Periodic Table

Atomic History & Structure and Periodic Table
Practice Problems:
1. Calculate the Average Atomic Mass
Mass Abundance
Isotope 1 80 amu 30%
Isotope 2 82 amu 30%
Isotope 3 84 amu 40%
Average Atomic Mass = (Mass)(Abundance) + (Mass)(Abundance) + (Mass)(Abundance)
Average Atomic Mass = (80 amu)(0.3) + (82 amu)(0.3) + (84 amu)(0.4)
Average Mass: 82.2 amu
2. There are 2 naturally occurring isotopes of boron. Calculate the abundance of B-10 and B-11.
Average atomic mass of Boron = 10.8 amu
Average Atomic Mass = (Mass)(Abundance) + (Mass)(Abundance)
10.8 = (10 )(x) + (11)(1-x)
10.8 = 10x + 11 – 11x
0.2 = x
B-10 20% abundant
B-11 80% abundant
3. List the p, n, e of the following atoms:
16
O –2 8 protons, 8 neutrons, 10 electrons
8
4. List the p, n, e of the following atom:
Barium-140 ion that has a +2 charge
56 protons, 84 neutrons, 54 electrons
5. Write the symbol, superscript and subscript, for an atom that has:
13 p, 14 n, 10 e 27
+3
Al
13
Extended
Elemental
Symbol
21
10
18
8
65
29
Ne
O
Cu
+2
Atomic
Number
Mass
Number
Number of
Protons
Number of
Neutrons
Number of
Electrons
Name of
Isotope
10 21 10 11 10 Neon-21 0
8 18 8 10 8 Oxygen-18 0
Charge
29 65 29 36 27 Copper-65 +2

6. Does lithium have a larger value than potassium for:
a. First ionization energy - YES
b. Atomic radius - NO
c. Electronegativity - YES
d. Ionic radius - NO
7. Arrange these elements in order of decreasing atomic size: sulfur, chlorine, aluminum, and
sodium.
Sodium > Aluminum > Sulfur > Chlorine
8. Which element in each pair has the larger ionization energy
a. sodium, potassium
b. magnesium, phosphorus
9. Which particle has the larger radius in each atom/ion pair?
a. Na , Na +
b. S , S -2
10. Which element is more electronegative?
a. Cl , F
b. Mg , Ne *Most noble gases do not have electronegativity values
c. As , Ca
11. In each pair, which ion is larger?
a. Ca +2 , Mg +2
b. Cl -1 , P -3
12. Name the family that (has):
a. The highest ionization energies of any of the families - NOBLE GASES
b. The largest atomic radii of any of the families - ALKALI METALS
c. Gain 1 electron to fill its octet - HALOGENS
d. Two valence electrons - ALKALINE EARTH METALS

13. Which group of elements is brittle, but can conduct electricity?
METALLOIDS
14. Of potassium, germanium, and bromine, which element loses electrons the easiest?
Potassium – it has the lowest ionization energy
15. Predict the melting point for potassium given the following melting points:
Li = 181 o C, Na = 98 o C, Rb = 39 o C, Cs = 28 o C
Li = 181 o C, Na = 98 o C, K = 63 o C, Rb = 39 o C, Cs = 28 o C
(potassium is between Na and Rb on the periodic table, so the melting point needs to be
between sodium’s and rubidium’s)