Question

unit 2: atoms and isotopes
directions: answer each question completely. indicate how you determined the answer to each question below.

1. draw and label the model of atom to show where the protons, neutrons, and electrons can be found.
2. if an isotope of uranium has 92 protons (z = 92) and 143 neutrons, what is the mass number of this isotope?

Explanation:

Step1: Recall mass - number formula

The mass number (A) of an atom is the sum of the number of protons (p) and neutrons (n). The formula is $A=p + n$.

Step2: Identify values of p and n

We are given that the number of protons $p = 92$ and the number of neutrons $n=143$.

Step3: Calculate the mass number

Substitute the values into the formula: $A=92 + 143=235$.

Answer:

235

(Note: For the first - part of drawing the atom model, it is a visual task. A simple way is to draw a small circle in the center to represent the nucleus where protons and neutrons are located. Then draw concentric circles around the nucleus to represent electron - shells and place small dots on the shells to represent electrons.)