Question

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.
1 2 1
$^{36}s$
26 23 32
$^{27}al$
2 4 2
cr 53

Explanation:

Step1: Recall atomic number and mass - number relationships

The mass - number ($A$) is the sum of protons and neutrons, and the atomic number ($Z$) is equal to the number of protons. For a neutral atom, the number of electrons is equal to the number of protons.

Step2: For $^{36}S$

The atomic number of sulfur ($S$) from the periodic table is $Z = 16$. So the number of protons is 16, the number of electrons in a neutral atom is 16. The mass - number $A=36$, and the number of neutrons $n=A - Z=36 - 16 = 20$.

Step3: For the element with 26 protons

From the periodic table, the element with 26 protons is iron ($Fe$). The mass - number $A$ (sum of protons and neutrons) is $26+23 = 49$. The number of electrons in a neutral atom is 26.

Step4: For $^{27}Al$

The atomic number of aluminum ($Al$) is 13. So the number of protons is 13, the number of electrons in a neutral atom is 13, and the number of neutrons $n=27 - 13 = 14$.

Step5: For the element with 2 protons

The element with 2 protons is helium ($He$). The mass - number $A$ (sum of protons and neutrons) is $2 + 4=6$. The number of electrons in a neutral atom is 2.

Step6: For $Cr$

The atomic number of chromium ($Cr$) is 24. If the number of neutrons is 53, the mass - number $A=24 + 53=77$. The number of electrons in a neutral atom is 24.

Answer:

Element	Protons	Neutrons	Electrons	Mass - number
$Fe$	26	23	26	49
$^{27}Al$	13	14	13	27
$He$	2	4	2	6
$^{77}Cr$	24	53	24	77