Question

What can be inferred from the symbol ${}_2^{4}He$?

• A. An atom of helium contains two electrons
• B. An atom of helium has two protons and four neutrons in its nucleus
• C. The proton (atomic) number of helium is four
• D. Helium acts as a diatomic molecule

Answer 1

The correct option is A An atom of helium contains two electrons

${}_2^{4}He$

Here, $Z=$ atomic number $=$number of protons $=$ $2$

$A=$ mass number $=$ number of protons $+$ number of neutrons $=4$

Therefore, Number of protons $=$ Number of electrons $=2$

Number of neutrons $=$ $A-Z=4-2=2$