protons neutrons number number (symbol) 20 20 a b c 9 d e 19 f using the periodic table, complete the table…

Explanation:

Step1: Recall atomic number definition

Atomic number = number of protons. For the first - row atom with 20 protons, the atomic number (A) is 20.

Step2: Recall mass number definition

Mass number = number of protons + number of neutrons. For the first - row atom with 20 protons and 20 neutrons, the mass number (B) is (20 + 20=40).

Step3: Identify element by atomic number

The element with atomic number 20 is calcium, and its symbol (C) is Ca.

Step4: Calculate neutrons for second - row atom

For the second - row atom with atomic number (number of protons) 9 and mass number 19, the number of neutrons (D) is (19−9 = 10).

Step5: Determine atomic number for second - row atom

The atomic number (E) is equal to the number of protons, so E = 9.

Step6: Identify element by atomic number

The element with atomic number 9 is fluorine, and its symbol (F) is F.

Answer:

A. 20 B. 40 C. Ca D. 10 E. 9 F. F