Topics: Atom, Electron, Covalent bond Pages: 34 (5950 words) Published: February 20, 2013
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1.(i)atoms of the same element with different numbers of neutrons/different masses (1)1
(ii)79Br 35 protons, 44 neutrons, 35 electrons (1) 81Br 35 protons, 46 neutrons, 35 electrons (1)2
(iii)(1s2)2s22p63s23p63d104s24p5 (1)1

2.(i)iodide has been converted to iodine (1)
(with correct use and spelling of iodide and iodine)
The 1st experiment shows that bromine is more reactive than iodine (1) The 2nd experiment shows that chlorine is more reactive than bromine (1) Accept 1 mark for 2nd and 3rd marking points if the correct reactivity order of chlorine > bromine > iodine has been stated.3

(ii)Br2 + 2I–  2Br– + I2 (1)1

3.add AgNO3/Ag+ (to a solution of the food) (1) Ag+(aq) + Cl–(aq)  AgCl(s) (1)
degree of cloudiness/whiteness/intensity indicates relative quantity (1) sodium ion content needs to be determined as well (1)

4.(i)S (1)1
(ii)Al (1)1
(iii)B (1)1
(iv)Ca (1)1
(v)K (1)1
(vi)K (1)1

5.(i)atomic radii decrease /similar shielding /electrons added to same shell (1) number of protons in the nucleus increases (1)
nuclear attraction increases (1)3
(ii)Na2+(g)  Na3+(g) + e– : equation and state symbols (1)1
(iii)large jump (in energy) between the 4th and 5th ionisation energies (1) four electrons in outer shell so element is Si (1)2


positive ions (1) electrons (1) (must be labelled)2
(ii)the electrons move (1)1

7.(i)attraction between oppositely charged ions1

Mg and Cl both with 8 electrons in outer shell, (accept 0 electrons for Mg) Cl must have one dot to seven crosses or vice versa (1)
correct charges on each ion (1)2

(iii)MgCl2 does not conduct when solid because ions are fixed in lattice (1) H2O does not conduct as there are no free charge carriers/water molecules are uncharged (1)
MgCl2 conducts when aqueous because ions are free to move (1)3

8.To boil Cl2, van der Waals’ forces/intermolecular forces are broken (with van der Waals/intermolecular spelt correctly) (1)
To boil C, covalent bonds are broken (1)
covalent bonds are stronger than van der Waals’ forces (1)

9.removed for test

10.removed for test

11.(i)because Ca has changed from 0 to +2 (1)
and H has changed from +1 to 0 (1)2
(ii)Calcium reacts with water producing
hydrogen/H2/calcium/hydroxide/Ca(OH)2 (1) (i.e. one product) Ca(s) + H2O(l)  Ca(OH)2(aq) + H2(g) (1) (i.e. full equation) Equation would subsume both two marks2


shape (1) bond angle labelled on diagram as 107° (1)

shape (1) bond angle labelled on diagram as...
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