Question 21

Question

A student looks up an element on the periodic table. The table says that the atomic number of the element is 12 and the mass number of the element is 40. What information do these two numbers convey about the element?

a
The element has 40 protons and 12 neutrons
b
The element has 12 protons and 12 neutrons
c
The element has 12 protons and has 28 neutrons
d
The element has 28 protons and 40 neutrons
Question 22
In all elements in a group, the thing that is the same is the:

a
Number of electrons in the valence shell
b
Number of electrons
c
Number of protons
d
Number of neutrons

Answer 1

Question 21:
To determine the number of protons and neutrons in the element, we use the following definitions:

• The atomic number (12) indicates the number of protons in the atom.
• The mass number (40) is the sum of the number of protons and neutrons.

To find the number of neutrons, we subtract the atomic number from the mass number: \[ \text{Neutrons} = \text{Mass Number} - \text{Atomic Number} = 40 - 12 = 28 \]

So, the element has 12 protons and 28 neutrons. The correct answer is: c The element has 12 protons and has 28 neutrons.

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Question 22:
In any group of the periodic table, elements share similar chemical properties due to having the same number of valence electrons. Therefore, the correct answer is: a Number of electrons in the valence shell.