Question

For the noble gases (the Group 8A elements) 4He2, 20Ne10, 40Ar18, 84Kr36 and 132Xe54, (a) determine the number of protons and neutrons in the nucleus of each atom, and (b) determine the ratio of neutrons to protons in the nucleus of each atom. Describe any general trend you discover in the way this ratio changes with increasing atomic number.

Answer 1

Answer:

a) ⁴He₂

Protons = 2

neutrons = 2

ratio = 1:1

b) ²⁰Ne₁₀

Protons = 10

neutrons = 10

ratio = 1:1

c) ⁴⁰Ar₁₈

Protons = 18

neutrons = 22

ratio = 1.2 : 1

d) ⁸⁴Kr₃₆

Protons = 36

neutrons = 48

ratio = 1.33:1

e) ¹³²Xe₅₄

Protons = 54

neutrons = 78

ratio = 1.44 : 1

With the increase in atomic number the ratio increases.

Explanation:

Atomic number = number of protons

Mass number = number of protons + number of neutrons

So number of neutrons = mass number - number of protons

The element is represented as

$^{A}X_{Z}$

Where

A = atomic mass

Z = atomic number

a) ⁴He₂

Protons = 2

neutrons = 2

ratio = 1:1

b) ²⁰Ne₁₀

Protons = 10

neutrons = 10

ratio = 1:1

c) ⁴⁰Ar₁₈

Protons = 18

neutrons = 22

ratio = 1.2 : 1

d) ⁸⁴Kr₃₆

Protons = 36

neutrons = 48

ratio = 1.33:1

e) ¹³²Xe₅₄

Protons = 54

neutrons = 78

ratio = 1.44 : 1