Aug 2025 R Chem MC

Which two particles each have a mass approximately equal to one atomic mass unit?

• positron and electron

• positron and neutron

• proton and electron

• proton and neutron

As the electron in a hydrogen atom gains energy and moves from the first shell to the third shell, the hydrogen atom becomes an

• atom in an excited state

• atom in the ground state

• ion in an excited state

• ion in the ground state

Which phrase describes the protons and neutrons in atoms of two different isotopes of the same element?

• the same number of protons and the same number of neutrons

• the same number of protons and a different number of neutrons

• a different number of protons and the same number of neutrons

• a different number of protons and a different number of neutrons

Which phrase compares the properties and molecular structure of oxygen, O₂(g), and ozone, O₃(g)?

• the same properties and the same molecular structure

• the same properties and different molecular structures

• different properties and the same molecular structure

• different properties and different molecular structures

Which phrase describes the composition of a compound?

• different elements physically combined

• different elements chemically combined

• the same element physically combined

• the same element chemically combined

Tags

NGSS.MS-PS1-1

Which quantity is conserved during all chemical reactions?

• density

• molecules

• charge

• temperature

Tags

NGSS.HS-PS1-7

At STP, a 5.0-gram sample of which substance contains metallic bonds?

• CO

• Fe

• KI

• Ne

When a cesium atom becomes a positive ion, there is a change in electron configuration and radius. Which statement describes this change?

• The atom gains an electron, and the radius increases.

• The atom gains an electron, and the radius decreases.

• The atom loses an electron, and the radius increases.

• The atom loses an electron, and the radius decreases.

Tags

NGSS.HS-PS1-1

NGSS.HS-PS1-2

Given the equation representing a reaction:

F + F → F₂

Which statement describes the changes that occur during this reaction?

• A bond is formed as energy is absorbed.

• A bond is formed as energy is released.

• A bond is broken as energy is absorbed.

• A bond is broken as energy is released.

Tags

NGSS.HS-PS1-4

Which atom, in the ground state, has a stable valence electron configuration?

• Bi

• Cs

• Pb

• Rn

Tags

NGSS.HS-PS1-1