Subatomic Particles

A molecule of water (H₂O) consists of two hydrogen atoms and one oxygen atom. Which of the following best describes a compound?

• A substance made of only one type of atom

• A combination of elements that can be easily separated

• A mixture of different substances not chemically bonded

• A substance formed by chemically combining two or more element

Which statement best defines an element based on its composition and chemical properties, distinguishing it from compounds and mixtures?

• A pure substance consisting of only one type of atom.

• A blend of different atoms and molecules.

• A substance created by chemically joining two or more elements.

• A combination of substances that are not chemically bonded.

  Which of the following is the best definition of an element?

• a pure substance made of one type of atom

•   a mixture of different types of atoms and molecules

•   a combination of substances not chemically bonded

• a substance formed by combining two or more elements

Which statement correctly describes the charge and location of protons, neutrons, and electrons?

• Protons are positive and located in the nucleus; electrons are negative and orbit the nucleus; neutrons are neutral and orbit the nucleus.

•    Protons are neutral and located in the nucleus; electrons are negative and orbit the nucleus; neutrons are positive and orbit the nucleus.

•    Protons are positive and located in the nucleus; electrons are negative and orbit the nucleus; neutrons are neutral and located in the nucleus.

• Protons are negative and located in the nucleus; electrons are positive and orbit the nucleus; neutrons are neutral and located in the nucleus.

Two elements, X and Y, are in the same column of the periodic table, but X has a lower atomic number than Y. Based on this information, which prediction is most likely correct about their properties?

•     Element X has more protons than element Y, making it more reactive

• Element Y has a larger atomic radius because it has more electron shells.

• Both elements have different numbers of valence electrons, leading to different reactivity.

• Element X and Y have identical properties because atomic number does not affect reactivity.

   Carbon-12 and Carbon-14 are isotopes. Which of the following correctly describes the role of neutrons in these atoms? Neutrons                           

• add negative charge to the atom.

•   determine the element’s identity.

• determine the number of electrons in the atom.

•   help stabilize the nucleus by balancing proton repulsion.

  How do electrons contribute to the formation of chemical bonds? Electrons                                    

  

•   have no role in chemical bonding.

•   in the nucleus attract other atoms.

• determine the number of protons in an atom.

• are transferred or shared between atoms to form bonds.

Potassium (K) has an atomic number of 19. Which of the following correctly describes the chemical behavior of potassium?

• It has 19 protons.

• It has 19 electrons in a neutral atom.

• It belongs to Group 1, the alkali metals

• It has 19 neutrons and is highly reactive.

Element Y is found in Period 4 of the periodic table. Scientists predict that this element will behave similarly to other elements in its group. Based on its period number, which of the following best explains a key factor influencing its chemical behavior? The key factor influencing its chemical behavior is the number of

• protons

• neutrons

• electron shells

• valence electrons

Why are valence electrons important in chemical reactions?

• They define the atomic mass of an element.

• They interact with other atoms to form bonds.

• They remain unchanged during chemical reactions.

• They determine the number of protons in an atom.