 0 5 0 0 0 0 L 0 0 0 3 0 0 0 0 i B e B C N O F N e

fir s t io n is a tio n 1 e n e rg y / k J m o l 1 1

4 a t o m i c

5 n u m b e r

6

(i)

Define the term first ionisation energy. ......................................................................................................................... ......................................................................................................................... .........................................................................................................................[3]

(ii)

Explain why the first ionisation energies show a general increase across Period 2. ......................................................................................................................... ......................................................................................................................... .........................................................................................................................[2]

5

(iii)

Explain why the first ionisation energy of B is less than that of Be. ......................................................................................................................... ......................................................................................................................... .........................................................................................................................[2] [Total 7 marks]

7.

Antimony, Sb, is a metal used in alloys to make lead harder. Bullets contain about 1% of antimony for this reason. Antimony has two main isotopes. (i) What do you understand by the term isotopes? ......................................................................................................................... .........................................................................................................................[1]

(ii)

Complete the table below to show the properties of particles that make up isotopes. proton relative mass relative charge[2] [Total 3 marks]

neutron

electron

8.

In their reactions, calcium and strontium each lose electrons to form ions with a 2+ charge. The first and second ionisation energies of calcium and strontium are shown below. 1st ionisation energy 1 / kJ mol calcium strontium (i) 590 550 2nd ionisation energy 1 / kJ mol 1145 1064

Write an equation, with state symbols, to represent the second ionisation energy of calcium. .........................................................................................................................[2]

(ii)

Why are the second ionisation energies of calcium and strontium greater than their first ionisation energies? ......................................................................................................................... ......................................................................................................................... .........................................................................................................................[1]

(iii)

Explain why the first and second ionisation energies of strontium are less than those of calcium. ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... .........................................................................................................................[3] [Total 6 marks]

7

9.

Electrons are arranged in energy levels. (a) An orbital is a region in which an electron may be found. Draw diagrams to show the shape of an s orbital and of a p orbital.

s orbital

p orbital[2]

(b)

Complete the table below to show how many electrons completely fill each of the following. number of electrons a d orbital a p sub-shell the third shell (n = 3)[3]

(c)

The energy diagram below is for the eight electrons in an oxygen atom. The diagram is incomplete as it only shows the two electrons in the 1s level.

e

n

e

r g

y

1

s

Complete the diagram for the oxygen atom by: (i) adding labels for the other sub-shell levels,[1]

(ii)

adding arrows to show how the other electrons are arranged.[1] [Total 7 marks]

10.

Successive ionisation energies provide evidence for the arrangement of electrons in atoms. The table below shows the eight successive ionisation energies of oxygen. ionisation number ionisation 1 energy / kJ mol (i) 1st 1 314 2nd 3 388 3rd 5 301 4th 7 469 5th 10 989 6th 13 327 7th 71 337 8th 84 080

Define the term first ionisation energy. ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... .........................................................................................................................[3]

(ii)

Write an equation, with state symbols, to represent the third ionisation energy of oxygen. .........................................................................................................................[2]

(iii)

Explain how the information in the table above provides evidence for two electron shells in oxygen. ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... .........................................................................................................................[2] [Total 7 marks]

11.

Relative atomic mass, Ar, can be used to compare the masses of atoms of different elements. (i) Explain what you understand by the term relative atomic mass. ......................................................................................................................... ......................................................................................................................... .........................................................................................................................[3]

9

(ii)

The antimony in a bullet was analysed by a forensic scientist to help solve a crime. The antimony was found to have the following percentage composition by 121 123 mass: Sb, 57.21%; Sb, 42.79%. Calculate a value for the relative atomic mass of the antimony. Give your answer to 4 significant figures. Ar ...................................[2] [Total 5 marks]

12.

Carbon is in the p-block of the Periodic Table. Naturally occurring carbon contains a 12 13 mixture of two isotopes, C and C. Complete the table below for the atomic structure of the isotopes isotope12 13 12

C and

13

C.

protons

neutrons

electrons

C C[Total 2 marks]