Your Question: There are two kinds of elements that didn't appear on the periodic table until after 1892. What kinds are they and why do you think it took so long to discover them?
The Answer: Moseley’s analysis enabled chemists to refine the table further and reveal more gaps, which suggested that there were more new elements waiting to be discovered, with atomic numbers 43, 61, 72 and 75. Scientists subsequently found these elements—now known as technetium, promethium, hafnium and rhenium, respectively.
Explanation: Physicist Henry Moseley discovered the atomic number of each element using x-rays, which led to more accurate organization of the periodic table. We will cover his life and discovery of the relationship between atomic number and x-ray frequency, known as Moseley's Law.
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Answer: The atoms of the solid products are tightly packed whereas those in gas are loose.
Explanation:
Atoms in the solid structure are linked to each other by strong force of attraction and they collectively form an three-dimensional structure. The binding of the atoms form the shape of the solid product. The gas exhibit free atoms in it. The atoms are not linked to one another by strong force of attraction. The atoms as a part of gas have higher energy as those present in the solid products. So, the atoms of the gas wander freely as compared to those in the solid products.
Answer:
Pure substance B) Consists of a single element or type of compound.
Homogeneous A) Mixture that has its different components mixed evenly within the substance.
Heterogeneous D) Mixture that has its different components mixed unevenly within the substance.
Solution C) Liquid homogeneous mixture in which the solute is distributed evenly within the solvent.
Explanation:
Pure substances are a form of matter with definite constant composition and distinct properties. They consist of a single element or type of compound, as can be seen in its formula. Na, O₂, NaCl and H₂O are examples of pure substances.
When 2 or more pure substances are mixed together they form a mixture. If the mixture has its different components mixed <u>evenly</u> within the substance it is a homogeneous mixture. Whereas if the mixture has its different components mixed <u>unevenly</u> within the substance it is a heterogeneous mixture. The different parts observable in a heterogeneous mixture are known as phases.
In liquid homogeneous mixtures, we can recognize one or more substances that are in lower proportions (solutes) and one substance that is in greater proportion (solvent). This kind of mixture is known as a solution.
To determine the volume of both concentration of vinegar, we need to set up two equations since we have two unknowns.
For the first equation, we do a mass balance:
mass of 100% vinegar + mass of 13% vinegar = mass of 42% vinegar
Assuming they have the same densities, then we can write this equation in terms of volume.
V(100%) + V(13%) = V(42%)
we let x = V(100%)
y = V(13%)
x + y = 150
For the second equation, we do a component balance:
1.00x + .13y = 150(.42)
x + .13y = 63
The two equations are
x + y = 150
x + .13y = 63
Solving for x and y,
x = 50
y = 100
Therefore, you need to mix 50 mL of the 100% vinegar and 100 mL of the 13% vinegar.
