4.17 Mass Number

An atom of mercury contains 120 neutrons in its nucleus and 80 electrons around it. It contains _____ protons in its nucleus and its atomic number is _____.

80, 80

The atomic weight for elements is first determined by John...

Dalton

What is the mass number?

Defined as the number of protons and neutrons in an atom; can be calculated by adding the number of neutrons and the number of protons (atomic number) together

For Mg(2+), if the mass number is 24, the number of neutrons will be 2.

FALSE

For chlorine, the number of neutrons is 17.

FALSE

The atomic number is placed as a superscript of the chemical symbol.

FALSE

The mass number of an atom is the sum total of its electrons and protons.

FALSE

If the sulfur atom has a mass number of 32 and 16 protons, how many electrons and neutrons does it have?

16, 16

A sodium atom has 11 protons and 12 neutrons. What is the mass number of this sodium atom?

23

The atomic number of an element is 22 while its mass number is 48. How many neutrons does the element have?

26

An aluminum atom has 13 protons and 14 neutrons. What is the mass number of this aluminum atom?

27

Who discovered a number of atomic weights (originally based on a comparison to hydrogen) of elements in the early 1800's?

John Dalton

The number of neutrons is used to calculate the _____ number of an atom.

Mass

The number of protons plus the number of neutrons is called the _____ of an atom.

Mass number

Atoms always have the same number of protons and electrons.

TRUE

In a nuclear symbol, the mass number is placed as a superscript before the chemical symbol.

TRUE

The original atomic weights is based on the comparison of hydrogen.

TRUE

An oxygen atom has 8 protons and 8 neutrons. What is the mass number of this oxygen atom?

16

How do you calculate mass number?

(Mass # = # of p(+) + # of n (0))

Sodium has an atomic number of 11 and a mass number of 23. Which of the following are the correct number of protons, neutrons, and electrons, respectively, in a neutral sodium atom?

11, 12, 11

A carbon atom has 6 protons and 6 neutrons. What is the mass number of this carbon atom?

12

A nitrogen atom has 7 protons and 7 neutrons. Which of the following is the correct mass number of this nitrogen atom?

14

You will need to obtain a periodic table. Given the atomic notation of 64/30 Zn, indicate the number of protons, neutrons and electrons respectively, in an atom of zinc.

30, 34, 30

A chlorine atom has 17 protons and 18 neutrons. What is the mass number of this chlorine atom?

35

An element has an atomic number of 35 and a mass number of 80. Which of the following is the correct symbol of the element?

35/Br/80

Which of the following is incorrect?

40/17 Ar (supposed to be 18 protons/atomic number not 17)

The element krypton has an atomic number of 36 and a mass number of 84. How many neutrons in a krypton atom?

48

What is the mass number of a cobalt atom that has 27 protons and 30 neutrons?

57

The atomic notation for a particular atom of boron is 11/5 B. The atomic number is ____, while the mass number is ____.

5; 11

A tin atom has an atomic number of 50 and a mass number of 118. How many neutrons are present in this atom?

68