Question

storyline 1 exam
a mystery element has 18 protons. which one of the following statements is true about the element?
the element belongs in row 5 of the periodic table and is classified as an alkaline earth metal.
the element belongs in row 4 of the periodic table and is classified as an alkali metal.
the element belongs in row 2 of the periodic table and is classified as a halogen.
the element belongs in row 3 of the periodic table and is classified as a noble gas.

Explanation:

Step1: Determine the element

The number of protons in an atom is equal to its atomic number. So, the element with 18 protons is Argon (Ar).

Step2: Locate the element in the periodic table

Argon is in row 3 (period 3) of the periodic table.

Step3: Classify the element

Argon is a noble gas.

Answer:

The element belongs in row 3 of the periodic table and is classified as a noble gas.