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Homework Practice

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Atoms and Molecules: From Particles to Formulae

Section A: Core Ideas

Question 1mcq
Which option correctly identifies oxygen gas, O2O_2?
A.An ion of a salt
B.A molecule of an ionic compound
C.An atom of a compound
D.A molecule of an element
Question 2mcq
Which substance is a molecule of an element?
A.NaClNaCl
B.H2OH_2O
C.N2N_2
D.CO2CO_2
Question 3mcq
Which property is commonly associated with ionic compounds such as sodium chloride?
A.They never dissolve in water.
B.They are made of oppositely charged ions.
C.They are always made of single neutral atoms.
D.They contain only molecules of one element.
Question 4mcq
Which ion is a cation?
A.Na+Na^+
B.O2−O^{2-}
C.SO42−SO_4^{2-}
D.Cl−Cl^-
Question 5mcq
An atom has electronic configuration 2,8,12,8,1. Which ion is it most likely to form?
A.+3+3 ion
B.Neutral molecule only
C.−1-1 ion
D.+1+1 ion

Section B: Application Practice

Question 6mcq
What is the correct formula of magnesium chloride if magnesium has valency 2 and chlorine has valency 1?
A.MgClMgCl
B.Mg2Cl2Mg_2Cl_2
C.MgCl2MgCl_2
D.Mg2ClMg_2Cl
Question 7mcq
Which formula uses the correct convention for water?
A.H(2)OH(2)O
B.H2OH_2O
C.h2oh2o
D.HO2HO2
Question 8mcq
Which matched pair is correct for atoms molecules and compounds?
A.NaClNaCl — compound
B.HeHe — molecule of a compound
C.O2O_2 — atom of a compound
D.H2OH_2O — element
Question 9mcq
Which substance is best described as a covalent compound molecule?
A.ArAr
B.O2O_2
C.NaClNaCl
D.CH4CH_4
Question 10mcq
Which pair is most likely to form an ionic compound?
A.Carbon and hydrogen
B.Nitrogen and nitrogen
C.Sodium and chlorine
D.Oxygen and oxygen