Question

₁₅³¹p³⁻
element: _____________
atomic #: _____________

electrons:___________

atomic mass: ___________
₁₀²¹ne
element: _____________
atomic #: _____________

electrons:___________

neutrons: ___________

Explanation:

For $\boldsymbol{_{15}^{31}P^{3-}}$:

Step1: Identify the element

The symbol is P, so the element is Phosphorus.

Step2: Determine atomic number

Atomic number is the bottom number, so atomic # = 15.

Step3: Calculate number of electrons

For a neutral atom, electrons = protons (atomic number). But this is a $3^-$ ion, so it has gained 3 electrons. So electrons = 15 + 3 = 18.

Step4: Find atomic mass

Atomic mass is the top number, so atomic mass = 31.

For $\boldsymbol{_{10}^{21}Ne}$:

Step1: Identify the element

The symbol is Ne, so the element is Neon.

Step2: Determine atomic number

Atomic number is the bottom number, so atomic # = 10.

Step3: Calculate number of electrons

For a neutral atom, electrons = protons (atomic number), so electrons = 10.

Step4: Find number of neutrons

Neutrons = atomic mass - atomic number = 21 - 10 = 11.

Answer:

For $_{15}^{31}P^{3-}$:

• element: Phosphorus
• atomic #: 15
• # electrons: 18
• atomic mass: 31

For $_{10}^{21}Ne$:

• element: Neon
• atomic #: 10
• # electrons: 10
• # neutrons: 11