Question

concept 2: isotopes

1. which numbers on the periodic table tell you the following information?

a. the number of protons in an element:____________________
b. the number of protons and neutrons in an element:____________________
c. the number of total electrons in an element:____________________
d. the identify of an element:____________________
e. the most common form of an element:____________________

1. explain what it means for an atom to be electrically neutral.

a. ____________________________________________________

1. compare two isotopes of the same element:

a. what do they have in common?____________________
b. what is different about them?____________________
c. when is an isotope considered to be the most stable?____________________
____________________________________________________

1. write the most common isotope for lithium in

a. hyphen notation:____________________
b. nuclear notation:____________________

Explanation:

• 3a: The atomic number represents the number of protons in an element.
• 3b: The mass number is the sum of protons and neutrons in an element.
• 3c: In a neutral atom, the number of electrons equals the number of protons (atomic number).
• 3d: The atomic number uniquely identifies an element.
• 3e: The mass number (as it often corresponds to the most common isotope's proton - neutron sum).
• 4a: An atom is electrically neutral when the number of protons (positive charge) equals the number of electrons (negative charge).
• 5a: Isotopes of the same element have the same number of protons (and electrons in neutral state) and the same atomic number.
• 5b: They have different numbers of neutrons and different mass numbers.
• 5c: An isotope is most stable when the ratio of neutrons to protons is in a certain range (for light elements, close to 1:1; for heavier elements, a bit higher).
• 6a: Lithium - 7 (since lithium - 7 is the most common isotope of lithium).
• 6b: \(_{3}^{7}\text{Li}\) (where 3 is the atomic number and 7 is the mass number).

Answer:

3a. Atomic number
3b. Mass number
3c. Atomic number (in a neutral atom)
3d. Atomic number
3e. Mass number
4a. Number of protons equals number of electrons
5a. Same number of protons (atomic number)
5b. Different number of neutrons (mass number)
5c. When neutron - to - proton ratio is optimal
6a. Lithium - 7
6b. \(_{3}^{7}\text{Li}\)