Question

chapter 2 retake version 3

1. which atom has the smallest number of neutrons?

a) carbon - 14 b) nitrogen - 14 c) oxygen - 16 d) fluorine - 19 e) neon - 20

1. which atom has the largest number of neutrons?

a) phosphorus - 30 b) chlorine - 37 c) potassium - 39 d) argon - 40 e) calcium - 40

1. there are ____ electrons, __ protons, and ____ neutrons in an atom of

132
54xe.
a) 132, 132, 54
b) 54, 54, 132
c) 78, 78, 54
d) 54, 54, 78
e) 78, 78, 132

1. different isotopes of a particular element contain different numbers of ______.

a) protons b) neutrons c) protons and neutrons d) protons, neutrons, and electrons
e) none of the above is correct.

1. an element in the upper right corner of the periodic table ______.

a) is either a metal or metalloid b) is definitely a metal c) is either a metalloid or a non - metal
d) is definitely a non - metal e) is definitely a metalloid

1. an element that appears in the lower left corner of the periodic table is ______.

a) either a metal or metalloid b) definitely a metal c) either a metalloid or a non - metal
d) definitely a non - metal e) definitely a metalloid

1. elements in the same group of the periodic table typically have ______.

a) similar mass numbers b) similar physical properties only
c) similar chemical properties only d) similar atomic masses
e) similar physical and chemical properties

1. potassium is a ____ and chlorine is a ____.

a) metal, nonmetal b) metal, metal c) metal, metalloid d) metalloid, nonmetal
e) nonmetal, metal

1. lithium is a ____ and magnesium is a ____.

a) nonmetal, metal b) nonmetal, nonmetal c) metal, metal d) metal, metalloid
e) metalloid, metalloid

1. the formula weight of aluminum sulfate (al2(so4)3) is ______ amu.

a) 342.15 b) 123.04 c) 59.04 d) 150.14 e) 273.06

1. the formula weight of silver chromate (ag2cro4) is ______ amu.

a) 159.87 b) 223.87 c) 331.73 d) 339.86 e) 175.87

1. the mass % of f in the binary compound krf2 is ______.

a) 18.48 b) 45.38 c) 68.80 d) 81.52 e) 31.20

Explanation:

Step1: Recall neutron - proton relationship

Number of neutrons = Mass number - Atomic number. For carbon - 14, atomic number of C is 6, so neutrons = 14 - 6 = 8. For nitrogen - 14, atomic number of N is 7, so neutrons = 14 - 7 = 7. For oxygen - 16, atomic number of O is 8, so neutrons = 16 - 8 = 8. For fluorine - 19, atomic number of F is 9, so neutrons = 19 - 9 = 10. For neon - 20, atomic number of Ne is 10, so neutrons = 20 - 10 = 10.

Step2: Determine answer for question 1

The atom with the smallest number of neutrons is nitrogen - 14. So the answer for 1 is B.

Step3: Calculate neutrons for question 2

For phosphorus - 30, atomic number of P is 15, neutrons = 30 - 15 = 15. For chlorine - 37, atomic number of Cl is 17, neutrons = 37 - 17 = 20. For potassium - 39, atomic number of K is 19, neutrons = 39 - 19 = 20. For argon - 40, atomic number of Ar is 18, neutrons = 40 - 18 = 22. For calcium - 40, atomic number of Ca is 20, neutrons = 40 - 20 = 20. The atom with the largest number of neutrons is argon - 40. So the answer for 2 is D.

Step4: Recall sub - atomic particle numbers for $_{54}^{132}$Xe

The atomic number is 54, so number of protons = 54, number of electrons = 54 (for neutral atom), and number of neutrons = 132 - 54 = 78. So the answer for 3 is D.

Step5: Recall isotope definition

Isotopes of an element have the same number of protons but different numbers of neutrons. So the answer for 4 is B.

Step6: Recall periodic table location

Elements in the upper right - corner of the periodic table are non - metals. So the answer for 5 is D.

Step7: Recall periodic table location

Elements in the lower left - corner of the periodic table are metals. So the answer for 6 is B.

Step8: Recall group properties

Elements in the same group of the periodic table typically have similar chemical properties. So the answer for 7 is C.

Step9: Recall element type

Potassium is a metal and chlorine is a non - metal. So the answer for 8 is A.

Step10: Recall element type

Lithium is a metal and magnesium is a metal. So the answer for 9 is C.

Step11: Calculate formula weight of $Al_2(SO_4)_3$

Atomic weight of Al = 26.98 amu, S = 32.07 amu, O = 16.00 amu. Formula weight = 2×26.98+3×(32.07 + 4×16.00)=53.96+3×(32.07 + 64.00)=53.96+3×96.07=53.96 + 288.21=342.17≈342.15 amu. So the answer for 10 is A.

Step12: Calculate formula weight of $Ag_2CrO_4$

Atomic weight of Ag = 107.87 amu, Cr = 52.00 amu, O = 16.00 amu. Formula weight = 2×107.87+52.00 + 4×16.00=215.74+52.00+64.00=331.74≈331.73 amu. So the answer for 11 is C.

Step13: Calculate mass % of F in $KrF_2$

Atomic weight of Kr = 83.80 amu, F = 19.00 amu. Molar mass of $KrF_2$=83.80 + 2×19.00=83.80+38.00 = 121.80 amu. Mass % of F=$\frac{2×19.00}{121.80}\times100\%=\frac{38.00}{121.80}\times100\%\approx31.20\%$. So the answer for 12 is E.

Answer:

1. B. nitrogen - 14
2. D. argon - 40
3. D. 54, 54, 78
4. B. neutrons
5. D. is definitely a non - metal
6. B. definitely a metal
7. C. similar chemical properties only
8. A. metal, nonmetal
9. C. metal, metal
10. A. 342.15
11. C. 331.73
12. E. 31.20