Examine the three isotopes of potassium (k) below.
potassium-41, potassium-39, potassium-40
which answer choice lists these isotopes in the order of having the least amount of neutrons to having the most amount of neutrons?
potassium-41, potassium-39, potassium-40
potassium-39, potassium-41, potassium-40
potassium-39, potassium-40, potassium-41
potassium-41, potassium-40, potassium-39

The correct answer is Potassium-39, Potassium-40, Potassium-41

Explanation:

Atomic number is defined as the number of protons present in an atom.

Mass number is defined as the sum of number of protons and number of neutrons present in an atom. It is represented as A.

A = Mass number = Number of neutrons + Number of protons.

For the given isotopes of potassium:

Atomic number of potassium is 19.

For potassium-41 isotope:

Mass number = 41

Number of neutrons = 41 - 19 = 22

For potassium-39 isotope:

Mass number = 39

Number of neutrons = 39 - 19 = 20

For potassium-40 isotope:

Mass number = 40

Number of neutrons = 40 - 19 = 21

The most number of neutrons are in potassium-41 isotope and the least number of neutrons are in potassium-39

Hence, the correct answer is Potassium-39, Potassium-40, Potassium-41

it is a good conductor

explanation:

given:

mass of na = 115 g

excess cl2

to determine:

mass of nacl produced

explanation:

given reaction is-

2na(s) + cl2(g) → 2nacl(s)

since cl2 is in excess, na will be the limiting reagent

as per the reaction stoichiometry na: nacl = 1: 1

i.e. moles of na reacted = moles of nacl formed

now, # moles of na = mass of na/atomic mass

                                  = 115 g/23 g.mol-1 = 5 moles

therefore, moles of nacl = 5

molar mass of nacl = 58 g/mol

mass of nacl = 5 moles * 58 g.mol-1 = 290 g

ans: amount of nacl produced = 290 g