CSS - PMS - CCE - PCS - General Science
Atomic Structure - Protons
Which atomic quantity equals the number of protons?
A. Neutron number
B. Number of isotopes
C. Atomic number
D. Mass number always
Correct Answer: C
Atomic number Z is defined by proton count.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Protons
Where are protons located in an atom?
A. In electron shells
B. In the nucleus
C. Inside molecules but not atoms
D. Outside the atom only
Correct Answer: B
Protons are nucleons located in the atomic nucleus.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Protons
What is the electric charge of a proton?
A. Neutral
B. Positive
C. Negative
D. Variable only
Correct Answer: B
A proton carries one elementary unit of positive charge.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Neutrons
Which isotope of hydrogen contains two neutrons?
A. Protium
B. Tritium
C. Deuterium
D. Hydrogen-0
Correct Answer: B
Tritium has one proton and two neutrons.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Neutrons
Which isotope of hydrogen contains one neutron?
A. Tritium has one neutron
B. Deuterium
C. Protium
D. Helium-3
Correct Answer: B
Deuterium has one proton and one neutron.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Neutrons
A hydrogen-1 nucleus contains how many neutrons?
A. 2
B. 1
C. 3
D. 0
Correct Answer: D
Ordinary hydrogen (protium) has one proton and no neutrons.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Neutrons
Which subatomic particle has a mass slightly greater than that of a proton?
A. Electron
B. Neutron
C. Positron
D. Photon
Correct Answer: B
The neutron is slightly more massive than the proton.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Neutrons
Which force helps bind protons and neutrons together in the nucleus?
A. Frictional force
B. Strong nuclear force
C. Centrifugal force only
D. Buoyant force
Correct Answer: B
At very short nuclear distances, the strong interaction binds nucleons.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Neutrons
What mainly differs among isotopes of the same element?
A. Number of neutrons
B. Chemical symbol
C. Number of protons
D. Atomic number
Correct Answer: A
Isotopes have the same proton number but different neutron numbers.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Neutrons
How is neutron number calculated from mass number A and atomic number Z?
A. A × Z
B. A + Z
C. A − Z
D. Z − A
Correct Answer: C
Since mass number is protons plus neutrons and atomic number is protons, N = A − Z.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Neutrons
Who is credited with the discovery of the neutron in 1932?
A. James Chadwick
B. Michael Faraday
C. J. J. Thomson
D. Robert Hooke
Correct Answer: A
James Chadwick demonstrated the existence of the neutron in 1932.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Neutrons
Where are neutrons located in an atom?
A. Inside photons
B. Outside the atom only
C. In the nucleus
D. In electron shells only
Correct Answer: C
Neutrons, together with protons, form the atomic nucleus.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Neutrons
What is the electric charge of a neutron?
A. Zero
B. Negative
C. Positive
D. Double positive
Correct Answer: A
A neutron is electrically neutral.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Mass Number
Which quantity should not be confused with relative atomic mass?
A. Melting point only
B. State of matter
C. Mass number of a specific nuclide
D. Chemical symbol
Correct Answer: C
Mass number is an integer for one nuclide, whereas relative atomic mass is a weighted average over naturally occurring isotopes.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Mass Number
Can two different elements have the same mass number?
A. No, mass number uniquely defines an element
B. Only at high temperature
C. Yes, such nuclides are called isobars
D. Only if both are hydrogen
Correct Answer: C
Different elements can have the same mass number but different atomic numbers; these are isobars.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Mass Number
If A = 23 and Z = 11, how many neutrons are present?
A. 11
B. 34
C. 23
D. 12
Correct Answer: D
Neutrons = A − Z = 23 − 11 = 12.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Mass Number
An isotope is written as carbon-14. What does 14 represent?
A. Number of electron shells
B. Atomic number
C. Valency
D. Mass number
Correct Answer: D
The number following an element name in isotope notation usually gives the mass number.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Mass Number
Which particles contribute approximately one atomic mass unit each to mass number?
A. Protons and neutrons
B. Electrons only
C. Electrons and photons
D. Photons and neutrinos
Correct Answer: A
Protons and neutrons are nucleons and each has a mass close to 1 u.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Mass Number
Do isotopes of the same element necessarily have the same mass number?
A. Only if ionized
B. No
C. Yes, always
D. Only in gases
Correct Answer: B
Isotopes have the same proton number but different neutron numbers, so their mass numbers differ.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Mass Number
How can the number of neutrons be found if mass number and atomic number are known?
A. Atomic number divided by mass number
B. Atomic number squared
C. Mass number minus atomic number
D. Mass number plus atomic number
Correct Answer: C
N = A − Z because A = protons + neutrons and Z = protons.