Question

which statements are true concerning covalent bonds?
select two correct answers.

a. covalent bonds form between metals and nonmetals.

b. covalently bonded compounds have high melting and boiling points.

c. covalent bonds form through the donation of electrons.

d. covalently bonded compounds usually have low melting and boiling points.

e. covalent bonds form between two nonmetals.

the table below shows properties of four substances.

substance	melting point (°c)	good conductor?
2	32.0	no
3	123.2	yes
4	1102.3	no

which substance could be glass (a polar, covalently bonded compound)?

a. 1

b. 2

c. 3

d. 4

Explanation:

First Sub - Question (Covalent Bonds True Statements)

• Option A: Ionic bonds form between metals and nonmetals, not covalent bonds. So A is false.
• Option B: Covalently bonded compounds (molecular) usually have low melting and boiling points. Ionic compounds have high melting/boiling points. So B is false.
• Option C: Covalent bonds form through sharing of electrons, ionic bonds through donation. So C is false.
• Option D: Covalent (molecular) compounds have weak intermolecular forces, so low melting/boiling points. This is true.
• Option E: Covalent bonds form between two nonmetals as they share electrons. This is true.

Step 1: Recall Properties of Covalent Compounds

Covalently bonded compounds (like glass, a polar covalent compound) are not good conductors (since they don't have free ions/electrons) and have melting points that can be relatively high (glass melts at high temp) but not as high as ionic/metallic. Also, they are not good conductors.

Step 2: Analyze Each Substance

• Substance 1: Melting point 1548.1°C, good conductor. Likely metallic (metals are good conductors, high melting points). Eliminate.
• Substance 2: Melting point 32.0°C, not a good conductor. Too low melting point for glass (glass melts at higher temp). Eliminate.
• Substance 3: Good conductor. Covalent compounds are not good conductors. Eliminate.
• Substance 4: Melting point 1102.3°C, not a good conductor. Matches properties of a covalent (polar, like glass) compound (highish melting point, non - conductor).

Answer:

D. Covalently bonded compounds usually have low melting and boiling points.
E. Covalent bonds form between two nonmetals.

Second Sub - Question (Substance as Glass)