Question

1. fill in the following chart. don’t forget to come the isotope symbol for each atom or ion. example: ( 16 32 s^{-2} )

element symbol	atomic number	mass number	# of protons	# of neutrons	# of electrons
( 19 39 k^{+1} )			19	20	18
( 24 52 cr^{+3} )	24			28	21
( 53 127 i^{p} )		127	53		54
( 15 31 p^{-3} )
( 38 88 sr^{+2} )	38	88			36
( 79 197 au )	79			118	79
( 56 137 ba^{+2} )

Answer:

To solve this, we use the following relationships:

• Atomic number (\(Z\)) = number of protons (\(p^+\))
• Mass number (\(A\)) = number of protons (\(p^+\)) + number of neutrons (\(n^0\))
• For neutral atoms: number of electrons (\(e^-\)) = number of protons (\(p^+\))
• For ions: \(e^- = p^+ - \text{charge}\) (positive charge: lose electrons; negative charge: gain electrons)

1. \(_{80}^{200}\text{Hg}\) (Neutral atom)

Step1: Atomic number

Atomic number = number of protons = \(80\) (from isotope symbol: \(_{80}^{200}\text{Hg}\))

Step2: Mass number

Mass number = \(200\) (from isotope symbol: \(_{80}^{200}\text{Hg}\))

Step3: Number of protons

Protons = atomic number = \(80\)

Step4: Number of neutrons

Neutrons = mass number – protons = \(200 - 80 = 120\)

Step5: Number of electrons

Neutral atom: electrons = protons = \(80\)

2. \(_{19}^{39}\text{K}^{+1}\) (Ion)

Step1: Atomic number

Atomic number = number of protons = \(19\) (from isotope symbol: \(_{19}^{39}\text{K}^{+1}\))

Step2: Mass number

Mass number = \(39\) (from isotope symbol: \(_{19}^{39}\text{K}^{+1}\))

Step3: Number of protons

Protons = \(19\) (given)

Step4: Number of neutrons

Neutrons = \(20\) (given) (or \(39 - 19 = 20\))

Step5: Number of electrons

Ion (\(+1\)): \(e^- = p^+ - 1 = 19 - 1 = 18\) (matches given)

3. \(_{24}^{52}\text{Cr}^{+3}\) (Ion)

Step1: Atomic number

Atomic number = \(24\) (given)

Step2: Mass number

Mass number = protons + neutrons = \(24 + 28 = 52\) (from isotope symbol: \(_{24}^{52}\text{Cr}^{+3}\))

Step3: Number of protons

Protons = atomic number = \(24\)

Step4: Number of neutrons

Neutrons = \(28\) (given) (or \(52 - 24 = 28\))

Step5: Number of electrons

Ion (\(+3\)): \(e^- = p^+ - 3 = 24 - 3 = 21\) (matches given)

4. \(_{53}^{127}\text{I}^-\) (Ion, \(^p\) likely typo for \(-1\))

Step1: Atomic number

Atomic number = number of protons = \(53\) (from isotope symbol: \(_{53}^{127}\text{I}\))

Step2: Mass number

Mass number = \(127\) (given)

Step3: Number of protons

Protons = \(53\) (given)

Step4: Number of neutrons

Neutrons = mass number – protons = \(127 - 53 = 74\)

Step5: Number of electrons

Ion (\(-1\)): \(e^- = p^+ + 1 = 53 + 1 = 54\) (matches given)

5. \(_{15}^{31}\text{P}^{-3}\) (Ion)

Step1: Atomic number

Atomic number = number of protons = \(15\) (from isotope symbol: \(_{15}^{31}\text{P}^{-3}\))

Step2: Mass number

Mass number = \(31\) (from isotope symbol: \(_{15}^{31}\text{P}^{-3}\))

Step3: Number of protons

Protons = \(15\)

Step4: Number of neutrons

Neutrons = mass number – protons = \(31 - 15 = 16\)

Step5: Number of electrons

Ion (\(-3\)): \(e^- = p^+ + 3 = 15 + 3 = 18\)

6. \(_{38}^{88}\text{Sr}^{+2}\) (Ion)

Step1: Atomic number

Atomic number = \(38\) (given)

Step2: Mass number

Mass number = \(88\) (given)

Step3: Number of protons

Protons = atomic number = \(38\)

Step4: Number of neutrons

Neutrons = mass number – protons = \(88 - 38 = 50\)

Step5: Number of electrons

Ion (\(+2\)): \(e^- = p^+ - 2 = 38 - 2 = 36\) (matches given)

7. \(_{79}^{197}\text{Au}\) (Neutral atom)

Step1: Atomic number

Atomic number = \(79\) (given)

Step2: Mass number

Mass number = protons + neutrons = \(79 + 118 = 197\) (from isotope symbol: \(_{79}^{197}\text{Au}\))

Step3: Number of protons

Protons = \(79\) (given)

Step4: Number of neutrons

Neutrons = \(118\) (given) (or \(197 - 79 = 118\))

Step5: Number of electrons

Neutral atom: electrons = protons = \(79\) (matches given)

8. \(_{56}^{137}\text{Ba}^{+2}\) (Ion)

Step1: Atomic number

Atomic number = number of protons = \(56\) (from isotope symbol: \(_{56}^{137}\text{Ba}^{+2}\))

Step2: Mass number

Mass number = \(137\) (from isotope symbol: \(_{56}^{137}\text{Ba}^{+2}\))

Step3: Number of protons

Protons = \(56\)

Step4: Number of neutrons

Neutrons = mass number – protons = \(137 - 56 = 81\)

Step5: Number of electrons

Ion (\(+2\)): \(e^- = p^+ - 2 = 56 - 2 = 54\)

Filled Table:

Element Symbol	Atomic number	Mass number	# of protons	# of neutrons	# of electrons
\(_{19}^{39}\text{K}^{+1}\)	\(19\)	\(39\)	\(19\)	\(20\)	\(18\)
\(_{24}^{52}\text{Cr}^{+3}\)	\(24\)	\(52\)	\(24\)	\(28\)	\(21\)
\(_{53}^{127}\text{I}^-\)	\(53\)	\(127\)	\(53\)	\(74\)	\(54\)
\(_{15}^{31}\text{P}^{-3}\)	\(15\)	\(31\)	\(15\)	\(16\)	\(18\)
\(_{38}^{88}\text{Sr}^{+2}\)	\(38\)	\(88\)	\(38\)	\(50\)	\(36\)
\(_{79}^{197}\text{Au}\)	\(79\)	\(197\)	\(79\)	\(118\)	\(79\)
\(_{56}^{137}\text{Ba}^{+2}\)	\(56\)	\(137\)	\(56\)	\(81\)	\(54\)

(Note: For \(_{53}^{127}\text{I}^p\), we assumed \(^p\) is a typo for \(-1\) (iodide ion) since electrons = 54 (protons +1).)