Democritus, an ancient Greek philosopher who lived around 460-370 BCE, made significant contributions to the early development of the atomic theory.
His ideas laid the foundation for the later development of modern atomic theory. Here's how Democritus contributed to the atomic theory and the structure of the atom:
Concept of Indivisible Atoms: Democritus proposed that everything in the physical world was made up of tiny, indivisible particles called "atoms." The word "atom" itself is derived from the Greek word "atomos," which means "indivisible" or "uncuttable." Democritus believed that atoms were the fundamental building blocks of matter and that they could not be divided into smaller parts.
Various Shapes and Sizes: Democritus suggested that atoms could vary in shape and size. He proposed that different substances were composed of atoms with different shapes, which explained the diversity of matter in the universe.
Empty Space: Democritus also introduced the idea of "void" or empty space between atoms. He believed that atoms were in constant motion and that the void allowed for this motion.
Lack of Experimental Evidence: It's important to note that while Democritus made these philosophical speculations about atoms, he did not provide any experimental evidence to support his ideas. His atomic theory was largely based on reasoning and thought experiments rather than empirical data.
Democritus' atomic ideas were influential, but they were largely overshadowed by the more prominent theories of his contemporary, Aristotle, which emphasized the existence of four fundamental elements (earth, water, air, and fire). It wasn't until much later, in the 19th century, that John Dalton and others developed the modern atomic theory, which incorporated experimental evidence and refined our understanding of atoms as the smallest units of matter that retain the properties of chemical elements.
Democritus contributed to the atomic theory by proposing the concept of indivisible atoms as the fundamental building blocks of matter, but his ideas lacked experimental support and were not widely accepted in his time.
(2) –1 to –2 (4) +3 to +2
The change that shows an oxidation is the change –1 to +2.
The term oxidation has to do with an increase in oxidation number. This increase will always be positive.
Hence, we have to look out for the change in which there is an increase in oxidation number and this occurs for the change –1 to +2.
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(1) HCl (3) NH3
(2) H2O (4) CH4
Answer:
(4) CH4
Explanation:
When there are no polar bonds in a molecule, there is no permanent charge difference between one part of the molecule and another, and the molecule is nonpolar.
In option A, HCl is not nonpolar because Cl has a pretty high electronegativity of 3.16, the H-Cl bond is polar due to the electronegative difference. This means option A is wrong.
In option B, A water molecule is polar because (1) its O-H bonds are significantly polar, and (2) its bent geometry makes the distribution of those polar bonds asymmetrical. The side of the water molecule containing the more electronegative oxygen atom is partially negative, and the side of the molecule containing the less electronegative hydrogen atoms is partially positive.
In option C, NH3 is polar because it has 3 dipoles that do not cancel out. Each N-H bond is polar because N is more electronegative than H. NH3 is overall asymmetrical in its VSEPR shape, so the dipoles don't cancel out and it is therefore polar.
In option D, CH4 looks like a C in the middle with 4 H's coming off of it. It is nonpolar because the electronegative difference is balanced. The H's all have the same electronegativities, and all cancel out since they are opposite one another.
The correct answer is
Water
:)
Answer: The net ionic equation is written below.
Explanation:
Net ionic equation of any reaction does not include any spectator ions.
Spectator ions are defined as the ions which does not get involved in a chemical equation. They are found on both the sides of the chemical reaction when it is present in ionic form.
The chemical equation for the reaction of nitric acid and sodium hydroxide is given as:
Ionic form of the above equation follows:
As, sodium and nitrate ions are present on both the sides of the reaction. Thus, it will not be present in the net ionic equation and are spectator ions.
The net ionic equation for the above reaction follows:
Hence, the net ionic equation is written above.
Answer : The correct option is,
Explanation :
(1)
(2)
(3)
The reactions 1, 2, and 3 are the example of double-displacement reaction in which the cation and anion of the two reactants exchange their places to give two new compounds.
(4)
This reaction is an example of oxidation-reduction reaction.
Oxidation reaction : It is defined as the reaction in which a substance looses its electrons. In this, oxidation state of an element increases.
Reduction reaction : It is defined as the reaction in which a substance gains electrons. In this, oxidation state of an element decreases.
In this reaction the oxidation state of nitrogen and hydrogen is (0) and the oxidation state of nitrogen and hydrogen in are, (-3) and (+1). So, from this we conclude that the nitrogen shows reduction reaction and hydrogen shows oxidation reaction.
Hence, the correct option is,