Q43E - Chemistry (OpenStax)

Question

Write a symbol for each of the following neutral isotopes. Include the atomic number and mass number for each. 

(a) the alkali metal with 11 protons and a mass number of 23 

(b) the noble gas element with 75 neutrons in its nucleus and 54 electrons in the neutral atom 

(c) the isotope with 33 protons and 40 neutrons in its nucleus 

(d) the alkaline earth metal with 88 electrons and 138 neutrons

Step-by-Step Solution

Answer

a. Symbol – ²³Na₁₁

b. Symbol – ¹²⁹Xe₅₄

c. Symbol - ⁷³As₃₃

d. Symbol – ²²⁶Ra₈₈

Step 1: General Representation

Number ^ZX_Y Atomic Number

Step 2: Alkali metal symbol

Number of protons = Atomic Number. Sodium has atomic number 11 and mass number 23. Thus, symbol is ²³Na₁₁

Step 3: Noble gas symbol

Numbers of electrons = numbers of Protons for a neutral atom. So, the element has 54 protons. Mass number is=75+54 =129. Thus, the element is Xenon and symbol is ²⁹Xe₅₄

Step 4: Isotope symbol

Mass number = 40+33 = 73, atomic number is 33. Element is Arsenic. Thus, the symbol is ⁷³As₃₃

Step 5: Alkaline earth metal symbol

In this element atomic number is 88. As numbers of electrons = numbers of Protons for a neutral atom, Mass number is =138+88 =216. The element is Radon. Thus, the symbol is ²²⁶Ra₈₈