Question

Part 2: Determine the number of protons, electrons, and neutrons present in an atom of potassium (K). Explain how you determined your answer using complete sentences.

Answer 1

STEPS:

1) NUMBER OF PROTONS: The number of protons is always the same as the element's atomic number. So, since Potassium's atomic number is 19, Potassium has 19 protons.

2) NUMBER OF ELECTRONS: In neutral atoms, the number of electrons is always the same as the number of protons. So (unless it was specified that this atom is an ion), Potassium has 19 electrons.

3) NUMBER OF NEUTRONS: The number of neutrons is the element's mass number (rounded from the average atomic mass) minus the number of protons. So do the math:
               39-19 = 20
So Potassium has 20 neutrons.

Answer 2

Well first we can look at the periodic table and understand what the numbers mean. 
First we look at the top right of the element (AkA) The atomic number which indicates how many protons are in the single nucleus of a single potassium atom, In this case its 19.
Then there Is another number under neath the element that is used to calculate the number of neutron's that are in a single potassium atom. This number is called the atomic weight, In this case the number is 39.098.
First the number is rounded and since the number is in the tenths place we round it downs (No larger than 5) to 39 then we subtract the atomic number to get the typical amount of neutrons in a typical potassium atom: 20

Hope it helps :)