5 30 pts A new element named A was discovered recently It co

5. (30 pts). A new element, named A, was discovered recently. It consists of three isotopes, A-30, A-34, and A-37, whose masses and natural abundances are listed below A-30 A-34 A-37 36.754 Isotopic rn 30.025 34.1231 25.010 28.022 a) Write the general equation that is used to calculate the chemical atomic mass. b) Calculate the chemical atomic mass of element A An ion of element A had a charge many protons of 2+ and was found to contain 14 electrons. How and neutron does the ion have? Write the complete symbol for this ion. c)

Solution

Ans. 5a. Average chemical atomic mass =

(% ³⁰A x its atomic mass) + (% ³⁴A x its atomic mass) + (% ³⁷A x its atomic mass)

#b. % ³⁷A (abundance) = 100 % - (% ³⁰A + % ³⁴A)

= 100 % - (25.010 % + 28.022 %)

= 46.968 %

Now, putting the values in above #a expression-

Average chemical atomic mass =

(25.010 % x 30.025 amu) + (28.022 % x 34.1231 amu) + (46.968 % x 36.754 amu)

= (0.25010 x 30.025 amu) + (0.28022 x 34.1231 amu) + (0.46968 x 36.754 amu)

= 7.5092525 amu + 9.561975082 amu + 17.26261872 amu

= 34.333846302 amu

= 34.3338 amu

# c. Loss of 1 electron contributes gain of +1 charge on the atom.

Since, the atom has +2 unit charge, it must have lost 2 electrons.

After losing 2 electrons (to get a +2 unit charge), the atom still has 14 electrons.

So, total number of electrons in atom = No. of electrons it has + No. of electrons lost

                                                            = 14 + 2

                                                            = 16

# Number of protons in a neutral atom is generally equal to number of electrons, so that total negative charge (on electrons) is equal to total positive charge (on protons) and the net charge becomes zero- or, atom is neutral.

So, number of protons = 16

# Number of neutrons is generally equal to number of protons.

So,

            Number of neutrons = 16