CSS - PMS - CCE - PCS - General Science
Atomic Structure - Mass Number
An atom has 6 protons and 8 neutrons. What is its mass number?
A. 6
B. 2
C. 14
D. 8
Correct Answer: C
Mass number = 6 + 8 = 14.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Mass Number
Which symbol is commonly used for mass number?
A. pH
B. Z
C. e
D. A
Correct Answer: D
Nuclear notation typically uses A for mass number and Z for atomic number.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Mass Number
What is the mass number of an atom?
A. Number of electron shells
B. Total number of protons and neutrons in its nucleus
C. Number of electrons only
D. Number of protons only
Correct Answer: B
Mass number A equals protons plus neutrons.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Electrons
Which process involves sharing valence electrons between atoms?
A. Radioactive decay only
B. Neutron capture only
C. Nuclear fission
D. Covalent bonding
Correct Answer: D
Covalent bonds form when atoms share pairs of valence electrons.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Electrons
Which quantum number primarily identifies an electron's main energy level?
A. Atomic mass number
B. Oxidation number only
C. Principal quantum number
D. Avogadro number
Correct Answer: C
The principal quantum number n labels the main electron shell or energy level.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Electrons
Which scientist's experiments are associated with determining the electron's charge-to-mass ratio?
A. Niels Bohr only for radioactivity
B. James Chadwick
C. Ernest Rutherford only for neutron discovery
D. J. J. Thomson
Correct Answer: D
J. J. Thomson's cathode-ray experiments established the electron and measured its charge-to-mass ratio.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Electrons
Which subatomic particle has a mass much smaller than that of a proton?
A. Electron
B. Neutron
C. Alpha particle
D. Nucleus
Correct Answer: A
The electron's mass is about 1/1836 of the proton mass.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Electrons
What happens when a neutral atom loses an electron?
A. It becomes an isotope automatically
B. It becomes a neutron
C. Its atomic number becomes zero
D. It becomes a positively charged ion
Correct Answer: D
Loss of electrons leaves more protons than electrons, producing a cation.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Electrons
What happens when a neutral atom gains an electron?
A. It becomes a neutron
B. It becomes a negatively charged ion
C. Its nucleus disappears
D. It becomes a proton
Correct Answer: B
Gaining one or more electrons gives an atom a net negative charge, forming an anion.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Electrons
A neutral atom has equal numbers of electrons and which particles?
A. Photons
B. Neutrons
C. Protons
D. Isotopes
Correct Answer: C
Equal positive and negative charges make the atom electrically neutral.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Electrons
Which electron group mainly determines an element's chemical bonding behavior?
A. All nucleons equally
B. Valence electrons
C. Nuclear protons only
D. Core neutrons
Correct Answer: B
Valence electrons are the outer electrons involved most directly in bonding and reactions.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Electrons
Where are electrons found in an atom?
A. In the nucleus as heavy particles
B. Only inside neutrons
C. Inside protons
D. In orbitals or electron clouds around the nucleus
Correct Answer: D
Electrons occupy quantum states described by orbitals around the nucleus.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Electrons
What is the electric charge of an electron?
A. Neutral
B. Negative
C. Positive
D. Variable positive only
Correct Answer: B
An electron carries one elementary unit of negative charge.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Atomic Number
What happens to the identity of an element if its number of protons changes?
A. It becomes a different element
B. Only its mass unit changes
C. Only its physical state changes
D. It remains the same element in all cases
Correct Answer: A
Changing proton number changes atomic number and therefore elemental identity.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Atomic Number
Can isotopes of the same element have different atomic numbers?
A. Yes, always
B. Only if they are neutral
C. Only at room temperature
D. No, isotopes of the same element have the same atomic number
Correct Answer: D
Isotopes differ in neutron number, not proton number.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Atomic Number
If a neutral atom has atomic number 11, how many electrons does it have?
A. 12
B. 10
C. 11
D. 22
Correct Answer: C
A neutral atom has the same number of electrons as protons.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Atomic Number
Which symbol is commonly used for atomic number in nuclear notation?
A. N
B. M
C. A
D. Z
Correct Answer: D
In nuclear notation, Z is atomic number and A is mass number.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Atomic Number
If an atom has 8 protons, what is its atomic number?
A. 10
B. 16
C. 4
D. 8
Correct Answer: D
Atomic number equals the number of protons.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Atomic Number
Which quantity uniquely identifies a chemical element?
A. Number of neutrons alone
B. Mass number alone
C. Physical state
D. Atomic number
Correct Answer: D
Each element is defined by its proton number, i.e., its atomic number.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Atomic Number
In a neutral atom, the atomic number is also equal to the number of what particles?
A. Electrons
B. Nucleons only
C. Isotopes
D. Neutrons
Correct Answer: A
A neutral atom has equal numbers of positively charged protons and negatively charged electrons.