Question

the number of protons in an atom is known as its atomic number. atoms that share the same atomic number are classified as the same chemical element. below is a model representing an atom of the chemical element lithium. what is lithiums atomic number? which of the following models also represents a lithium atom?

Explanation:

Step1: Count the number of protons

In the given lithium atom model, count the number of yellow (proton) particles. There are 3 protons.

Step2: Recall the definition of atomic number

Since the atomic number is the number of protons in an atom, and we found 3 protons.

Step3: Analyze the second part (model selection)

For an atom to be lithium, it must have 3 protons. Check each model:

• First model: 3 protons (matches lithium's atomic number).
• Second model: 4 protons (not lithium).
• Third model: 4 protons (not lithium).

Answer:

Lithium's atomic number is \(3\). The first model (with 3 protons) also represents a lithium atom.