Answer:
There are no unpaired electrons.
Explanation:
There are no unpaired electrons in the Lewis symbol for a nitride ion(
).The nitride ion has a charge of -3. The negative charge on the Nitride ion indicates a gain in electrons . Nitrogen has 5 valence electrons that is the number of electrons that are in its outer shell .The total number of electrons that the nitride ion has is equal to 5+3 = 8 electrons . Electrons usually appear in pairs and obey the octet rule therefore the nitride ion has four electron pairs no unpaired electrons.
5. 25 x 10⁻⁷mg
Explanation:
This is mass conversion from mg to kg;
The kg is a quantity of mass used to measure the amount of matter in a substance.
Given mass = 5.25 x 10⁻¹³kg
The kilo- is a prefix that denotes 10³
therefore;
1000g = 1kilogram
the milli- is a prefix that denotes 10⁻⁻³
1000mg = 1g
Now that we know this, we can convert:
5.25 x 10⁻¹³kg x 
= 5. 25 x 10⁻¹³ x 10⁶mg
= 5. 25 x 10⁻⁷mg
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A bicycle rusting after it is left in the rain is an example of a chemical reaction because it involves oxidation (Option d).
<h3>What is a chemical reaction?</h3>
A chemical reaction can be defined as a phenomenon in which one or more substances called reactants react to form one or more different compounds, which are known as products.
A chemical reaction may include an enzyme that works to increase the seed of the reaction in normal conditions by lowering the activation energy of the reaction.
Therefore, we can conclude that a chemical reaction such as oxidation in a bicycle is a process where reactants combine or break down to form the products of such reaction.
Complete question:
Which of the following situations contains an example of a chemical reaction?
a. Ice forming after water is placed in a freezer
b. Watercolor paint drying on paper
c. a sugar cube dissolving in a glass of water
d. a bicycle rusting after it is left in the rain
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Answer:
Some metals can be extracted from compounds by heating with carbon atom because they are less reactive than carbon and some metals cannot be extracted because they are more reactive than carbon atom.
Explanation: If the metal is less reactive than carbon atom so the carbon atoms make bond with oxide or other atom present with metal and the metal is free from that oxide or that element. But if the reactivity of metal is higher than carbon is unable to remove the oxide or element.
