The table below gives the numbers of protons, electrons, and neutrons in four atoms.
| Atom | Number of protons | Number of neutrons | Number of electrons |
|---|---|---|---|
| 1 | 9 | 8 | 9 |
| 2 | 9 | 9 | 8 |
| 3 | 9 | 9 | 10 |
| 4 | 9 | 10 | 9 |
Based on the table, which atom has a charge of -1?
Answer (2)
Calculate the charge of each atom by subtracting the number of electrons from the number of protons.
Atom 1 has a charge of 9 − 9 = 0 .
Atom 2 has a charge of 9 − 8 = + 1 .
Atom 3 has a charge of 9 − 10 = − 1 .
Atom 4 has a charge of 9 − 9 = 0 .
Therefore, Atom 3 has a charge of -1, so the answer is 3 .
Explanation
Understanding the Problem We are given a table with the number of protons, neutrons, and electrons for four different atoms. We need to determine which atom has a charge of -1. The charge of an atom is determined by the difference between the number of protons (positive charge) and the number of electrons (negative charge).
Calculating the Charge of Each Atom To find the charge of each atom, we subtract the number of electrons from the number of protons.
Atom 1 Charge Atom 1: Charge = Number of protons - Number of electrons = 9 − 9 = 0
Atom 2 Charge Atom 2: Charge = Number of protons - Number of electrons = 9 − 8 = + 1
Atom 3 Charge Atom 3: Charge = Number of protons - Number of electrons = 9 − 10 = − 1
Atom 4 Charge Atom 4: Charge = Number of protons - Number of electrons = 9 − 9 = 0
Identifying the Atom with Charge -1 Based on the calculations, Atom 3 has a charge of -1.
Examples
Understanding the charge of atoms is crucial in chemistry. For example, when designing batteries, chemists need to know how ions will move and interact. If an atom has a negative charge, it will be attracted to positive terminals, and vice versa. This principle is also used in electroplating, where a metal coating is applied to a surface using charged ions.
Atom 3 has a charge of -1, as it has 9 protons and 10 electrons, resulting in a charge calculated as 9 − 10 = − 1 .
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