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givi [52]
3 years ago
15

What is the atomic number of the element shown? O A. 26 B. 27.0 C. 40.0 D. 13

Chemistry
1 answer:
Fynjy0 [20]3 years ago
8 0
The answer is 40.0 atomic number .
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Please Help!
Whitepunk [10]

We can use two equations for this problem.<span>

t1/2 = ln 2 / λ = 0.693 / λ
Where t1/2 is the half-life of the element and λ is decay constant.

20 days = 0.693 / λ 
λ   = 0.693 / 20 days        (1) 

Nt = Nο eΛ(-λt)                (2)

Where Nt is atoms at t time, No is the initial amount of substance, λ is decay constant and t is the time taken.
t = 40 days</span>

<span>No = 200 g

From (1) and (2),
Nt =  200 g eΛ(-(0.693 / 20 days) 40 days)
<span>Nt = 50.01 g</span></span><span>

</span>Hence, 50.01 grams of isotope will remain after 40 days.

<span>
</span>

3 0
3 years ago
Colorea los recuadros que representan la acciones viables para usar racionalmente los recursos y contaminar menos
In-s [12.5K]

Algunas acciones viables para utilizar los recursos ambientales de forma racional y con el objetivo de reducir la contaminación son:

  • Ahorra agua y energía
  • Reducir, reciclar y reutilizar los residuos generados en el hogar.
  • Reducir el uso de vehículos de combustión interna.
  • Usa energías renovables
  • No quemes basura al aire libre
  • No utilices aerosoles ni frigoríficos que dañen la capa de ozono.
<h3 /><h3>¿Qué importancia tiene la sostenibilidad?</h3>

Es fundamental para la preservación y mantenimiento del medio ambiente y la calidad de vida de las generaciones actuales y futuras. El desarrollo de acciones sostenibles promueve la protección del medio ambiente, los ecosistemas y los recursos naturales.

Por lo tanto, todas las personas e instituciones económicas pueden promover la sostenibilidad a través de prácticas fáciles de ejecutar que ayuden a preservar y proteger el medio ambiente.

Encuentre más información sobre sostenibilidad aquí:

brainly.com/question/23701037

7 0
2 years ago
Alkaline earth metals do not react with oxygen. true or false
elena-s [515]
False. Alkaline earth metals react with oxygen.
3 0
3 years ago
I need all the answers 16-25
vladimir1956 [14]
16. Metals have a structure containing delocalised electrons, meaning they can conduct electricity as they allow movement of charged particles.    17. groups of elements (columns) react in the same way, but depending on whether they group tends to lose or gain electrons the reactivity can increase or decrease when going down the group (column)     18. O2 is non polar as there is no difference in electronegativity between two oxygen atoms (they are the same). CO2 is non polar, it has polar bonds (O is more electronegative than C) but as it is symmetrical there is no polarity in the molecule.     19. Water is polar as the lone pairs on the O repel the delta + H groups so that the HOH angle is around 109deg, so water molecules create polar interactions which each other. These polar interactions require energy to break, so water has a higher boiling point than other small molecules which don't have these interactions.      20. The metal used is tough, and the horseshoe is usually heated meaning the metal will act slightly more viscous (closer to liquid). This means it can be moulded better, and then when its cooled it will become stronger and more brittle.       21. Well N2 + H2 --> NH3, by the haber process, so nitrogen:hydrogen ratio is 1:3. But what they want you to say is that nitrogen has 5 electrons and hydrogen has 1 and you're aiming for eight so you need N (5) + 3 Hs (3*1=3) to make NH3 (8 electrons around N)       22. Na and H, as this reduces the valence shell number and therefore reduces the energy state of the atom       23. Ar, its very stable as its octet is filled, meaning to fill or empty its octet it would have to lose or gain 8 electrons which is extremely hard        24. Oxygen, as it would accept the electrons donated by the 2 Na atoms, and fill its octet while emptying both the Na's     25. N2 and O2 are both covalently bonded, Oxygen forms a double bond to itself like this O=O and nitrogen forms a triple bond to itself like this N<span>≡N </span><span>Hope that helps :) and make sure you learn this, it'll come back and bite you when you need it for a test</span>
8 0
3 years ago
Read 2 more answers
A vial is filled with room temperature water, and blue cold water has been placed at the bottom. A warm water bag sits next to t
MrRa [10]

Explanation:

In the context, a vial which is used in store medical samples is filled with water at room temperature. And the vial is kept on a cold water. Also a water bag containing warm water is kept near the vial.

The cold water kept at the bottom of the vial is having lower kinetic energy while warm water will have higher kinetic energy than the others. Since the water in the vial is at room temperature and it is in touch with the cold blue water, the water in the vial will loose or give its temperature to the cold blue water through conduction as well as convection process since temperature always flows from a hot body towards the cold body.

On the other hand, the warm water placed next tot he vial will give its temperature to the atmosphere.  

5 0
3 years ago
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