Problem 30 - Chemistry: The Central Science

Question

Fill in the gaps in the following table, assuming each column represents a neutral atom. $$ \begin{array}{l|l|l|l|l|l} \hline \text { Symbol } & { }^{89} \mathrm{Y} & & & & \\ \text { Protons } & & 78 & & & 89 \\ \text { Neutrons } & & & 123 & & \\ \text { Electrons } & & & 81 & 50 & \\ \text { Mass no. } & & 195 & & 119 & 227 \\ \hline \end{array} $$

Step-by-Step Solution

Answer

The completed table is as follows: \( \begin{array}{l|l|l|l|l|l} \hline \text { Symbol } & { }^{89} \mathrm{Y} & \mathrm{Pt} & \mathrm{Tl} & \mathrm{Sn} & \\ \text { Protons } & 89 & 78 & 81 & 50 & 89 \\ \text { Neutrons } & 111 & 117 & 123 & 69 & 138 \\ \text { Electrons } & 89 & 78 & 81 & 50 & 89 \\ \text { Mass no. } & 200 & 195 & 204 & 119 & 227 \\ \hline \end{array} \)

Step 1: Finding the element's symbol for 78 protons

According to the periodic table, the element with the atomic number (number of protons) 78 is platinum (Pt).

Step 2: Finding the number of electrons for a neutral ^{89}Y atom

A neutral atom has the same number of electrons as protons. In the case of Yttrium (Y), it has 89 protons, so it must have 89 electrons.

Step 3: Finding the number of neutrons for a mass number of 195 and 78 protons

We can find the number of neutrons using the formula A = Z + N. In this case, the mass number (A) is 195 and the number of protons (Z) is 78, which gives us N = 195 - 78 = 117 neutrons.

Step 4: Finding the element's symbol for 81 electrons

A neutral atom has equal numbers of protons and electrons. Therefore, an atom with 81 electrons has 81 protons. The element with 81 protons is Thallium (Tl).

Step 5: Finding the number of protons for an atom with 50 electrons

A neutral atom has equal numbers of protons and electrons. Therefore, an atom with 50 electrons has 50 protons. The element with 50 protons is Tin (Sn).

Step 6: Finding the number of neutrons for an atom with 89 protons and mass number 227

We can find the number of neutrons using the formula A = Z + N. In this case, the mass number (A) is 227 and the number of protons (Z) is 89, which gives us N = 227 - 89 = 138 neutrons. The completed table is as follows: $$ \begin{array}{l|l|l|l|l|l} \hline \text { Symbol } & { }^{89} \mathrm{Y} & \mathrm{Pt} & \mathrm{Tl} & \mathrm{Sn} & \\\ \text { Protons } & 89 & 78 & 81 & 50 & 89 \\\ \text { Neutrons } & 111 & 117 & 123 & 69 & 138 \\\ \text { Electrons } & 89 & 78 & 81 & 50 & 89 \\\ \text { Mass no. } & 200 & 195 & 204 & 119 & 227 \\\ \hline \end{array} $$