Structure of Matter

How many atoms are needed to form a molecule?

Answer explanation

Atoms form molecules that range in size from two to thousands of atoms.

The following molecule was used to show a molecule of methane, or CH4. Describe the number and type of each component of the molecule.

Answer explanation

In each methane molecule, there are four hydrogen atoms and one carbon atom.

Methane (CH4) combines with Oxygen gas (O2) to form carbon dioxide (CO2) and water (H2O). Describe the number and type of atoms for a molecule of each substance. 

Answer explanation

For each molecule in methane, there are four hydrogen atoms and one carbon atom. In oxygen gas, there are two oxygen atoms per molecule. In carbon dioxide, there are two oxygen atoms and one carbon atom per molecule. In water, there are two hydrogen atoms and one oxygen atom per molecule.

What is the difference between an atom and an element?

Answer explanation

An element is a pure substance that cannot be broken down into simpler substances. An atom is the smallest particle of an element maintaining the chemical identity of that element.

Which of the following is true about how hydrogen and oxygen can combine to form molecules?

• Two atoms of hydrogen are always required to bond with two atoms of oxygen.

• Molecules composed of hydrogen and oxygen must have at least four atoms.

• Hydrogen and oxygen can combine in many ways to form different molecules.

• When oxygen combines with hydrogen to make a molecule, water will always be produced.

Which of the following best explains the relationship between molecules and atoms?

• Atoms have smaller parts, called molecules.

• Molecules are atoms that have no mass.

• Atoms are molecules that have a charge.

• Molecules are made up of two or more atoms.

The extended structure of sodium chloride (NaCl) is shown. Which of the following best describes the configuration of Layer 4 of the sodium chloride crystal?

• It will contain 4 atoms of chlorine and 5 atoms of sodium.

• It will have sodium that are bonded only to other sodium atoms.

• It will be identical in all of its characteristics to Layer 1.

• It will have chlorine atoms in all four of its corners.

Students are asked to create models of molecules using marbles of different colors to represent atoms of different types. Below is a table describing the models made by four students. Which of the following is the most accurate evaluation of these models?

• All of the students created acceptable models because molecules can consist of many different configurations of atoms.

• All student models are acceptable except that of Student 4, since molecules can’t be made of so high a number of atoms.

• Only students 1, 2, and 4 created acceptable models, since molecules must be made of different types of atoms.

• Only Student 2 created an acceptable model of a molecule, since every molecule must have a balance of atoms.

Atomic models of graphite and diamond are shown. Graphite is a soft, dark material often used as a lubricant. Diamond is often a clear, hard crystal. Which of the following best explains the difference in these materials?

• The elements of which each one is made

• The size and shape of the individual atoms

• The arrangement of the atoms of each one

• The number of atoms each one is made of

Match the following

• Crystal

• The basic building block of matter; made of electron(s), proton(s), and
    neutron(s)

• Atom

• The smallest unit of a compound

• Substance

• Solid material whose atoms are arranged in an ordered pattern

• Molecule

• Anything with both volume and mass

• Matter

• Matter with consistent properties throughout