2.3 — isotopes and relative mass

Question 1

what are elements defined as?

Answer 1

substance made up of only one type of atom, where all the atoms of a substance have the same number of protons

Question 2

what are isotopes defined as?

Answer 2

atoms of the same element that have the same number of protons but different numbers of neutrons

Question 3

what causes isotopes to have the same chemical properties (e.g reactivity)?

Answer 3

having the same electron configuration

Question 4

what causes isotopes to have slightly different physical properties (e.g mass and density)?

Answer 4

having varying atomic mass

Question 5

what is the definition of relative atomic mass?

Answer 5

the mass of an atom of an isotope compared to 1/12 the mass of a carbon-12 atom

Question 6

what is the definition of relative atomic mass (Ar)?

Answer 6

the weighted mean mass of an atom of an element compared to 1/12 the mass of a carbon-12 atom

Question 7

what is the definition of relative molecular mass?

Answer 7

the average mean mass of a molecule compared to 1/12 the mass of a carbon-12 atom

Question 8

how is relative atomic mass (Ar) calculated?

Answer 8

the average of the masses of all the isotopes of an element

Question 9

how is relative molecular mass (Mr) calculated?

Answer 9

adding up the relative atomic mass (Ar) values of all the atoms in one molecule

Question 10

what is relative formula mass used for?

Answer 10

ionic compounds

Question 11

how do you calculate relative atomic mass (Ar) from isotopic abundances?

Answer 11

Ar = sum of (isotopic mass x isotopic abundance) / sum of abundance of all isotopes