Question

examine the mass spectrum of silicon below. mass spectrum of silicon (q = +1) 1 0.5 28 29 30 m/q 1. what do these isotopes have in common, and what is different about them? (a) each isotope has the same number of electrons but different numbers of neutrons. (b) each isotope has the same atomic number but different numbers of electrons. (c) each isotope has the same atomic number but different numbers of neutrons. (d) each isotope has the same mass number but different numbers of protons. 2. use the data above to calculate the average atomic mass for silicon. 3. an atom of silicon - 29 is also an ion with a charge of +4. which of the following statements is false? (a) the ion has 14 protons and 15 neutrons. (b) the ion has 3 more electrons than neutrons. (c) the ion has 4 fewer electrons than protons. (d) the isotope has the same number of protons as another atom of silicon.

Explanation:

Step1: Define isotopes concept

Isotopes of an element have the same atomic number (same number of protons) but different mass - numbers due to different numbers of neutrons.

Step2: Answer question 1

The correct statement about isotopes is that each isotope has the same atomic number but different numbers of neutrons. So the answer to question 1 is B. Each isotope has the same atomic number but different numbers of neutrons.

Step3: Calculate average atomic mass for question 2

The average atomic mass ($A$) is calculated using the formula $A=\sum_{i = 1}^{n}m_i\times p_i$, where $m_i$ is the mass of the isotope and $p_i$ is its percentage abundance (in decimal form).
For silicon:
Isotope 1: $m_1 = 27.97693$ u, $p_1=0.9221$
Isotope 2: $m_2 = 28.97649$ u, $p_2 = 0.0479$
Isotope 3: $m_3=29.97379$ u, $p_3=0.0309$
$A=(27.97693\times0.9221)+(28.97649\times0.0479)+(29.97379\times0.0309)$
$A = 27.97693\times0.9221+28.97649\times0.0479 + 29.97379\times0.0309$
$A=25.89753 + 1.38897+0.92619$
$A = 28.21269\approx28.0855$ u

Step4: Analyze ion for question 3

Silicon has an atomic number of 14. For a silicon - 29 ion with a + 4 charge:
Number of protons ($p$) = 14
Number of neutrons ($n$)=$29 - 14=15$
Number of electrons ($e$)=$14 - 4 = 10$
(A) The ion has 14 protons and 15 neutrons. True.
(B) Neutrons = 15, Electrons = 10. The ion has 5 fewer electrons than neutrons, not 3 more electrons than neutrons. False.
(C) Protons = 14, Electrons = 10. The ion has 4 fewer electrons than protons. True.
(D) All silicon atoms have the same number of protons (atomic number = 14). True.
So the false statement in question 3 is B. The ion has 3 more electrons than neutrons.

Answer:

1. B. Each isotope has the same atomic number but different numbers of neutrons.
2. Approximately 28.0855 u
3. B. The ion has 3 more electrons than neutrons.