1.2 - Elements, Isotopes & Relative Atomic Mass

Question 1

What is the mass number of an atom with 13 protons and 14 neutrons?

Answer 1

27

Mass number = Number of protons + Number of neutrons

Question 2

What are isotopes?

Answer 2

Atoms of the same element with different numbers of neutrons

Isotopes have the same atomic number but different mass numbers

Question 3

Which two atoms are isotopes of the same element from the following: Atom W (11 protons, 10 neutrons), Atom X (10 protons, 10 neutrons), Atom Y (9 protons, 9 neutrons), Atom Z (10 protons, 9 neutrons)?

Answer 3

Atom X and Atom Z

They both have 10 protons, making them isotopes of the same element

Question 4

What are the two naturally occurring isotopes of lithium?

Answer 4

Lithium-6 and Lithium-7

Lithium-6 has an abundance of 7.6%, and Lithium-7 has an abundance of 92.4%

Question 5

How many neutrons does Uranium-235 have if it has 92 protons?

Answer 5

143

Neutrons = Mass number - Protons; Uranium-235 has a mass number of 235 and 92 protons

Question 6

What is relative atomic mass

Answer 6

average mass of all the isotopes that make up an element

Question 7

Whats the equation of relative atomic mass?

Answer 7

sum of (isotope abundance x isotope mass)

sum of abundance of all isotopes