Question

The first model represents the proton and neutron distribution in the nucleus of four helium isotopes. The second image shows the entry for helium in the periodic table. Based on the information in the periodic table, which is the most common isotope of helium?

Answer 1

Answer: B

Step-by-step explanation:

Isotopes are elements which have same atomic number but different mass number.

General representation of an element is given as:
`_Z^A\textrm{X}`

where,

Z represents Atomic number

A represents Mass number

X represents the symbol of an element

Thus for helium , which is shown to be
`_2^4\textrm{He}`

Mass number is defined as the sum of number of protons and neutrons that are present in an atom.

Mass number = Number of protons + Number of neutrons = 4

Number of neutrons = 4-2 =2

Atomic number is defined as the number of protons or number of electrons that are present in an atom.

Atomic number = Number of electrons = Number of protons = 2

Thus the representation with 2 protons and 2 neutrons will be the most common isotope of helium.

Answer 2

The correct option is B.
Helium exist as an isotope, its most common isotope is the one that is placed on the periodic table. The helium atom on the periodic table has two electrons, two protons and two neutrons. The proton and the neutron are located inside the nucleus, this means that two protons and two neutrons can be found inside the helium nucleus. Thus, in the pictures given above, the correct picture is the one that contain four particles.