) An ion of iodine (I) has 53 protons and 54 electrons. Is it an anion or a cation? What is the charge on the ion? (include sign) (b) Write the atomic symbol for an ion of zinc (Zn) containing 30 protons, 37 neutrons, and 28 electrons. Do
The Correct Answer and Explanation is:
(a) Iodine Ion
An ion of iodine has:
- 53 protons
- 54 electrons
To determine if this is an anion or cation, we compare the number of protons and electrons:
- Protons (positive charge): 53
- Electrons (negative charge): 54
Since electrons outnumber protons, the ion has more negative charge, making it a negatively charged ion, also known as an anion.
To find the charge: Charge=Number of protons−Number of electrons=53−54=−1\text{Charge} = \text{Number of protons} – \text{Number of electrons} = 53 – 54 = -1
✅ Answer:
- It is an anion
- The charge is –1
(b) Zinc Ion Symbol
We are told:
- 30 protons → This identifies the element as zinc (Zn).
- 37 neutrons
- 28 electrons
Step 1: Determine Mass Number (A)
The mass number (A) is the sum of protons and neutrons: A=30+37=67A = 30 + 37 = 67
Step 2: Determine Ion Charge
Charge=Number of protons−Number of electrons=30−28=+2\text{Charge} = \text{Number of protons} – \text{Number of electrons} = 30 – 28 = +2
This zinc ion has lost two electrons, so it is a cation with a +2 charge.
Step 3: Write the Atomic Symbol
The atomic symbol is written in this form: ZASymbolCharge^{A}_{Z}\text{Symbol}^{\text{Charge}}
Where:
- A = mass number = 67
- Z = atomic number (protons) = 30
- Symbol = Zn
- Charge = +2
✅ Answer:
3067Zn2+^{67}_{30}\text{Zn}^{2+}
Explanation
Ions are atoms that have gained or lost electrons, resulting in a net charge. When an atom gains electrons, it becomes negatively charged and is called an anion. When it loses electrons, it becomes positively charged and is called a cation. In part (a), an iodine ion has 53 protons and 54 electrons. Since electrons are negatively charged, having more electrons than protons means the atom has an overall negative charge. Subtracting protons from electrons (53 – 54) gives –1. Thus, the iodine ion is an anion with a –1 charge, commonly written as I⁻.
In part (b), a zinc ion has 30 protons and 28 electrons. Since protons outnumber electrons, the atom has lost electrons and has a positive charge. Subtracting gives a charge of +2 (30 – 28 = +2), making it a cation. The number of neutrons doesn’t affect charge but contributes to the atomic mass. Adding protons and neutrons gives a mass number of 67. Therefore, the full atomic symbol is written as ⁶⁷₃₀Zn²⁺, showing the mass number, atomic number, and charge. This notation is important in chemistry because it tells you both the identity and state of the ion, which affects how it interacts in chemical reactions.
