Atomic Structure Set 2

65

An isotope of copper contains 29 electrons, 29 protons, and 36 neutrons. What is the mass number of this isotope?

236

An isotope of uranium contains 92 electrons and 144 neutrons. What is the mass number of this isotope?

Isotopes

Atoms of an element with different numbers of neutrons care called ________.

Atomic mass is a weighted average of the masses of all isotopes of an atom. Nitrogen's atomic mass is 14.007. This means that isotope N-14 is the most abundant because the average is significantly closer to 14.

Challenge: Nitrogen has two naturally occurring isotopes, N-14 and N-15. Its atomic mass is 14.007. Which isotope is more abundant? Explain your answer.

63.545 amu

Copper has two isotopes: Cu-63 (abundance = 69.2%), mass = 62.930 amu) and Cu-65 (abundance = 30.8%, mass = 64.928 amu). Calculate the atomic mass of copper.

1/12th the mass of a carbon-12 atom

How is the atomic mass unit (amu) defined?

20, 20

How many protons and electrons are in an atom of calcium?

31, 31

How many protons and electrons are in an atom of gallium?

42, 42

How many protons and neutrons are in an atom of molybdenum?

Mass number

The ______ of an tom is the sum of its neutrons and protons.

Atomic number

The _________ of an atom is given by its number of protons.

24.305 amu

Three magnesium isotopes have atomic masses and relative abundances of 23.985 amu (78.99%), 24.986 amu (10.00%), and 25.982 amu (11.01%). Calculate the atomic mass of magnesium.

37

What is the atomic number of an atom that contains 37 electrons?

72

What is the atomic number of an atom that contains 72 protons?

atomic number = number of protons = number of electrons

What is true for any atom?

Protons

Which subatomic particle identifies an atom as that of a particular element?

because it is a weighted average of the naturally occurring isotopes of an element

Why are the atomic masses of the elements not whole numbers?