Question

an atomic physicist determines that an atom is composed of 8 positively charged particles and has a mass of 15 amu. which is the best conclusion that can be drawn? the atom has 7 neutrons and 8 protons. the atom has 7 electrons and 8 protons. the atom has 8 neutrons and 7 electrons. the atom has 8 electrons and 7 protons.

Explanation:

Step1: Recall particle - charge and mass facts

Protons are positively - charged particles. Given 8 positively - charged particles, so number of protons \(p = 8\).

Step2: Use mass - number formula

The mass number \(A\) of an atom is the sum of protons and neutrons (\(A=p + n\)). Given \(A = 15\) and \(p = 8\), then \(n=A - p\). So \(n=15 - 8=7\). Electrons have negligible mass compared to protons and neutrons and are not considered in mass - number calculations.

Answer:

The atom has 7 neutrons and 8 protons.