Question

1. what is the formula for an ionic compound made of carbon and oxygen? a) c₂o b) co c) co₂ d) co₃ e) carbon and oxygen do not form an ionic compound. 21) what is the name of the ionic compound made of beryllium and chlorine? a) beryllium(ii) chloride b) beryllium chloride c) monoberyllium dichloride d) beryllium dichloride e) none of the above 22) what is the name of cos? a) cobalt sulfide b) cobalt(ii) sulfide c) cobaltous sulfur d) cobalt monosulfide e) none of the above 23) what is the name of the compound whose formula is na₂o? a) disodium monoxide b) sodium oxide c) sodium monoxide d) disodium oxide e) none of the above 24) what is the formula for the phosphate polyatomic ion? a) po₃⁴⁻ b) pho³⁻ c) po₄³⁻ d) po₄¹⁻ e) none of the above 25) what is the name of the molecular compound sf₅? a) sulfur pentafluoride b) sulfur heptafluoride c) monosulfur tetrafluoride d) sulfur hexafluoride e) none of the above 26) what is the correct formula for the molecular compound heptaphosphorus octafluoride? a) p₇f₆ b) p₇f₈ c) p₅f₈ d) p₆f₇ e) none of the above

Explanation:

Step1: Recall ionic - compound formation rules

Carbon and oxygen are non - metals. Non - metals form covalent compounds, not ionic compounds. So for question 20, the answer is E.

Step2: Name ionic compounds of beryllium and chlorine

Beryllium has a + 2 charge and chlorine has a - 1 charge. The compound is $BeCl_2$ and its name is beryllium chloride. So for question 21, the answer is B.

Step3: Name the compound CoS

Cobalt can have multiple oxidation states. In CoS, cobalt has a + 2 oxidation state and sulfur has a - 2 oxidation state. The name is cobalt(II) sulfide. So for question 22, the answer is B.

Step4: Name the compound $Na_2O$

Sodium has a + 1 charge and oxygen has a - 2 charge. The compound is named sodium oxide. So for question 23, the answer is B.

Step5: Recall the formula of the phosphate polyatomic ion

The formula of the phosphate polyatomic ion is $PO_4^{3 - }$. So for question 24, the answer is C.

Step6: Name the molecular compound $SF_5$

The prefix for 5 in naming molecular compounds is penta. The compound is sulfur pentafluoride. So for question 25, the answer is A.

Step7: Determine the formula of heptaphosphorus octafluoride

Hepta means 7 and octa means 8. The formula is $P_7F_8$. So for question 26, the answer is B.

Answer:

1. E. Carbon and oxygen do not form an ionic compound.
2. B. beryllium chloride
3. B. Cobalt(II) sulfide
4. B. Sodium oxide
5. C. $PO_4^{3 - }$
6. A. sulfur pentafluoride
7. B. $P_7F_8$