Answer:
Carbon atoms in graphite and diamond are arranged in different ways. Hence, the two allotropes of carbon have different physical properties.
Explanation:
Both graphite and diamond are both made of only carbon atoms. However, their physical properties differ from each other. Hence, they are called allotropes. Think about how these carbon atoms are arranged in each of the allotropes.
<h3>Graphite</h3>
In graphite, each carbon atom is bonded to three other carbon atoms. These carbon atoms will be located in the same plane. A chunk of graphite can contain many of these planes.
Each carbon atom has four valence electrons. Three of these electrons will be used in the bonds. The other electron will be delocalized. These electrons would flow between the sheets of carbon atoms. That keeps the sheets separate and allow them to slide on top of each other.
<h3>Diamond</h3>
In diamond, each carbon atom is bonded to four other carbon atoms. These carbon atoms will form a tetrahedral network.
In graphite, there's a significant separation between two adjacent sheets of carbon atoms. The force between the two sheets is rather weak. When a piece of graphite is between two objects that move over one another, the layers in the graphite would also slide over one another. Since the attraction between two adjacent sheets isn't very strong, there wouldn't be much resistance. Hence the graphite acts as a lubricant.
In contrast, most of the carbon atoms in a piece of diamond would be connected to each other. Unlike the sheets in graphite, in a diamond there are almost no moving parts. Also, the forces between neighboring carbon atoms are very strong. When an external force acts on a chunk of diamond, the carbon atoms would barely move. Hence, the structure appears to be very rigid. That gives diamond its abrasive properties.
Answer: Option (3) is the correct answer.
Explanation:
Aerobic organisms are the organisms which survive and grow in the presence of oxygen.
When oxidation of glucose occurs in the presence of oxygen then it is known as aerobic respiration.
In aerobic respiration, food releases energy to produce ATP which is necessary for cell activity. There is complete breakdown of glucose in aerobic respiration that is why more energy is released. Therefore, aerobic organisms become active.
Thus, we can conclude that characteristics very active, efficient use of energy describes aerobic organisms.
Selenium is a non metal, radon is a noble gas, silicon is a metalloid, and sulphur is a non metal. Hafnium is a transition metal.
<u>Answer:</u> The correct answer is Option 1, Option 2 and Option 3.
<u>Explanation:</u>
A base is defined as the substance which releases hydroxide ion when dissolved in water.
For the given options:
- <u>Option 1:</u>

When ammonia is dissolved in water, it produces ammonium hydroxide which forms a basic solution.

- <u>Option 2:</u>

When sodium oxide is dissolved in water, it produces ammonium hydroxide which forms a basic solution.

- <u>Option 3:</u>

When lithium hydroxide is dissolved in water, it produces aqueous lithium hydroxide which forms a basic solution.

- <u>Option 4:</u>

When phosphorus pentoxide is dissolved in water, it produces phosphoric acid which forms an acidic solution.

Hence, the correct answer is Option 1, Option 2 and Option 3.