Question

study guide
atomic structure and the periodic table

• know the 3 subatomic particles we discussed in class, their relative mass, charge, and location in the atom

subatomic particle charge location in atom size

• know the locations of important groups of atoms on the periodic table: alkali metals, transition metals, alkaline earth metals, halogens, noble gases, metals, nonmetals, metalloids, inner transition metals (actinides and lanthanides)
• know how to find the number of protons (p⁺), neutrons (n⁰) and electrons (e⁻) in a neutral atom of any elements i give you from the periodic table
• know the contributions of dalton, thomson, rutherford, bohr and schrodinger/heisenberg and the atomic models for dalton, thomson (plum pudding), rutherford (nuclear model), bohr (planetary model)
• dalton
• thomson
• rutherford
• bohr
• schrodinger/heisenberg
• define the following terms and describe its relative trend across a period and down a group:
• atomic radius
• ionization energy
• electronegativity
• be able to draw orbital diagrams and electron configurations for elements on the periodic table.

example problems

1. fill in the following table

symbol atomic # mass # # protons # electrons # neutrons
ta
11
184
ra²⁺
1⁺

1. calculate the average atomic mass of the unknown element. identify the element.

isotope abundance mass
x - 84 0.56% 83.913 amu
x - 86 9.86% 85.909 amu
x - 87 7.00% 85.909 amu
x - 88 82.58% 87.906 amu

1. which atom would you expect to require more energy to remove a valence electron: gallium or potassium?
2. which atom would you expect to be larger: phosphorus or sodium?
3. which atom would you expect to have the lowest attraction for a pair of electrons in a bond: magnesium or chlorine?
4. which of the following is more likely to attract electrons in a bond: carbon or potassium?
5. which of the following would you expect to require less energy to remove a valence electron: calcium or bromine?
6. which of the following atoms is larger: magnesium or barium?
7. which of the following is more likely to lose a valence electron: rubidium or sulfur?
8. which of the following has a greater pull for a pair of bonded electrons: fluorine or aluminum?
9. in the periodic table below, correctly label the following: halogens, alkaline earth metals, transition metals, noble gases, alkali metals and inner transition metals.

Explanation:

Step1: Recall average atomic mass formula

The average atomic mass ($A_{avg}$) of an element with isotopes is calculated using the formula $A_{avg}=\sum_{i = 1}^{n}(x_i\times m_i)$, where $x_i$ is the fractional - abundance of the $i$th isotope and $m_i$ is the mass of the $i$th isotope. First, convert the percentages to fractions:
$x_{84}=0.0056$, $x_{86}=0.0986$, $x_{87}=0.0700$, $x_{88}=0.8258$.

Step2: Calculate the contribution of each isotope

For isotope X - 84: $x_{84}\times m_{84}=0.0056\times83.913 = 0.4699128$
For isotope X - 86: $x_{86}\times m_{86}=0.0986\times85.909 = 8.4706274$
For isotope X - 87: $x_{87}\times m_{87}=0.0700\times86.909 = 6.08363$
For isotope X - 88: $x_{88}\times m_{88}=0.8258\times87.906 = 72.5237748$

Step3: Sum up the contributions

$A_{avg}=0.4699128 + 8.4706274+6.08363 + 72.5237748=87.547945$ amu.
Looking at the periodic table, the element with an average atomic mass close to 87.547945 amu is Rubidium (Rb).

Answer:

The average atomic mass of the element is approximately 87.55 amu and the element is Rubidium (Rb).

1. Gallium has a higher ionization energy than Potassium. This is because ionization energy increases across a period and decreases down a group. Gallium is in Group 13 and Period 4, while Potassium is in Group 1 and Period 4. Potassium has a single valence electron in the 4s orbital and is more likely to lose it easily due to its low effective - nuclear charge compared to Gallium.