Question

check your understanding

1. name each of the following ionic compounds:

(a) mgbr₂
(b) khso₄
(c) (nh₄)₃po₄
(d) ca(oh)₂

1. name each of the following molecular compounds:

(a) cf₄
(b) ph₃
(c) p₄o₁₀
(d) pcl₃
(e) n₂f₄
(f) o₂f₂

1. copy the following list of compounds in your notebook. identify each compound as ionic or molecular. mark the binary compounds with an asterisk (*). name each compound using the appropriate method.

(a) p₂o₅
(b) caso₄
(c) kno₃
(d) mgi₂

1. write the formula for each of the following compounds:

(a) phosphorus pentachloride
(b) sulfur hexafluoride
(c) nitrogen trifluoride
(d) silicon tetrafluoride
(e) silver phosphate
(f) manganese(ii) dichromate
(g) sodium perchlorate
(h) cobalt(ii) permanganate

1. write the systematic name for each of the following substances:

(a) water, h₂o
(b) ammonia, nh₃
(c) potash, k₂co₃
(d) lye, naoh

1. thinking critically explain why a standard naming system is important for international communication, safety, and efficiency.

Explanation:

Step1: Recall ionic - compound naming rules

For ionic compounds, name the cation first and then the anion. If the cation has multiple oxidation states, use Roman numerals to indicate the charge.

(a) $MgBr_2$

Magnesium is the cation ($Mg^{2 + }$) and bromide is the anion ($Br^-$). The name is magnesium bromide.

(b) $KHSO_4$

Potassium is the cation ($K^+$), and the anion is hydrogen sulfate ($HSO_4^-$). The name is potassium hydrogen sulfate.

(c) $(NH_4)_3PO_4$

The ammonium ion ($NH_4^+$) is the cation and phosphate ($PO_4^{3 - }$) is the anion. The name is ammonium phosphate.

(d) $Ca(OH)_2$

Calcium ($Ca^{2+}$) is the cation and hydroxide ($OH^-$) is the anion. The name is calcium hydroxide.

Step2: Recall molecular - compound naming rules

For molecular compounds, use prefixes to indicate the number of atoms of each element.

(a) $CF_4$

Carbon is the first - named element and there is 1 carbon atom (no prefix for 1). Fluorine is the second - named element with 4 atoms, so the prefix 'tetra' is used. The name is carbon tetrafluoride.

(b) $PH_3$

Phosphorus is the first - named element (no prefix for 1) and hydrogen is the second - named element with 3 atoms. The prefix 'tri' is used. The name is phosphorus trihydride (also commonly called phosphine).

(c) $P_4O_{10}$

There are 4 phosphorus atoms (prefix 'tetra') and 10 oxygen atoms (prefix 'deca'). The name is tetraphosphorus decoxide.

(d) $PCl_3$

Phosphorus (no prefix for 1) and 3 chlorine atoms (prefix 'tri'). The name is phosphorus trichloride.

(e) $N_2F_4$

There are 2 nitrogen atoms (prefix 'di') and 4 fluorine atoms (prefix 'tetra'). The name is dinitrogen tetrafluoride.

(f) $O_2F_2$

There are 2 oxygen atoms (prefix 'di') and 2 fluorine atoms (prefix 'di'). The name is dioxygen difluoride.

Step3: Classify compounds as ionic or molecular and name them

(a) $P_2O_5$

It is a molecular compound. There are 2 phosphorus atoms (prefix 'di') and 5 oxygen atoms (prefix 'penta'). The name is diphosphorus pentoxide. It is binary (two elements), so mark it with an asterisk (*).

(b) $CaSO_4$

It is an ionic compound. Calcium ($Ca^{2+}$) is the cation and sulfate ($SO_4^{2 - }$) is the anion. The name is calcium sulfate.

(c) $KNO_3$

It is an ionic compound. Potassium ($K^+$) is the cation and nitrate ($NO_3^-$) is the anion. The name is potassium nitrate.

(d) $MgI_2$

It is an ionic compound. Magnesium ($Mg^{2+}$) is the cation and iodide ($I^-$) is the anion. The name is magnesium iodide. It is binary, so mark it with an asterisk (*).

Step4: Write formulas for given compounds

(a) Phosphorus pentachloride

Phosphorus is $P$ and pentachloride indicates 5 chlorine atoms. The formula is $PCl_5$.

(b) Sulfur hexafluoride

Sulfur is $S$ and hexafluoride indicates 6 fluorine atoms. The formula is $SF_6$.

(c) Nitrogen trifluoride

Nitrogen is $N$ and trifluoride indicates 3 fluorine atoms. The formula is $NF_3$.

(d) Silicon tetrafluoride

Silicon is $Si$ and tetrafluoride indicates 4 fluorine atoms. The formula is $SiF_4$.

(e) Silver phosphate

Silver has a + 1 charge ($Ag^+$) and phosphate is $PO_4^{3 - }$. Using the criss - cross method, the formula is $Ag_3PO_4$.

(f) Manganese(II) dichromate

Manganese(II) is $Mn^{2+}$ and dichromate is $Cr_2O_7^{2 - }$. The formula is $MnCr_2O_7$.

(g) Sodium perchlorate

Sodium is $Na^+$ and perchlorate is $ClO_4^-$. The formula is $NaClO_4$.

(h) Cobalt(II) permanganate

Cobalt(II) is $Co^{2+}$ and permanganate is $MnO_4^-$. Using the criss - cross method, the formula is $Co(MnO_4)_2$.

Step5: Write systematic names

(a) $H_2O$

The systematic name is dihydrogen monoxide (but commonly called water).

(b) $NH_3$

The systematic name is nitrogen trihydride (but commonly called ammonia).

(c) $K_2CO_3$

Potassium is the cation ($K^+$) and carbonate is the anion ($CO_3^{2 - }$). The name is potassium carbonate.

(d) $NaOH$

Sodium is the cation ($Na^+$) and hydroxide is the anion ($OH^-$). The name is sodium hydroxide.

Step6: Explain the importance of a standard naming system

A standard naming system is important for international communication, safety, and efficiency because:
- **International communication**: It allows scientists around the world to communicate about chemical substances clearly, regardless of their native language. Everyone can understand the composition and properties of a substance from its standard name.
- **Safety**: In industries such as pharmaceuticals, manufacturing, and chemical handling, knowing the exact identity of a substance is crucial for safety. Standard names prevent confusion that could lead to accidents.
- **Efficiency**: In research and development, a standard naming system helps in quickly identifying and referencing substances, making the scientific process more efficient.

Answer:

1.

• (a) Magnesium bromide
• (b) Potassium hydrogen sulfate
• (c) Ammonium phosphate
• (d) Calcium hydroxide

2.

• (a) Carbon tetrafluoride
• (b) Phosphorus trihydride (phosphine)
• (c) Tetraphosphorus decoxide
• (d) Phosphorus trichloride
• (e) Dinitrogen tetrafluoride
• (f) Dioxygen difluoride

3.

• (a) *Diphosphorus pentoxide (molecular)
• (b) Calcium sulfate (ionic)
• (c) Potassium nitrate (ionic)
• (d) *Magnesium iodide (ionic)

4.

• (a) $PCl_5$
• (b) $SF_6$
• (c) $NF_3$
• (d) $SiF_4$
• (e) $Ag_3PO_4$
• (f) $MnCr_2O_7$
• (g) $NaClO_4$
• (h) $Co(MnO_4)_2$

5.

• (a) Dihydrogen monoxide
• (b) Nitrogen trihydride
• (c) Potassium carbonate
• (d) Sodium hydroxide

1. A standard naming system is important for international communication (enables global scientific communication), safety (avoids confusion in industries), and efficiency (speeds up research and development).