Question

for each question below, use the given information about the element to calculate or determine the missing information: (drag the correct answer to the appropriate question.)
an atom of lithium has an atomic number of 3 and an atomic mass number of 7. what is the number of electrons in an atom of lithium?
10
an atom of chlorione has an atomic number of 17 and an atomic mass number of 35. what is the number of neutrons in an atom of chlorine?
no answers chosen
an atom of magnesium has an atomic number of 12 and an atomic mass number of 24. what is the number of electrons in an atom of magnesium?
no answers chosen
an atom of boron has an atomic number of 5 and an atomic mass number of 11. what is the number of neutrons in an atom of boron?
no answers chosen
an atom of oxygen has an atomic number of 8 and an atomic mass number of 16. what is the number of protons in an atom of oxygen?
no answers chosen
possible answers
3 12 6 16 18 8

Explanation:

Lithium's Electrons

• For a neutral atom, the number of electrons equals the atomic number.
• Lithium has an atomic number of \(3\). So, the number of electrons is \(3\).

Chlorine's Neutrons

• The formula for the number of neutrons is \(n=\text{Mass number}-\text{Atomic number}\).
• Chlorine has a mass number of \(35\) and an atomic number of \(17\).
• \(n = 35-17=18\).

Magnesium's Electrons

• For a neutral atom, electrons = atomic number.
• Magnesium has an atomic number of \(12\). So, electrons = \(12\).

Boron's Neutrons

• Using \(n=\text{Mass number}-\text{Atomic number}\).
• Boron has a mass number of \(11\) and atomic number \(5\).
• \(n=11 - 5=6\).

Oxygen's Protons

• Protons = atomic number.
• Oxygen has an atomic number of \(8\). So, protons = \(8\).

Answer:

• Lithium: \(3\)
• Chlorine: \(18\)
• Magnesium: \(12\)
• Boron: \(6\)
• Oxygen: \(8\)