Answer:
The elements in same period have same principle quantum number or energy shell.
The elements in same group shows similar chemical and properties.
Explanation:
Inn group:
The elements in same group i.e present in vertical column shows similar chemical properties.
The elements in same group having same number of valance electrons. while in chemical reaction bonds are break and formed and valance electrons are involved. That's why elements in same group having same number of valance electrons and shows similar chemical properties.
In period:
While as we move from left to right the number of valance electron increase by one in every element. But the electron is added in same shell which means that their physical and chemical properties are different but principal quantum number is same.
The answer is c hopefully I helped you
I don't know if this is multiple choice but if it isn't I can name of few.
Fun Fact: Noble Metals are chemical elements that have outstanding tolerance and resistance to oxidation.
Answer: Palladium, Silver, Platinum, and Gold. Those are all examples of Noble Metals.
Other: Ruthenium, osmium, and rhodium.
<em>Hope this helps!</em>
Answer:

Explanation:
R = Rydberg constant = 
= Principal quantum number of an energy level = 2
= Principal quantum number of an energy level for the atomic electron transition = 4
Wavelength is given by the Rydberg formula

The wavelength of the light emitted is
.