Question 1

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 2
In order for an atom to be considered "neutral", which of the following must be true?

a
The number of protons and neutrons must be the same
b
The number of protons and electrons must be the same
c
There are more protons than electrons
d
There are more neutrons than protons
Question 3
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 1:
The atomic number represents the number of protons in an element, while the mass number represents the sum of protons and neutrons. Given that the atomic number is 12, the element has 12 protons. The mass number is 40, so to find the number of neutrons, we subtract the number of protons from the mass number:

Number of neutrons = Mass number - Atomic number = 40 - 12 = 28.

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

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Question 2:
For an atom to be neutral, it must have an equal number of protons and electrons; the neutrons do not affect the charge of the atom.

So the correct option is:
b The number of protons and electrons must be the same.

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Question 3:
Elements in the same group of the periodic table have the same number of electrons in their outermost (valence) shell, which determines their chemical properties.

So the correct option is:
a Number of electrons in the valence shell.