,Question 1
An atom has 17 protons, 18 electrons and 18 neutrons.
Which statement correctly identifies the particle?
A. A neutral chlorine atom
B. A chloride ion
C. An argon atom
D. A chlorine isotope with no charge
Correct answer: B
Rationale:
17 protons identifies the element as chlorine. Having 18 electrons means the particle has
gained one electron and therefore has a −1 charge. It is a chloride ion, Cl⁻.
Question 2
Two atoms of the same element have mass numbers 35 and 37.
Which statement is correct?
A. They have different numbers of protons.
B. They have different numbers of electrons.
C. They have different numbers of neutrons.
D. They are different elements.
Correct answer: C
Rationale:
Isotopes have the same number of protons but different numbers of neutrons. Chlorine-35
has 18 neutrons, while chlorine-37 has 20 neutrons.
Question 3
An element has the electronic structure 2,8,7.
Which statement is most likely to be correct?
,A. It is a Group 1 metal.
B. It is a Group 7 non-metal.
C. It is a Group 0 noble gas.
D. It is a transition metal.
Correct answer: B
Rationale:
The atom has seven electrons in its outer shell, placing it in Group 7. Group 7 elements are
halogens and are non-metals.
Question 4
An atom has 2 electrons in its first shell and 8 electrons in its second shell.
What is the most likely charge of the ion formed by an element with this structure if it is in
Group 1?
A. +1
B. −1
C. +2
D. −2
Correct answer: A
Rationale:
Group 1 elements have one electron in their outer shell. They tend to lose this electron to
form a +1 ion.
Question 5
Why did Mendeleev leave gaps in his periodic table?
A. He believed atoms could not exist in those positions.
B. He predicted that undiscovered elements would fit those gaps.
C. He did not know the atomic masses of any elements.
D. He wanted all elements to have the same properties.
Correct answer: B
Rationale:
Mendeleev deliberately left gaps for elements that had not yet been discovered. Some later-
discovered elements had properties close to his predictions, supporting his approach.
, Question 6
An element reacts vigorously with water and forms a +1 ion.
Which group is it most likely to belong to?
A. Group 0
B. Group 1
C. Group 7
D. Group 8
Correct answer: B
Rationale:
Group 1 metals lose one outer electron and form +1 ions. They are also known for reacting
with water, with reactivity increasing down the group.
Question 7
Which statement explains why elements in the same group have similar chemical properties?
A. They have the same number of protons.
B. They have the same number of electron shells.
C. They have the same number of electrons in their outer shell.
D. They have the same relative atomic mass.
Correct answer: C
Rationale:
Chemical reactions involve the outer electrons. Elements in the same group have the same
number of outer-shell electrons, giving them similar chemical properties.
Question 8
A sodium atom becomes a sodium ion.
Which change occurs?
A. It gains one proton.
B. It loses one proton.
An atom has 17 protons, 18 electrons and 18 neutrons.
Which statement correctly identifies the particle?
A. A neutral chlorine atom
B. A chloride ion
C. An argon atom
D. A chlorine isotope with no charge
Correct answer: B
Rationale:
17 protons identifies the element as chlorine. Having 18 electrons means the particle has
gained one electron and therefore has a −1 charge. It is a chloride ion, Cl⁻.
Question 2
Two atoms of the same element have mass numbers 35 and 37.
Which statement is correct?
A. They have different numbers of protons.
B. They have different numbers of electrons.
C. They have different numbers of neutrons.
D. They are different elements.
Correct answer: C
Rationale:
Isotopes have the same number of protons but different numbers of neutrons. Chlorine-35
has 18 neutrons, while chlorine-37 has 20 neutrons.
Question 3
An element has the electronic structure 2,8,7.
Which statement is most likely to be correct?
,A. It is a Group 1 metal.
B. It is a Group 7 non-metal.
C. It is a Group 0 noble gas.
D. It is a transition metal.
Correct answer: B
Rationale:
The atom has seven electrons in its outer shell, placing it in Group 7. Group 7 elements are
halogens and are non-metals.
Question 4
An atom has 2 electrons in its first shell and 8 electrons in its second shell.
What is the most likely charge of the ion formed by an element with this structure if it is in
Group 1?
A. +1
B. −1
C. +2
D. −2
Correct answer: A
Rationale:
Group 1 elements have one electron in their outer shell. They tend to lose this electron to
form a +1 ion.
Question 5
Why did Mendeleev leave gaps in his periodic table?
A. He believed atoms could not exist in those positions.
B. He predicted that undiscovered elements would fit those gaps.
C. He did not know the atomic masses of any elements.
D. He wanted all elements to have the same properties.
Correct answer: B
Rationale:
Mendeleev deliberately left gaps for elements that had not yet been discovered. Some later-
discovered elements had properties close to his predictions, supporting his approach.
, Question 6
An element reacts vigorously with water and forms a +1 ion.
Which group is it most likely to belong to?
A. Group 0
B. Group 1
C. Group 7
D. Group 8
Correct answer: B
Rationale:
Group 1 metals lose one outer electron and form +1 ions. They are also known for reacting
with water, with reactivity increasing down the group.
Question 7
Which statement explains why elements in the same group have similar chemical properties?
A. They have the same number of protons.
B. They have the same number of electron shells.
C. They have the same number of electrons in their outer shell.
D. They have the same relative atomic mass.
Correct answer: C
Rationale:
Chemical reactions involve the outer electrons. Elements in the same group have the same
number of outer-shell electrons, giving them similar chemical properties.
Question 8
A sodium atom becomes a sodium ion.
Which change occurs?
A. It gains one proton.
B. It loses one proton.
