Answer:
- <em>He realized that some elements had not been discovered.</em>
Explanation:
Some scientists that tried to arrange the list of elements known before Mendeleev include Antoine Lavoisier, Johann Döbereiner, Alexandre Béguyer de Chancourtois, John Newlands, and Julius Lothar Meyer.
<em>Dimitri Mendeleev</em> was so succesful that he is recognized as the most important in such work.
Mendeleev by writing the properties of the elements on cards elaborated by him, and "playing" trying to order them, realized that, some properties regularly (periodically) repeated.
The elements were sorted in increasing atomic weight (which is not the actual order in the periodic table), but when an element did not meet the pattern discovered, he moved it to a position were its properties fitted.
The amazing creativity of Mendeleev led him to leave blanks for what he thought were places that should be occupied by elements yet undiscovered. More amazing is that he was able to predict the properties of some of those elements.
When years after some of the elements were discovered, the genius of Mendeleev was proven because the "new" elements had the properties predicted by him.
d. exothermic; leaving
- Exothermic reaction is a reaction that produces heat in the reaction whereas the endothermic reaction is a reaction in which heat is required to be given in the reaction to produce product.
- Fire is an exothermic reaction.
- A fire is produced due to oxidation of the fuel in the form of liquid or gas.
- A fire is an example of combustion.
- In fire both heat and light are left from fire due to the oxidation of fuel.
Hence, option d. exothermic; leaving is the correct option.
Learn more about fire:
brainly.com/question/12761984
Answer:
Mg(OH)2 + 2HCI ⇒ MgCI2 + 2H2O
Explanation:
In order to balance a chemical equation you need to make sure both sides of the equations are equal.
Mg(OH)2 + 2HCI = MgCI2 + H2O
Mg = 1
Oh = 2
HCI = 2
Products:
Mg = 1
CI = 2
H = 2
O = 1
2H20 = 1 × 2 = 2
2 × 2 = 4
2HCI
1 × 2 = 2
Mg(OH)2 + 2HCI ⇒ MgCI2 + 2H2O
Hope this helps.
Answer:
C) Modernization of humans
