7. Write some physical properties of non-metals.

1. Lack of Metallic Luster: Unlike metals, non-metals generally lack metallic luster. Instead, they may appear dull or have varying degrees of transparency or opacity.

2. Brittleness: Non-metals tend to be brittle and may shatter or break into irregular fragments when subjected to stress. This is in contrast to the malleability and ductility observed in metals.

3. Low Density: Non-metals typically have lower densities compared to metals. As a result, they often feel lighter and less dense than metals.

4. Low Melting and Boiling Points: Non-metals generally have lower melting and boiling points compared to metals. This means they can undergo changes in state (from solid to liquid to gas) at lower temperatures.

5. Poor Conductivity: Non-metals are generally poor conductors of heat and electricity. Unlike metals, non-metals lack the free electrons necessary for efficient conduction of electrical current and thermal energy.

6. High Electronegativity: Non-metals tend to have higher electronegativity values compared to metals. Electronegativity is a measure of an atom's ability to attract and hold onto electrons in a chemical bond.

7. Varied Appearance: Non-metals can have diverse appearances, ranging from gases (such as oxygen and nitrogen) to solids (such as carbon and sulfur). They may exhibit a wide range of colors, textures, and states of matter under different conditions.

8. Lower Opacity: While some non-metals may be opaque (such as carbon in the form of graphite), many non-metals are transparent or translucent. For example, gases like oxygen and nitrogen are colorless and transparent.

9. Non-Magnetic: Most non-metals are non-magnetic and do not exhibit magnetic properties. However, there are exceptions, such as the non-metal iodine, which can be attracted to magnets in certain forms.

10. Lower Sonorousness: Non-metals typically do not produce the characteristic ringing sound associated with metals when struck. Instead, they may produce a dull thud or no sound at all.

These are some of the physical properties commonly observed in non-metals. It's important to note that while these properties are generally true for non-metals as a group, there can be variations among different non-metallic elements based on their specific atomic and molecular structures.