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cestrela7 [59]
3 years ago
6

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 th

ink it took so long to discover them?
Chemistry
2 answers:
rosijanka [135]3 years ago
6 0

Answer:

The two elements are Argon and Helium .

They are noble gas  and are not reactive

Explanation:

The two kinds of element are argon and helium. These two element were discovered in 1892 by a Scottish chemist Williams Ramsay.

These two elements are known as noble gas or inert gas  because of how hard they find it to react with other elements.

Elements back then were discovered through their reactivity with other elements but It took so long to discover these elements(argon and helium) because of their unreactive nature . Combine with the fact that they were odorless, tasteless and colorless it was more hard to discover them.

Lelu [443]3 years ago
5 0

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.

Remember to read study guides, lessons and notes to rely yourself on; key to success is working hard. Good Luck!

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Electrons in atoms exist in particular energy level. A ___ must be emitted or absorbed to move between energy levels.
svetlana [45]

Answer:

Photon of light

Explanation:

According to Bohr's model of the atom, electrons in atoms are found in specific energy levels. These energy levels are called stationary states, an electrons does not radiate energy when it occupies any of these stationary states.

However, an electron may absorb energy and move from one energy level or stationary state to another. The energy difference between the two energy levels must correspond to the energy of the photon of light absorbed in order to make the transition possible.

Since electrons are generally unstable in excited states, the electron quickly jumps back to ground states and emits the excess energy absorbed. The frequency or wavelength of the emitted photon can now be measured and used to characterize the transition. This is the principle behind many spectrometric and spectrophotometric methods.

8 0
3 years ago
Now molecules:
MArishka [77]

Answer:

a

Explanation:

6 0
3 years ago
With which group would group 18 most likely bond
Mice21 [21]

Answer:

The noble gases (Group 18) are located in the right of the periodic table and were previously referred to as the "inert gases" due to the fact that their filled valence shells (octets) make them extremely nonreactivE

Explanation:

8 0
3 years ago
What is the amount of heat absorbed when the temperature of 75 grams of water increases from 20 to 75
german

Answer:

55°C

Explanation:

original is 20

after gaining heat is 75

75 - 20 = 55

8 0
2 years ago
Read 2 more answers
If 7.25g of chlorine is reacted with excess hydrogen and produces 7.25 g HCl. What is the percent yield?
lozanna [386]

Answer:

94.61 %

Explanation:

percent yield = (actual yield / theoretical yield) X 100%

The balanced equation for the reaction is:

H2 (g ) + Cl2(g) => 2 HCl (l)

So, the theoretical yield =  

 7.25g of chlorine X (2mol of Cl / 35.453 g of Cl) X (2mol Cl / 2mol of HCl) X  37.469g of Hcl / 2mol of Hcl = 0.409 x 18.735 = 7.663g of Hcl

Using this theoretical yield and the provided value for actual yield, the percent yield = (actual yield / theoretical yield) X 100%

= (7.25 g / 7.663g) X 100

= 94.61 %

   

3 0
3 years ago
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