Chem 1010 Tutorials Tutorial 11A – Periodic Trends and the Octet ...

Chem 1010 Tutorials
Tutorial 11A – Periodic Trends and
the Octet Rule
Fall 2011
1. Arrange the following species in order of increasing size:
(a) Ar, K + , Cl – , S 2– , Ca 2+ (b) Br, Li + , Se, I – (c) P, N, As, As 3– (d) K + , P 3– , S 2– , Cl –
(e) Sc, Ba, Se (f) Na, K, F, Mg, Ne (g) Sr, Se, Cs, Ga, In (h) K + , Se 2– , Cl – , Na + , S 2–
2. Arrange the following in the expected order of increasing first ionization energy:
(a) As, Sn, Br, Sr (b) Cl, K, Mg, S (c) Na, K, F, Mg, Ne
3. Multiple choice questions:
(i) Which species does not have an octet of electrons for its outer core?
(a) C 4+ (b) P 3- (c) O 2– (d) Mg +
(ii) Which comparison of atomic and/or ionic radii is correct?
(a) K + > K (b) Ca 2+ > K + (c) Si > S (d) Kr > Xe (e) Cl > Cl –
(iii) The ion represented as 48 22Ti 3+ has…
(a) 22 electrons (b) 48 neutrons (c) 26 protons
(d) four 3d electrons (e) no 4s electrons
(iv) If the formula of an oxide is X2O3, what is the formula of the chloride of X?
(a) XCl (b) X3Cl (c) XCl3 (d) XCl6 (e) X2Cl3
4. Which of the following statements is CORRECT?
(a) The radius of an atom decreases when it forms a cation
(b) Atomic radii increase across a row (left to right) in the periodic table
(c) The radius of an atom decreases when it forms an anion
(d) Atomic radii decrease down a group in the periodic table
(e) A high Zeff increases the radius of an atom or ion
5. Using the octet rule, what is the most likely formula of the neutral binary compound formed
from Ca and N?
(a) Ca3N2 (b) Ca2N3 (c) Ca3N (d) CaN2
(e) CaN
6. Using the octet rule, what charges would be on Li and S for to each have a full valence octet of
electrons?
(a) Li – and S 6– (b) Li – and S 4+ (c) Li 2+ and S 2– (d) Li + and S 2– (e) Li + and S 4–
7. Which of the following species has the largest radius? (a) Sr 2+ (b) Br – (c) Rb + (d) Kr (e) Se 2–
8. Which of the following is correct about the periodic table?
(a) Ag is a p block element (b) Bi is a d - block metal
(c) The 4s orbital is higher in energy than the 3d orbitals (d) Zeff increases across a row
9. In each of the following pairs of elements, which has the greater negative value for electron
affinity?
(a) Se, As (b) Li, C (c) I, Sb (d) Ga, Br (e) S, P

10. Which of the following correctly orders each of these pairs of atomic and ionic radii?
(a) Na < Na + and Br < Br – and Br – < F – (b) Na < Na + and Br – < Br and F – < Br –
(c) Na + < Na and Br – < Br and Br – < F – (e) Na + < Na and Br < Br – and Br – < F –
(e) Na + < Na and Br < Br – and F – < Br –
11. According to the octet rule, what ionic charges are necessary for aluminum and sulfur so that
each has a full valence octet of electrons?
(a) Al 3+ and S 3– (b) Al 3+ and S 2– (c) Al 3+ and S 6– (d) Al 2+ and S 2– (e) Al + and S 3–
12. A metalloid has an acidic oxide of the formula R2O3. The element has no oxide of the formula
R2O5. What is the name of the element, R?
13. Which of the following statements is CORRECT?
(a) Ionization energy decreases from left to right in the periodic table because Zeff also decreases
(b) Ionization energy increases from left to right in the periodic table because Zeff also increases
(c) Ionization energy increases down a group in the periodic table because Zeff increases
(d) The ionization energy decreases down a group in the periodic table because Zeff increases
(e) None of the above
14. Which atom has the highest Zeff felt by its valence electrons?
(a) K (b) Rb (c) Ge (d) Br (e) Be
15. Which of the following most likely represents the atomic radius of a Cr atom, a Cr 2+ ion and a
Cr 3+ ion?
(a) 128 pm for Cr; 89 pm for Cr 2+ , and 63 pm for Cr 3+
(b) 128 pm for Cr; 167 pm for Cr 2+ , and 193 pm for Cr 3+
(c) 128 pm for Cr; 193 pm for Cr 2 , and 147 pm for Cr 3+
(d) 89 pm for Cr; 167 pm for Cr 2+ , and 128 pm for Cr 3+
(e) None of the above
16. What is the correct order for the size of these ions going from smallest to largest?
(a) S 2– , Se 2– , K + (b) K + , Se 2– , S 2– (c) K + , S 2– , Se 2– (d) Se 2– , S 2– , K + (e) S 2– , K + , Se 2–
Answers:
1. (a) Ca 2+ , K + , Ar, Cl - , S 2- (b) Li + , Br , Se , I - (c) N, P, As, As 3- (d) K + , Cl - , S 2- , P 3- (e) Se, Sc, Ba
(f) Ne, F, Mg, Na, K (g) Se, Ga, In, Sr, Cs (h) Na + , K + , Cl - , S 2- , Se 2-
2. (a) Sr, Sn, As, Br (b) K, Mg, S, Cl (c) K, Na, Mg, F, Ne
3. (i) a and d (ii) c (iii) e (iv) c
4. a 5. a 6. d 7. E 8. d
9. (a) Se (b) C (c) I (d) Br (e) S
10. e 11. b 12. Read the book 13. b 14.d
15. a 16. c