Question

1. fill in the following chart. dont forget to come the isotope symbol for each atom or ion. example: 16 32s^ - 2

element symbol|atomic number|mass number|# of protons|# of neutrons|# of electrons
80 200hg|80|200|80|120|80
k|19|39|19|20|18
24|24| | |28|21
i| |127|53| |54
15 31p| | | | |

38	88			36
79			118	79

56 137ba^ + 2| | | | |

Explanation:

Step1: Recall atomic - related concepts

The atomic number ($Z$) is equal to the number of protons. The mass number ($A$) is the sum of protons and neutrons ($A = p + n$). For a neutral atom, the number of electrons is equal to the number of protons. For an ion, the number of electrons is adjusted according to the charge.

Step2: Second - row element

The number of protons is 19, so the element is potassium ($K$). The mass number is $19 + 20=39$. Since there are 18 electrons and 19 protons, it is a $K^+$ ion. The isotope symbol is $_{19}^{39}K^+$.

Step3: Third - row element

The atomic number is 24, so the element is chromium ($Cr$). The number of protons is 24. The number of neutrons is 28, so the mass number is $24 + 28 = 52$. Since there are 21 electrons and 24 protons, it is a $Cr^{3 + }$ ion. The isotope symbol is $_{24}^{52}Cr^{3+}$.

Step4: Fourth - row element

The number of protons is 53, so the element is iodine ($I$). The mass number is 127. Since there are 54 electrons and 53 protons, it is an $I^-$ ion. The isotope symbol is $_{53}^{127}I^-$.

Step5: Fifth - row element

The element is phosphorus ($P$). The atomic number is 15, the mass number is 31. The number of protons is 15, the number of neutrons is $31 - 15=16$. Since it is $P^{3 - }$, the number of electrons is $15 + 3 = 18$. The isotope symbol is $_{15}^{31}P^{3-}$.

Step6: Sixth - row element

The atomic number is 38, so the element is strontium ($Sr$). The mass number is 88. The number of protons is 38. The number of neutrons is $88 - 38 = 50$. Since there are 36 electrons and 38 protons, it is a $Sr^{2+}$ ion. The isotope symbol is $_{38}^{88}Sr^{2+}$.

Step7: Seventh - row element

The atomic number is 79, so the element is gold ($Au$). The mass number is $79+118 = 197$. The number of protons is 79. Since there are 79 electrons, it is a neutral $Au$ atom. The isotope symbol is $_{79}^{197}Au$.

Step8: Eighth - row element

The element is barium ($Ba$). The atomic number is 56, the mass number is 137. The number of protons is 56. The number of neutrons is $137 - 56 = 81$. Since it is $Ba^{2+}$, the number of electrons is $56 - 2 = 54$. The isotope symbol is $_{56}^{137}Ba^{2+}$.

Answer:

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