Worksheet: Elements, Atoms, and Molecules

In this worksheet, we will practice defining elements, atoms, and molecules and using these terms in the context of materials and physical processes.

Q1:

What is the difference between a sulfur atom and a sulfur molecule?

  • ASulfur atoms can be divided into smaller units, while sulfur molecules cannot.
  • BSulfur atoms consist of multiple sulfur molecules bonded together.
  • CA sulfur molecule consists of multiple sulfur atoms bonded together.
  • DSulfur atoms are reactive, while sulfur molecules are not.

Q2:

Which of the following best describes a molecule?

  • AA single atom of an element
  • BA mixture of different elements
  • CAtoms of two or more elements bonded together
  • DAtoms chemically bonded together in a discrete unit

Q3:

Which of the following best describes an element?

  • AA substance made from more than one type of atom
  • BA pure substance
  • CAny of the fragments that make up a molecule
  • DThe name shared by atoms containing the same number of protons

Q4:

Which of the following is true of an element?

  • AYou can divide up an element into infinitely many pieces.
  • BElements are made of at least two types of atom, bonded together.
  • CAll the atoms of an element have the same number of protons in their nuclei.
  • DElements in the periodic table are arranged in order of increasing mass.
  • EAll elements are found in nature in their pure states.

Q5:

Which of the following is not an element?

  • AUranium
  • BIron
  • CSteel
  • DMolybdenum
  • ECarbon

Q6:

Which of the following is true for molecules?

  • AOnce you make a molecule out of atoms, you cannot get the constituent atoms back.
  • BMolecules have crystalline structures.
  • CMolecules are distinct, covalently bonded collections of atoms.
  • DAll molecules are composed of more than one type of atom.
  • EAll molecules are made of multiple atoms, all of the same type.

Q7:

What is the symbol for an atom of the element chlorine?

  • ACl
  • BCl+
  • CCl
  • DCl2
  • ECl2

Q8:

What is the symbol for molecular oxygen?

  • AO3
  • B2O
  • CO
  • DO3
  • EO2

Q9:

Which of the following is not a molecule?

  • ACO2
  • BO2
  • CNO
  • DNa
  • EN2

Q10:

What state symbol is used to represent a gas in a chemical equation?

  • A(g)
  • B(gas)
  • C(O)2
  • D(air)
  • E(gs)

Q11:

What state symbol is used to represent a solid in a chemical equation?

  • A(sl)
  • B(s)
  • C(sd)
  • D(solid)
  • E(sld)

Q12:

What is the total number of atoms in the following molecule?

CCHOHHH

Q13:

Thionyl chloride is a gas with the chemical formula SOCl2. Which diagram could represent pure SOCl2?

  • A
  • B
  • C
  • D
  • E

Q14:

What state symbol is used to represent a liquid in a chemical equation?

  • A(aq)
  • B(HO)2
  • C(l)
  • D(lq)
  • E(w)

Q15:

Carbon can be burned in excess oxygen to form carbon dioxide according to the following equation. C()+O()CO()sgg22

How many different elements, atoms, and molecules are present in this equation?

  • AElements: 2, atoms: 3, molecules: 2
  • BElements: 2, atoms: 6, molecules: 2
  • CElements: 3, atoms: 2, molecules: 6
  • DElements: 3, atoms: 2, molecules: 3
  • EElements: 6, atoms: 3, molecules: 3

Q16:

The diagram shows a small number of carbon dioxide and water molecules, with blue circles representing an atom of oxygen. How many atoms of carbon, hydrogen, and oxygen are present in the diagram?

  • A10 carbons atoms, 3 hydrogen atoms, and 8 oxygen atoms
  • B10 carbons atoms, 8 hydrogen atoms, and 3 oxygen atoms
  • C8 carbons atoms, 3 hydrogen atoms, and 10 oxygen atoms
  • D3 carbons atoms, 10 hydrogen atoms, and 8 oxygen atoms
  • E3 carbons atoms, 8 hydrogen atoms, and 10 oxygen atoms

Q17:

The energy required to turn liquid chlorine (Cl())2l into gaseous chlorine (Cl())2g is +20.4 kJ/mol. The energy required to split a molecule of chlorine into two chlorine atoms is +242 kJ/mol. Which of the following statements explains the difference between these two values?

  • AThere are more chlorine atoms than there are chlorine molecules.
  • BThe bonds connecting the chlorine atoms are covalent bonds.
  • CStronger forces exist between chlorine molecules than the bonds connecting the chlorine atoms in each molecule.
  • DThe bonds connecting the chlorine atoms are much stronger than the forces that exist between chlorine molecules.
  • EChlorine is already a gas at room temperature and pressure.

Q18:

Which statement correctly classifies the chemicals in the following equation as either a solid, a liquid, or a gas? NaCO()+2HCl()NaCl()+CO()+HO()2322saqaqgl

  • ASolid: NaCO23, liquid: HCl, NaCl, gas: CO2
  • BSolid: NaCO23, liquid: HO2, HCl, NaCl, gas: CO2
  • CSolid: NaCO23, liquid: HO2, gas: CO2, HCl, NaCl
  • DSolid: NaCO23, liquid: HO2, gas: CO2
  • ESolid: NaCO23, liquid: none, gas: CO2

Q19:

Oxyacetylene torches produce temperatures in excess of 3,000C. Under these conditions, acetylene burns completely according to the following equation: 2CH+5O4CO+2HO22222.

What state symbol can be applied to all the components of this reaction under these conditions?

  • A()g
  • B()aq
  • C()s
  • D()l

Q20:

Which of the following statements about elements is false?

  • AThe atoms in the element are covalently bonded.
  • BElements are made of only one type of atom.
  • CElements cannot be broken into simpler forms.
  • DElements are pure substances.
  • EThe atomic mass of the element is the average mass of the protons and neutrons.

Q21:

What is the chemical symbol for elemental sodium?

  • AS
  • BNa
  • CN
  • DNa
  • EN2

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