Question

1. practice: use the gizmo to answer the following questions. a. how many electrons are in a neutral atom of lithium? ______ b. how many neutrons are in an atom of mg - 25? ____ c. what is the mass number of an atom with 5 protons and 7 neutrons? ____ d. when an atom is charged, it is called an ion. how many electrons are in o²⁻? ____ e. how many electrons are in mg²⁺? ______

Explanation:

Step1: Recall atomic number of lithium

The atomic number of lithium (Li) is 3. In a neutral atom, the number of electrons equals the atomic number. So, a neutral atom of lithium has 3 electrons.

Step2: Determine neutrons in Mg - 25

The mass number of Mg - 25 is 25, and the atomic number of magnesium (Mg) is 12. The number of neutrons = mass number - atomic number. So, number of neutrons = 25 - 12 = 13.

Step3: Calculate mass number

The mass number is the sum of protons and neutrons. Given 5 protons and 7 neutrons, mass number = 5 + 7 = 12.

Step4: Find electrons in O²⁻

The atomic number of oxygen (O) is 8. In O²⁻, it has gained 2 electrons. So the number of electrons = 8+ 2 = 10.

Step5: Find electrons in Mg²⁺

The atomic number of magnesium (Mg) is 12. In Mg²⁺, it has lost 2 electrons. So the number of electrons = 12 - 2 = 10.

Answer:

A. 3
B. 13
C. 12
D. 10
E. 10