Question

1.7 1.2.4 interpret simple examples of representing elements and compounds

which isotope is more abundant?
what is the identity of element x (which element on the periodic table)?

2b. examine the isotopic symbol for a neutral atom of zinc below. use the information in the model to answer the following questions. remember that mass number is equal to the number of protons + neutrons.
number of protons:
number of electrons:
mass number:
number of neutrons:

\\(_{30}^{67}\text{zn}\\)

2c. interpret the chemical formula below.
\\(\text{ca}_3(\text{po}_4)_2\\)

question	answer
b. how many phosphorus atoms are represented?
c. how many oxygen atoms are represented?
d. how many phosphate ions, \\(\text{po}_4\\) groups, are represented?

2d. below is a particle model representing a chemical reaction. use this particle model to write a chemical equation for the reaction.

\\(\text{s}\\) + \\(\text{o=o}\\) \\(\
ightarrow\\)

chemical equation:

Explanation:

Sub - question 2B (for the \(^{67}_{30}\text{Zn}\) part)

Step 1: Determine the number of protons

The atomic number (the bottom number in the atomic symbol) represents the number of protons. For \(^{67}_{30}\text{Zn}\), the atomic number is 30, so the number of protons \(= 30\).

Step 2: Determine the number of electrons (for a neutral atom)

In a neutral atom, the number of electrons is equal to the number of protons. So the number of electrons \(= 30\).

Step 3: Determine the mass number

The mass number is the top number in the atomic symbol, so for \(^{67}_{30}\text{Zn}\), the mass number \(= 67\).

Step 4: Determine the number of neutrons

The number of neutrons is calculated by subtracting the atomic number from the mass number. So number of neutrons \(=\) mass number \(-\) atomic number \(= 67 - 30=37\).

Part A: Number of calcium atoms

In the formula \(\text{Ca}_3(\text{PO}_4)_2\), the subscript of \(\text{Ca}\) is 3, so the number of calcium atoms is 3.

Part B: Number of phosphorus atoms

In the formula, the subscript of \(\text{P}\) inside the parentheses is 1, and the subscript outside the parentheses is 2. So we multiply them: \(1\times2 = 2\), so the number of phosphorus atoms is 2.

Part C: Number of oxygen atoms

The subscript of \(\text{O}\) inside the parentheses is 4, and the subscript outside the parentheses is 2. So we calculate \(4\times2=8\), so the number of oxygen atoms is 8.

Part D: Number of phosphate ions (\(\text{PO}_4\) groups)

The subscript outside the parentheses of \((\text{PO}_4)\) is 2, so the number of phosphate ions is 2.

Step 1: Identify the reactants and products from the particle model

• Reactants: We have 2 atoms of sulfur (S) and 3 molecules of oxygen (\(\text{O}_2\)).
• Products: We have 2 molecules of sulfur trioxide (\(\text{SO}_3\)) (since each product molecule has 1 S and 3 O atoms, and there are 2 such molecules).

Step 2: Write the chemical equation

The reactants are \(\text{S}\) and \(\text{O}_2\), and the product is \(\text{SO}_3\). Balancing the equation:

• For sulfur: On the left, we have 2 S atoms. On the right, in \(\text{SO}_3\), if we have 2 molecules of \(\text{SO}_3\), we have 2 S atoms.
• For oxygen: On the left, 3 molecules of \(\text{O}_2\) give \(3\times2 = 6\) O atoms. On the right, 2 molecules of \(\text{SO}_3\) give \(2\times3=6\) O atoms.
• So the balanced chemical equation is \(2\text{S}+3\text{O}_2

ightarrow2\text{SO}_3\).

Answer:

• Number of protons: \(30\)
• Number of electrons: \(30\)
• Mass number: \(67\)
• Number of neutrons: \(37\)

Sub - question 2C (for the \(\text{Ca}_3(\text{PO}_4)_2\) part)