Question

using the table, how many neutrons does argon have? * (0.5 points)
element standard atomic notation atomic mass atomic number number of protons number of electrons number of neutrons charge
magnesium 12 +2
calcium $_{20}^{41}ca$
fluorine 19 -1
phosphorous $_{15}^{31}p^{3 - }$
sulfur 31
oxygen 8 -2
potassium $_{19}^{39}k^{+1}$
argon 40
boron 5 0
hydrogen $_{1}^{3}h$
68 98 +6
120 50 +4
7 10 13
$_{13}^{27}al^{3+}$

Explanation:

Step1: Recall neutron - proton - mass relationship

The atomic mass is approximately the sum of protons and neutrons. The atomic number of argon is 18 (a known fact from the periodic table, though not given in the table). From the table, the atomic mass of argon is 40.

Step2: Calculate number of neutrons

Let the number of neutrons be $n$, number of protons be $p$ and atomic mass be $A$. We know that $A=p + n$. Since $p = 18$ and $A=40$, then $n=A - p$. So $n=40 - 18$.
$n = 22$

Answer:

22