1. There are four isotopes of calcium. Their mass numbers are 40, 42, 43, and 44.

• Please write the complete chemical symbol (superscript and subscript) for each isotope.
• How many neutrons are in an atom of each isotope?
• How many neutrons, protons, and electrons are present in a ⁴²Ca²⁺ ion?

2. Give the chemical symbol, with its superscripted mass number, for:

• The element with 42 protons and 54 neutrons
• The ion with 15 protons, 16 neutrons, and 18 electrons
• The isotope of silver that has 61 neutrons

3. How many protons, neutrons and electrons does the ⁵²Cr³⁺ ion have, respectively?

A. 24, 52, 26
B. 52, 52, 55
C. 24, 28, 26
D. 24, 28, 21
E. 24, 28, 25

4. The symbol of an ion is . Which of the following is true regarding the ion?

I. It has 92 protons.
II. It has 238 neutrons.
III. It has 88 electrons.
IV. The element X is uranium.

A. I and II only
B. I, III and IV only
C. II and IV only
D. I and IV only
E. I, II, III, and IV

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1.
— 20 neutrons

— 22 neutrons

— 23 neutrons

— 24 neutrons

— 22 neutrons, 20 protons, 18 electrons

2.
3. D
4. B