2.2 Isotopes Flashcards
(19 cards)
What is a relative atomic mass unit (amu or u)?
A relative atomic mass unit (also called atomic mass unit or amu/u) is a unit used to express the mass of atoms and subatomic particles.
It is defined as 1/12 the mass of a carbon-12 atom.
Which element is used as a standard for relative atomic mass?
Carbon-12 is used as the standard.
1 atomic mass unit (amu) is defined as 1/12 the mass of a carbon-12 atom.
What is the unit of relative atomic mass?
Relative atomic mass has no unit.
How do you write atomic notation using mass number and atomic number?
Atomic notation shows an element’s symbol with its mass number (A) and atomic number (Z):
z
X
A
A = mass number (protons + neutrons)
Z = atomic number (protons)
X = chemical symbol
What is the definition of an isotope?
Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons.
Why do isotopes of the same element have the same chemical properties?
Isotopes have the same number of electrons and thus the same electron configuration, which gives them identical chemical properties. It is the number of electrons in an atom that determines the way in which it forms bonds and reacts with other atoms.
What is the difference between isotopes of the same element?
They have different numbers of neutrons.
What stays the same in all isotopes of an element?
The number of protons and electrons.
Why do some physical properties of isotopes differ?
Because their atomic masses are different.
Which physical properties can differ between isotopes?
Mass, density, and rate of diffusion.
Do isotopes have the same chemical or physical properties?
They have the same chemical properties but may have different physical properties.
What are radioisotopes?
Isotopes with unstable nuclei that spontaneously break apart and emit radiation.
What causes radioisotopes to be unstable?
An imbalance of neutrons and protons in their nuclei.
Give two examples of radioisotopes.
Tritium and carbon-14.
Why are relative atomic masses often not whole numbers?
Because they are averages of the masses of different isotopes.
What is the relative atomic mass (Ar)?
The average mass of all the naturally occurring isotopes of an element, based on their abundances.
Why is chlorine’s relative atomic mass 35.5?
Because it is a mix of Cl-35 and Cl-37 in a 3:1 ratio, making the average 35.5.
