Question

chemistry atomic structure practice i
x = element symbol
a = mass number # of protons (p) + # neutrons (n)
z = atomic number # of protons
n = # of neutrons
a - z = n
a typical isotopic symbol takes this form: $_z^a x$
ex. the isotopic symbol for fluorine would be $_{9}^{19}f$
fill in the missing items in the table below.
name symbol z a #p #e #n isotopic symbol
na 23
17 35
potassium 39
fill in the missing items in the table below.
name symbol z a #p #e #n isotopic symbol
p 31
iron 56
127 53
fill in the missing items in the table below.
name symbol z a #p #e #n isotopic symbol
silver 108
36 84
w 184

Explanation:

Step1: Recall atomic - structure relationships

Atomic number ($Z$) = number of protons ($\#p$), for a neutral atom, number of electrons ($\#e$) = number of protons ($\#p$), number of neutrons ($\#n$)=$A - Z$, and isotopic symbol is $^{A}_{Z}X$.

Step2: First table - row 1 (Sodium)

The symbol is $Na$. Atomic number of sodium ($Z$) is 11. Since $A = 23$, $\#p=Z = 11$, $\#e=\#p = 11$, $\#n=A - Z=23 - 11 = 12$, and isotopic symbol is $^{23}_{11}Na$.

Step3: First table - row 2 (Chlorine)

$Z = 17$, $A = 35$. So $\#p = 17$, $\#e=\#p = 17$, $\#n=A - Z=35 - 17 = 18$, symbol is $Cl$, and isotopic symbol is $^{35}_{17}Cl$.

Step4: First table - row 3 (Potassium)

Symbol of potassium is $K$. Atomic number of potassium ($Z$) is 19. Since $A = 39$, $\#p=Z = 19$, $\#e=\#p = 19$, $\#n=A - Z=39 - 19 = 20$, and isotopic symbol is $^{39}_{19}K$.

Step5: Second table - row 1 (Phosphorus)

Symbol is $P$. Atomic number of phosphorus ($Z$) is 15. Since $A = 31$, $\#p=Z = 15$, $\#e=\#p = 15$, $\#n=A - Z=31 - 15 = 16$, and isotopic symbol is $^{31}_{15}P$.

Step6: Second table - row 2 (Iron)

Symbol of iron is $Fe$. Atomic number of iron ($Z$) is 26. Since $A = 56$, $\#p=Z = 26$, $\#e=\#p = 26$, $\#n=A - Z=56 - 26 = 30$, and isotopic symbol is $^{56}_{26}Fe$.

Step7: Second table - row 3 (Iodine)

$Z = 53$, $A = 127$. So $\#p = 53$, $\#e=\#p = 53$, $\#n=A - Z=127 - 53 = 74$, symbol is $I$, and isotopic symbol is $^{127}_{53}I$.

Step8: Third table - row 1 (Silver)

Symbol of silver is $Ag$. Atomic number of silver ($Z$) is 47. Since $A = 108$, $\#p=Z = 47$, $\#e=\#p = 47$, $\#n=A - Z=108 - 47 = 61$, and isotopic symbol is $^{108}_{47}Ag$.

Step9: Third table - row 2 (Krypton)

$Z = 36$, $A = 84$. So $\#p = 36$, $\#e=\#p = 36$, $\#n=A - Z=84 - 36 = 48$, symbol is $Kr$, and isotopic symbol is $^{84}_{36}Kr$.

Step10: Third table - row 3 (Tungsten)

Symbol is $W$. Atomic number of tungsten ($Z$) is 74. Since $A = 184$, $\#p=Z = 74$, $\#e=\#p = 74$, $\#n=A - Z=184 - 74 = 110$, and isotopic symbol is $^{184}_{74}W$.

Answer:

Name	Symbol	Z	A	#p	#e	#n	Isotopic Symbol
Chlorine	Cl	17	35	17	17	18	$^{35}_{17}Cl$
Potassium	K	19	39	19	19	20	$^{39}_{19}K$
Phosphorus	P	15	31	15	15	16	$^{31}_{15}P$
Iron	Fe	26	56	26	26	30	$^{56}_{26}Fe$
Iodine	I	53	127	53	53	74	$^{127}_{53}I$
Silver	Ag	47	108	47	47	61	$^{108}_{47}Ag$
Krypton	Kr	36	84	36	36	48	$^{84}_{36}Kr$
Tungsten	W	74	184	74	74	110	$^{184}_{74}W$