Atomic Structure
What subatomic particle has a positive charge?
What is a proton?
What is an isotope?
What is isotopes are versions of the same element that differ in the number of neutrons.
Why does the average atomic mass of an element usually have a decimal?
What is because it is a weighted average of isotopes, not a single whole number.
One atom has 6 protons and 6 neutrons, another has 6 protons and 8 neutrons. Are these the same element? Explain why or why not.
What is yes, both are carbon because they have the same number of protons. They are different isotopes (C-12 and C-14) because they have different numbers of neutrons.
Define “proton” and give an example.
What is a positively charged particle in the nucleus?
How many protons, neutrons, and electrons are in a neutral ⁴He atom?
What is:
Protons: 2, Neutrons: 2, Electrons: 2
How many neutrons are in ⁵⁶Fe?
What is 30 neutrons (56 − 26 = 30)
An element has isotopes A-23 (mass = 23 u, abundance = 60%) and A-24 (mass = 24 u, abundance = 40%). Calculate the average atomic mass.
What is 23.4 amu?
An atom has 11 protons and 12 neutrons. Identify the element and its mass number
What is Sodium (Na), Mass number = 11 + 12 = 23
Define “electron.”
What is a negatively charged particle orbiting the nucleus
For a neutral atom of ²⁷Al, identify the number of protons, neutrons, and electrons. Then explain why the atom is electrically neutral.
What is
Protons: 13, Neutrons: 14, Electrons: 13
Explanation: The atom is neutral because the number of electrons equals the number of protons, balancing the positive and negative charges.
Write the isotope symbol for an atom with 8 protons and 8 neutrons.
What is ¹⁶O?
Argon has isotopes 36, 38, and 40. Which is most abundant if average = 39.948?
What is Argon-40 (because the average is closest to 40)?
One atom has 8 protons & mass 16; another has 8 protons & mass 17. Identify the element and explain the difference in mass numbers.
What is both are oxygen? The difference in mass numbers is due to differing numbers of neutrons (O-16 has 8 neutrons, O-17 has 9 neutrons).
Give an example of isotopes.
What is versions of the same element with different neutrons; e.g., C-12 and C-14?
Explain why the number of protons defines the element.
What is the number of protons (atomic number) determines the element’s identity; each element has a unique number of protons.
Compare C-12 and C-14 in terms of protons and neutrons.
What is both have 6 protons; C-12 has 6 neutrons, C-14 has 8 neutrons?
If an element has two isotopes, one very rare and one very common, will the average atomic mass be closer to the rare isotope or the common isotope? Explain.
What is it will be closer to the common isotope because the weighted average favors the more abundant isotope?
Explain the difference between atomic mass and atomic weight.
What is atomic mass is the mass of a single atom (protons + neutrons); atomic weight (or average atomic mass) is the weighted average of all isotopes in nature.
Define “average atomic mass.”
What is a weighted average of all naturally occurring isotopes of an element?
Describe the difference between mass number and atomic number.
What is:
Atomic number = number of protons; Mass number = protons + neutrons
Two isotopes of an element are ¹⁰B and ¹¹B. Which isotope would be more common if the element’s average atomic mass is 10.81 amu? Explain your reasoning.
What is the more common isotope is ¹¹B because the average atomic mass (10.81 amu) is closer to 11 than 10?
An element has two isotopes: A-10 (30% abundance) and A-11 (70% abundance). Without calculating, explain whether the average atomic mass will be closer to 10 or 11 and why.
What is the average atomic mass will be closer to 11 because the more abundant isotope (A-11) has a greater influence in the weighted average?
Solve: Sample contains 75% Cl-35 and 25% Cl-37. Calculate average atomic mass.
What is 35.5 amu?
Define “atomic number” and explain its significance.
What is the number of protons in an atom; defines the element’s identity