Regents 2018 1-33

Which statement describes the location of protons and neutrons in an atom of helium?

• Protons and neutrons are in the nucleus.

• Protons and neutrons are outside the nucleus.

• Protons are outside the nucleus, and neutrons are in the nucleus.

• Protons are in the nucleus, and neutrons are outside the nucleus.

Answer explanation

Protons and neutrons are located in the nucleus of an atom of helium, making the statement 'Protons and neutrons are in the nucleus' the correct choice.

Given a list of atomic model descriptions: A: electron shells outside a central nucleus B: hard, indivisible sphere C: mostly empty space Which list of atomic model descriptions represents the order of historical development from the earliest to most recent?

• A, B, C

• B, C, A

• B, A, C

• A, C, B

Answer explanation

The correct order of historical development for atomic models is B, C, A. Initially thought as hard spheres, then mostly empty space, and finally electron shells around a nucleus.

Which list represents the classification of the elements nitrogen, neon, magnesium, and silicon, respectively?

• nonmetal, metalloid, nonmetal, noble gas

• nonmetal, noble gas, metal, metalloid

• nonmetal, metalloid, noble gas, metal

• noble gas, metal, metalloid, nonmetal

Answer explanation

The correct classification for the elements nitrogen, neon, magnesium, and silicon is nonmetal, noble gas, metal, metalloid respectively.

In the ground state, all atoms of Group 15 elements have the same number of

• valence electrons

• electron shells

• neutrons

• protons

Answer explanation

In the ground state, all atoms of Group 15 elements have the same number of valence electrons, which are the electrons in the outermost energy level.

What is the chemical formula for ammonium sulfide?

• (NH₄)₂S

• (NH₄)₂SO₃

• (NH₄)₂SO₄

• (NH₄)₂S₂O₃

Answer explanation

The correct chemical formula for ammonium sulfide is (NH₄)₂S, as it consists of two ammonium ions (NH₄⁺) and one sulfide ion (S²⁻).

Which formula is an empirical formula?

• N₂O₄

• NH₃

• C₆H₆

• P₄O₁₀

Answer explanation

The empirical formula represents the simplest whole-number ratio of atoms in a compound. NH₃ is the empirical formula as it shows this ratio for ammonia.

Chemical properties can be used to

• determine the temperature of a substance

• determine the density of a substance

• differentiate between two compounds

• differentiate between two neutrons

Answer explanation

Chemical properties can be used to differentiate between two compounds, allowing for the identification of different substances based on their unique characteristics.

Ice, H₂O(s), is classified as

• an ionic compound

• a molecular compound

• a homogeneous mixture

• a heterogeneous mixture

Answer explanation

Ice, H₂O(s), is classified as a molecular compound because it consists of covalently bonded H₂O molecules.

Which phrase describes the molecular polarity and distribution of charge in a molecule of carbon dioxide, CO₂?

• polar and symmetrical

• polar and asymmetrical

• nonpolar and symmetrical

• nonpolar and asymmetrical

Answer explanation

Carbon dioxide (CO₂) is a nonpolar molecule due to its linear shape and symmetrical distribution of charge, resulting in a net dipole moment of zero.

Which element tends not to react with other elements?

• helium

• hydrogen

• phosphorus

• potassium

Answer explanation

Helium tends not to react with other elements due to its stable and full outer electron shell, making it a noble gas.