Science 9 Reviewer

In the quantum mechanical model of the atom, which subatomic particle determines the identity of an element?

• Atomic mass

• Number of neutrons

• Number of protons

• Number of orbitals

Rutherford’s gold foil experiment led to the discovery of a dense central region in the atom. Based on this model, which subatomic particle(s) are found in the nucleus?

• Proton and electron

• Neutron and electron

• Proton and neutron

• Proton only

Read each statement and its corresponding reason carefully. Then, analyze the relationship between the two. Choose the correct answer from the options and select the letter of your answer.

Statement A: The energy of an electron in an atom is greater for greater values of n. Statement B: The number, n, is referred to as the principal quantum number.

• A. Both the statement is correct

• B. Both the statement is incorrect

• C. If the first statement is incorrect and the second statement is correct

• D. If the first statement is correct and the second statement is incorrect

Read each statement and its corresponding reason carefully. Then, analyze the relationship between the two. Choose the correct answer from the options and select the letter of your answer.

Statement A: The positively charged protons in the nucleus stabilize the electronic orbitals by electrostatic attraction between the positive charges of the protons and the negative charges of the electrons.

Statement B: The further away the electron is from the nucleus, the lower the energy it has.

• A. Both the statement is correct

• B. Both the statement is incorrect

• C. If the first statement is incorrect and the second statement is correct

• D. If the first statement is correct and the second statement is incorrect

Evaluate the diagram on the right side. Then, analyze the statements. Choose the correct answer from the options and select the letter of your answer.

Statement A: When an electron absorbs energy, it moves to a higher energy level, and the energy change is positive.

Statement B: When an electron falls to a lower energy level, it releases energy, and the energy change is negative.

• A. Both the statement is correct

• B. Both the statement is incorrect

• C. If the first statement is incorrect and the second statement is correct

• D. If the first statement is correct and the second statement is incorrect

Read each statement and its corresponding reason carefully. Then, analyze the relationship between the two. Choose the correct answer from the options and select the letter of your answer.

Statement A: The quantum mechanical model specifies the probability of finding an electron in the three-dimensional space around the nucleus and is based on solutions of the Schrödinger equation.

Statement B: The angular momentum quantum number l is an integer that defines the shape of the orbital and takes on the values l = 0, 1, 2..

• A. Both the statement is correct

• B. Both the statement is incorrect

• C. If the first statement is incorrect and the second statement is correct

• D. If the first statement is correct and the second statement is incorrect

Read each statement and its corresponding reason carefully. Then, analyze the relationship between the two. Choose the correct answer from the options and select the letter of your answer.

Statement A: An orbital with principal quantum number n = 1 can have an angular momentum quantum number l = 1.

Statement B: The principal quantum number defines the general size and energy of the orbital.

• A. Both the statement is correct

• B. Both the statement is incorrect

• C. If the first statement is incorrect and the second statement is correct

• D. If the first statement is correct and the second statement is incorrect

Based on the given properties of the compound and its example. Which of the following pairs is correctly matched?

• CO2 → polar molecule, paramagnetic

• Mg → covalent bond, poor conductor

• CH4 → polar bonds, overall polar molecule

• NaCl → ionic bond, high melting point

Given that ionic compounds form through electron transfer and covalent compounds form through electron sharing, which physical property best distinguishes covalent compounds from ionic ones?

• High melting points, soluble in water

• Electrical conductivity in molten state

• Low melting points, poor conductors

• Metallic luster and malleability

Refer to the diagram. Which statement is TRUE about metallic bonding?

• It involves transfer of electrons between metals and nonmetals.

• It involves shared electron pairs between nonmetals.

• It consists of delocalized electrons forming a “sea” around positive ions.

• It is the weakest type of chemical bond.