what is heliums atomic number? which of the following models also represents a helium atom?
what is heliums atomic number? which of the following models also represents a helium atom?
Answer
Explanation:
Step1: Recall atomic number definition
The atomic number is equal to the number of protons in an atom.
Step2: Count protons in helium
In the given helium - atom model, there are 2 protons. So the atomic number of helium is 2.
Step3: Identify correct helium - atom model
A helium atom has 2 protons, 2 neutrons (usually), and 2 electrons. The correct model should have 2 protons in the nucleus, 2 neutrons in the nucleus, and 2 electrons in the electron - shell. The third model from the left has 2 protons, 2 neutrons in the nucleus and 2 electrons in the electron - shell.
Answer:
The atomic number of helium is 2. The model that represents a helium atom is the third one from the left.