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.
CSS - PMS - CCE - PCS - General Science
Atomic Structure - Atomic Number
What does the atomic number of an element represent?
A. Number of electron shells
B. Number of neutrons only
C. Number of protons in the nucleus
D. Total protons plus neutrons
Correct Answer: C
Atomic number Z is defined as the number of protons in the nucleus.