Answers for chapter 4: The Periodic Table

1) a) Metal : P/Q/R/S/T Non-metal : V/U/W/X

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b) 2.8.5 1

c) R 1

d) Electronegativity increases from Q to U

1. The atomic size decreases from Q to U 2. The nuclei attraction forces between electrons and nucleus increases

from Q to U

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e) Q+

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f) X

Atom X has achieved stable octet electron arrangement

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g) 2R + U2 → 2RU

h) 1. form coloured ions 2. has more than one oxidation number

3. as catalyst 4. form complex ions

2) a) Group 16, Period 3 1

b) 2D + 2H2O→ 2DOH + H2 1

c) i) G 1

ii) The nuclei attraction towards the valence electrons is weaker in

G. Thus it is easier for G to lose / release an electron to form a positively charged ion.

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d) i) F 1

ii) Has stable/octet electron arrangement

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e) Show coloured ion//formed complex ion//has various oxidation number//act as catalyst

f) G,H, D,E,F,C

3) a) i) Y 1

ii) R

iii) X

b) R, Q, Y, X, T 1

c) 4 1

d) have the same number of shells filled with electrons 1

e) i) T burn rapidly and brightly with a yellow flame/ T release white fumes which become a white solid on cooling to room temperature.

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ii) 2T + Cl2 →2TCl 1

f) Wear safety goggles and gloves. Handle Y in a fume chamber.

4) a) i) transition element 1

ii) formed coloured compound or ions / different oxidation number / form complex ions/act as a catalyst

b) i) Same number of valence electron 1

b) ii) E

b) iii) attraction between the nucleus towards valence electrons is weaker in E.

Thus, it is easier for atom of E to release an electron to form a positively charged ion.

c) i) M 1

c) ii) The increase of the positive charge in M causes the attraction of nucleus become stronger. Electrons are pulled closer to the nucleus in M than D.

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5) a) P 1

b R

c i The electronegativity is increases from Q to V 1

ii The atomic size decreases from Q to V. The attraction force between nucleus and electrons increases from Q to V so electronegativity increases.

d R is more reactive than Q

e Because the element has octet electron arrangement or

Because the outermost shell fill with 8 electrons

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f V has higher proton number than Q. Hence it has stronger nuclei attraction of the electrons.

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g i Q, U, V

ii Across the period, the proton number increasing from Q to V.

Nuclei charge in the nucleus also increasing from Q to V. Force of attraction between the nucleus and electron become more and more stronger from Q to V// Electrons at the outermost shell are pulled closer toward the nuclues in V.

6) a) i Group 13 period 3 1

ii It has 3 valence electrons and 3 shells fill with electrons 2

b i Size of X is smaller than W. 1

ii Number of positive charge in X is more than W.

Electrons in X is pull nearer to the closer.

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c X2 + 2Z 2ZX 1

d i Y.. 1

ii It has achieved stable octet electron arrangement 1

7) a) Na/ Mg/ Al 1

b 2.8

c Force of attraction between nucleus and electrons is stronger in chlorine atom 1

d Semiconductor / to produce microchips / to make concrete/ cement/ ceramic 1

e i Chemically inert / argon atom achived stable octet electron arrangement 1

ii Volume of argon gas = 0.002 x 24 = 0.048 dm3 1

8) a) i) 1.The electron arrangement of atom Q : 2.7 2. The electron arrangement of atom R : 2.4

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ii) 1.The number of neutrons in atom Q is 10 2. Number of electron in atom Q is 9

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b) 1. Q and R form covalent bond. 2.Atom Q has an electron arrangement of 2.7 3. Atom R has an electron arrangement of 2.4

4.To achieve the stable electron arrangement, atom R shares electrons with atom Q.

5. One atom R contributes 4 electrons. 6. Each atom R contributes one electron. 7. Atom R shares four of its valence electrons each with 4 atoms of Q

8. molecule with the formula RQ4.

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c) For Group 1, 1. Going down the group ,atomic size increases 2. the valence electron becomes further away from the nucleus

3. Forces of attraction between nucleus and the valence electron becomes weaker.

4. It is easier for the atom to donate / release the valence electrons. 5. The reactivity increases down the group For Group 17 elements ,

6. Atomic size increases when descending the group 7. The valence electrons become further away from nucleus.

8. Forces of attraction between the nucleus and the outermost occupied shell become weaker

9. It is more difficult for the atom to accept /gain/receive electrons.

10.The reactivity decreases down the Group

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9) a) i) 1. atomic radius increases as we go down the group 18 elements 2. more number of shells is needed to fill the increasing number of electrons present in the

atoms. 3. melting points increases down the group. 4. atomic size increases down the group.

5. attraction forces between atoms become stronger. 6. more heat is needed to overcome this stronger force of attraction.

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ii) 1. Helium – gas used to fill airships/weather/fill up the diver’s oxygen tank

2. Neon- used in advertising lights/television tubes 3. Argon – used to fill up light bulbs / provide inert atmosphere for welding at high

temperature

4. Krypton – used in lasers to repair retina of the eye/used to fill up photographic flash lamps.

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b) i) 1. the valence electrons in the group 18 atoms are stable / (duplet and octet) while in group

17, the atoms have 7 valence electrons which is unstable. 2. in order to achieve stable electron arrangement, each atom of Group 17 elements need to share its valence electron with another atom.

3. for group 18 elements, the atoms need not have to share their valence electrons.

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ii) 1. The reactivity decreases. 2. In chemical reaction, halogen atoms need to gain one electron (into their outermost

shell)

3. The atomic size of halogens increases down the group/ the outermost occupied shell of each atom becomes further from nucleus.

4. The strength of nucleus to attract electron becomes weaker.

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10.