Question

practice

1. fill in the following table with the correct information.

atom/element	atomic #	# of protons	# of neutrons	mass #
hydrogen-2
helium-3
helium-4

Explanation:

Step1: Recall atomic number concept

The atomic number is equal to the number of protons and is unique for each element. Hydrogen has an atomic number of 1 and helium has an atomic number of 2.

Step2: Recall mass - number formula

The mass number ($A$) is the sum of the number of protons ($p$) and neutrons ($n$), i.e., $A=p + n$.

Step3: Calculate for Hydrogen - 1

Atomic number of hydrogen is 1. For Hydrogen - 1, number of protons = 1. Since mass number = 1, number of neutrons = mass number - number of protons = 1 - 1=0.

Step4: Calculate for Hydrogen - 2

Atomic number of hydrogen is 1. For Hydrogen - 2, number of protons = 1. Since mass number = 2, number of neutrons = mass number - number of protons = 2 - 1 = 1.

Step5: Calculate for Helium - 3

Atomic number of helium is 2. For Helium - 3, number of protons = 2. Since mass number = 3, number of neutrons = mass number - number of protons = 3 - 2 = 1.

Step6: Calculate for Helium - 4

Atomic number of helium is 2. For Helium - 4, number of protons = 2. Since mass number = 4, number of neutrons = mass number - number of protons = 4 - 2 = 2.

Atom/Element	Atomic #	# of Protons	# of Neutrons	Mass #
Hydrogen - 2	1	1	1	2
Helium - 3	2	2	1	3
Helium - 4	2	2	2	4

Answer:

Atom/Element	Atomic #	# of Protons	# of Neutrons	Mass #
Hydrogen - 2	1	1	1	2
Helium - 3	2	2	1	3
Helium - 4	2	2	2	4