Question

1. if you know only the following information can you always determine what the element is? (yes/no)

a. number of protons
b. number of neutrons
c. number of electrons in a neutral atom
d. number of electrons

fill in the missing items in the table below. complete the table. use a periodic table where needed. there is enough information given for each element to determine all missing numbers.

symbol	atomic number	mass number	number of protons	number of electrons	number of neutrons
k		40		19
			38	38	52
f					10
	20	41		20
	50			50	72
$^{131}$i
$^{26}$mg
		109	47	47
	1	2		1
$^{36}$s
	26			26	32
$^{27}$al
	2	4		2
cr		53

Explanation:

Step1: Determine Yes/No for each part

a. Number of protons: Atomic number = protons, unique to element → Yes.
b. Number of neutrons: Isotones exist (e.g., C-14 and N-15) → No.
c. Electrons in neutral atom: = protons = atomic number → Yes.
d. Number of electrons: Ions have variable electrons (e.g., Cl⁻ and Ar) → No.

Step2: Fill table using Z=protons=e⁻(neutral), A=protons+neutrons

²³Na: Z=11, A=23, p=11, e⁻=11, n=12; K: Z=19, p=19, n=21; Sr-90: Z=38, A=90; F-19: Z=9, A=19, p=9, e⁻=9; Ca: Z=20, p=20, n=21; Sn: Z=50, A=122; ¹³¹I: Z=53, p=53, e⁻=53, n=78; ²⁶Mg: Z=12, p=12, e⁻=12, n=14; Ag-109: Z=47, n=62; H-2: p=1, n=1; ³⁶S: Z=16, p=16, e⁻=16, n=20; Fe: Z=26, A=58, p=26; ²⁷Al: Z=13, p=13, e⁻=13, n=14; He-4: p=2, n=2; Cr: Z=24, p=24, e⁻=24, n=29.

Answer:

a. Yes
b. No
c. Yes
d. No

Symbol	Atomic Number	Mass Number	Number of Protons	Number of Electrons	Number of Neutrons
K	19	40	19	19	21
Sr	38	90	38	38	52
F	9	19	9	9	10
Ca	20	41	20	20	21
Sn	50	122	50	50	72
¹³¹I	53	131	53	53	78
²⁶Mg	12	26	12	12	14
Ag	47	109	47	47	62
H	1	2	1	1	1
³⁶S	16	36	16	16	20
Fe	26	58	26	26	32
²⁷Al	13	27	13	13	14
He	2	4	2	2	2
Cr	24	53	24	24	29