Question

how many protons, neutrons, and electrons are there in an atom with an atomic number of 55 and a mass of 135? 1 point 55 protons, 80 neutrons, 55 electrons 55 protons, 55 neutrons, 80 electrons 50 protons, 120 neutrons, 75 electrons 80 protons, 70 neutrons, 55 electrons

Explanation:

Step1: Recall atomic structure rules

Atomic number = number of protons = number of electrons (in a neutral atom). Mass number = protons + neutrons.

Step2: Calculate protons, electrons, neutrons

• Atomic number = 55 ⇒ protons = 55, electrons = 55.
• Mass number = 135 ⇒ neutrons = \( 135 - 55 = 80 \).

Step3: Match with options

The first option has 55 protons, 80 neutrons, 55 electrons, which matches the calculations.

Answer:

A. 55 protons, 80 neutrons, 55 electrons