Chemistry Quiz - 11th Grade TO 1

An atom of magnesium has a mass number of 24 and an atomic number of 12. Which statement about this atom is correct?

• It contains 24 protons, 24 neutrons, and 24 electrons.

• It contains 24 protons, 12 neutrons, and 24 electrons.

• It contains 12 protons, 24 neutrons, and 12 electrons.

• It contains 12 protons, 12 neutrons, and 12 electrons.

• It contains 12 protons, 11 neutrons, and 12 electrons.

Two neutral atoms, M and N, have the following characteristics: • Atom M: 8 protons, 8 electrons, 8 neutrons • Atom N: 7 protons, 7 electrons, 8 neutrons Which of the following statements is correct?

• M and N are isotopes because they have the same number of protons but different neutrons.

• M and N are isotones because they have the same number of neutrons but different protons.

• M and N are isobars because they have the same mass number but different atomic numbers.

• M and N are isotopes because they have the same number of neutrons but different protons.

• M and N are isotopes because they have the same mass number but different neutrons

The relative atomic mass of bromine is 79.9. Which statement best explains this value?

• Bromine atoms contain 79 protons and 0.9 neutrons.

• Bromine consists only of the isotope 3580Br

• Bromine consists only of the isotope 3579Br

• Bromine has two major isotopes with mass numbers 79 and 81 that exist in unequal abundance.

• Bromine atoms each have a fractional number of nucleons.

Several species are listed below. Analyze them and determine which one represents a particle that has the same number of protons as a calcium atom, but a different number of electrons.

• ²⁰₄₀Ca

• ³⁹₁₉K⁺

• ²⁰₄₀Ca²⁺

• ²¹₄₅Sc

• ¹⁸₃₆Ar

Which statement best explains the Pauli exclusion principle?

• No two electrons in an atom can have the same set of four quantum numbers

• Electrons fill orbitals starting with the lowest energy first

• Electrons are added one at a time to degenerate orbitals before pairing

• Electrons travel around the nucleus in fixed circular orbits

• Electrons always pair with parallel spins

Which observation best explains the existence of neutrons in the nucleus?

• Mass number of atoms being greater than the number of protons

• Deflection of alpha particles in Rutherford's experiment

• Discovery of isotopes having different electron numbers

• Continuous spectrum observed from heated elements

• Observation of metallic bonding strength

An unknown element Z has electron configuration 2,8,7. Identify the element and its atomic number. Predict its position in the periodic table (period and group). Explain whether it is more likely to form covalent or ionic bonds, and justify your answer using its configuration. Suggest two different compounds it can form (one ionic and one covalent).

• Z = Chlorine (Z = 17); Period 3, Group 17; forms ionic (NaCl) and covalent (HCl).

• Z = Fluorine (Z = 9); Period 2, Group 17; forms ionic (KF) and covalent (HF).

• Z = Bromine (Z = 35); Period 4, Group 17; forms ionic (KBr) and covalent (HBr).

• Z = Oxygen (Z = 8); Period 2, Group 16; forms covalent (H₂O).

• Z = Nitrogen (Z = 7); Period 2, Group 15; forms covalent (NH₃).

Which subatomic particle is primarily responsible for the chemical properties of an atom?

• Proton

• Neutron

• Electron in the outermost shell

• Nucleon

• Electron in the inner shells

An element has the electronic configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹. Which statement best explains its position in the periodic table?

• Group 2, Period 4

• Group 1, Period 3

• Group 1, Period 4

• Group 2, Period 3

• Group 13, Period 4

Arrange the following ions in order of increasing ionic radius: O²⁻, F⁻, Na⁺, Mg²⁺, Al³⁺. Which sequence is correct?

• Al³⁺ < Mg²⁺ < Na⁺ < F⁻ < O²⁻

• O²⁻ < F⁻ < Na⁺ < Mg²⁺ < Al³⁺

• Na⁺ < Mg²⁺ < Al³⁺ < F⁻ < O²⁻

• Al³⁺ < Na⁺ < Mg²⁺ < O²⁻ < F⁻

• Mg²⁺ < Al³⁺ < Na⁺ < F⁻ < O²⁻