Q.42E - Chemistry (OpenStax)

Question

Use the periodic table to give the name and symbol for each of the following elements:

 (a) the halogen in the same period as the alkali metal with 11 protons 

(b) the alkaline earth metal in the same period with the neutral noble gas with 18 electrons 

(c) the noble gas in the same row as an isotope with 30 neutrons and 25 protons 

(d) the noble gas in the same period as gold

Step-by-Step Solution

Answer

(a) Name – Chlorine, Symbol – Cl

(b) Name – Magnesium, Symbol – Mg and Name – Argon, Symbol – Ar

(c) Name – Krypton, Symbol - Kr

(d) Name – Radon, Symbol - Rn

Step 1: Identify the halogen element

Number of protons = atomic number. The alkali metal with 11 protons is sodium. It is placed in the 3rd period of the periodic table. If you notice the periodic table, you will find that the Halogen element present in the 3^rd period is chlorine. Thus, the element is chlorine, whose symbol is Cl.

Step 2: Identify alkaline earth metal and noble gas element

 In the periodic table, Group – 2 elements are called alkaline earth metals, and Group 18 elements are called Noble gases. So, in the 3^rd period, the Group 2 element is Magnesium, and the Group 18 element is Argon. Thus, the Alkaline Earth metal is Magnesium (symbol- Mg), and the Noble gas element is Argon (symbol – Ar).

Step 3: Identify the noble gas

The number of protons corresponds to the atomic number. So, 25 protons correspond to the element Manganese (Mn), with 30 neutrons. It is in the 4^th period in the periodic table, and the noble gas in the same row is Krypton. Thus, the element is Krypton (symbol – Kr)

Step 4: Identify the noble gas

The atomic number of Gold (Au) is 79. It is placed in the 6^th period and 11^th row in the periodic table. Thus, the noble gas element is Radon (Symbol – Rn).